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Reglsfcrod' at the G.P.O., Sydney, for transmisjlon by

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PLANS-"TEMPEST" & "FIREFLY"

PAGE II. RADIO AND HOBBIES IN AUSTRALIA JUNE, 1945

THE KEY TO A Successful(areer

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HOBBIES AUSTRALIA j«?igna'^gruv! . '•:::r:_-.i; :' >: '• .■" •• " ; ' ' "i:':' jill

European f-âral(e

GREAT BRITAIN entered the Euro- pean war with bombs weighing

a few hundred pounds,, and a mere handful of planes. She emerged with 10-ton "earthquakes" and a vast air fleet.

That age-old plaything of inventors —the explosive rocket — was trans- formed by German scientists into a 12- ton "V" weapon, which came hurtling through the stratosphere to land, without warning, on Allied cities. These same rockets, in another guise, have imparted enormous hitting power to small planes flying at anything up to 500 mph.

There have, indeed, been developments all along the line and every one is a tribute to the resourcefulness and

efficiency of modern science when turned to the task of shedding blood. It seems likely that more has been accomplished in the six odd years of World War II, than in any other corresponding period.

But more significant than the mere development of weapons is the fact that, for the first time in history, nations are equipped with the means to intrude and smash one another, with little reference to the so-called front line. Germany's ultimate fall was brought about, as much as anything, by the devastation of her cities and war plants.

If International logic matches scientific development, we will hasten to learn the lesson of the past six years. We will realise that any future conflict will be initiated by crippling blows dwarfing Rotterdam and Pearl Harbor, blows that will shatter the wellbeing of multitudes. The devastation evident in Europe even now is surely bad enough.

Once the Pacific war has concluded, we owe to our children nothing less than a framework to ensure lasting peace; one which will direct science into better channels. More than mere politics is at stake!

INDEX^

Japs Won't Liice "Ten Ton Tessie This Plane Smashed The Robombs Peering Into Davy Jones' Locler . Punled?—This Is How It Works . Talons For The Fleet Air Arm .. . These Planes Are Making History . Science On The March

Page .. 3

4 6 9

10 12 13

Television In Theory & Practice . .. 15 Jap Radio Is Well Constructed .. 21 Problems Of Sound Reproduction . . 22

Pago Complex Waves & Their Applica-

tion 25 More About Transformer Coupling 30 Radio's Wartime Progress 33 Broadcast Band DX 34 Short-Wave Notes—By Ted Whiting 35 This Month's Recordings 39 A Solid Model Of The Aquitania . . 40 Technical Editor's Book Review . . .. 42 Answers To Correspondents .43

McGILL'S RADIO COLUMN RADIO

CokI. Post G rammer—A.R.R.L. Course In

Badiu Fundamentals .. .. 5/- .. 3d Kellaway—A Radio Dictionary 2/- .. 2d Rider—Cathode Ray Tube at

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Sturley—Radio Receiver Deslrn, Vol. l . ... 36/- .. 4d Admiralty—Manual of Wireless

Telegraphy. Vol. 1 .. 7/- .. Sd Admiralty—Manual of Wireless

Telegraphy. Vol. II 10>6 .. 4d A.R.R.L.—Antenna Handbook .. 4/6 .. 3d Chamberlain — Marine Radio Operators' Guide 8/- .. Sd Cocking — Wireless Servicing

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Camera Annual 36/- .. 4d Richardson—lUuebook of Pro- jection, 7th Edition 50/- .. Gd

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Warwick & Tunslall—First Aid to the Injured and Sick .. 6/3 .. 3d

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riage 9/6 .. 4d Stopes—Wise Parenthood .. .. 9/6 .. 3d

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Charlesby & Perkins—A Practi- cal Course in Magnetism, Elec- tricity and Radio 11/- .. 4d Richtcr—House Wiring 12/- .. Sd

Thomas—Electricity /for Be- ginners 12/- .. Sd Date—Electrical Technology for Telecommunications 8/- .. Sd

MISCELLANEOUS Henley—20th Century Book of

Ten Thousand Formulas. Pro- cesses and Trade Secrets .. 82/- .. 6d Bennet—Formulas for Profit .. 10/- .. 4d

Brentz—Story of the Earth and Stars 8/8 .. 4d Yates—Model Making .. .. .. 24/- 4d

Hall—How to Use the Micro- scope 5/6 .. 4d E.U.P.—Teach Yourself Book- keeping 4/6 .. Sd

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PAGE TWO RADIO AND HOBBIES FOR JUNE, 1945

FEATURE STORY

JAPS WONT LIKE "TEN TON TESS1E"

As the war in Europe draws to a close, the RAF is using a bomb weighing 22,0001b. (almost 10 tons). Production of this huge bomb, nicknamed "Ten Ton Tessie," is one of the most remarkable engineering feats of the war, involving many new ballistic problems. It is 10,0001b. heavier than the

previous'biggest.

WHEN contrasted with the bombs

used early in the war, t o d a y's manuhoth "earthquake bombs" reveal the amazing developments that have taken place in five-and-a-half years.

At the outbreak of the war, the biggest bomb produced by any ordinance factory 1 n Britain was the 500- pounder, but a very big proportion of the bombs at the disposal of the RAP Bomber Command were mere 250-pounders.

However, it was soon found that larger mis- siles were much more "economical." It was established that, pound for pound, bigger bombs were more effective. The destructive power of one 5001b bomb was found to be considerably

Thii as* t«r made by ihc ten-ton bomb at an experimen- tal eilablishment in

England.

..,4 -

».

Tnev have also been used against small ships, the force of their explosion causing artificial tidal waves, which wrecked vessels within a wide radius.

Tests to prove the effect of the ^.OOO-pounders' blast were carried out on old buildings in remote parts of Britain. Explosives were improved and means were perfected by which the whole charge was detonated In one instantaneous explosion. The quantity of TNT, which is the basic explosive charge of the bomb, was stepped up, and a new "super" explosive, known as RDX, was introduced.

EFFECT OF BLAST Blasts from these bombs obliterates

everything within a big radius. Blast comes from the sudden and tremendous displacement of air which follows the explosion of the bomb, causing compression of the atmosphere into a density so high that It strikes with the force of a solid material. Then, with the blast effect expended, there is an inrush of air as pressures readjust themselves. This is also extremely destructive. Finally comes the fire, which is fanned by the movement of the displaced air.

The problem of stowage was one of the factors which influenced the de- cision to provide the blockbusters with thin-walled casings. Blockbusters were designed with a much squatter shape than smaller types, to make it easier to stow them in the deep bomb-bays of the aircraft. The whole balance of the huge bomb in the aircraft had to be settled when the blockbuster was on the drawing-board.

Another stowage problem concerned the means of suspending the bomb in the machine while in flight. The utmost care had to be exercised in the

(Continued on Page 5)

more than that of two 250-pounders; that of a 1000-pounder many times that of two 500-pounders, and so on.

Steadily the size of bombs was increased. In 1940 the 1000-pounders appeared, followed by 2000-pounders. The first 4000-pounders were dropped in 1941; then in 1943 came the 8000- pounders, and early last year the first 12,000-pounder.

With the 12,000-pounder came a new development in bomb design. It was shown by ballistic tests that destructive power was increased by using a thinner casing and a heavier weight of high explosive. Reliance was placed on the effect of blast rather than that of the fragmentation of the bomb.

With the 1000-pounders, the explosive content was just under 38 per cent, of the total weight, the remainder of the weight being taken up in the heavy casing.

With the 2000, 4000 and 8000 pounders, the destructive charge was Increased sharply, reaching a proportion of from 70 to 75 per cent, of the total weight.

The 12,000-pounder has been proved to have terrific powers of obliteration. Many successes were scored with them. They sank the Tirpltz, penetrated the 15ft thick concrete roofs of U-boat shelters, and made craters more than 100 feet across rail-tunnel entrances.

*

The initial stage in thi tion factory in Englani

production of the now ten-ton bomb at an aircraft produc- . It is cast around the framework on which is wound rope

mode from wood shavings.

RADIO AND HOBBIES FOR JUNE, 1945 PAGE THREE

FEATURE STORY

* * ■■ :■< mm

»«, e *

At the height of the robomb blitz, Britain came to light with a new fighter, appropriately named the Tempest. Manned by crack pilots, the plane drew much of the sting from the Nazi V weapon, then turned to the attack over tne beaches and

fields of France on D-day.

ONE Tempest wing, ably led by Wing-Coinmander Roland

Beaumont, DSO, DFG, accounted for the greatest number shot down by any one wing, destroying over 670 "squirts."

Victories have also been recorded against the new Messerschmltt Me 262 jet-propelled aircraft, and Tempests have had great success in all their attacks on enemy occupied Europe.

The Tempest is the latest of a long line of prominent .aircraft, and should indeed be an outstanding machine. It was designed by Sidney Camm and the same team who earlier produced the Hurricane, Tornado and Typhoon.

The lastnamed plane, which has de- monstrated its value as a ground sup- port fighter, may well be regarded as the forerunner of the Tempest.

Actually the Tempest has been referred to as the world's most formidable slngle-engined fighter, and the fastest ever seen in Britain. Just how it compares in this regard to the Mus- tang and the latest Spitfire is not clear, but the top speed of all three is apparently well up toward the 450 mph mark.

Like the Typhoon, the Tempest is of all-metal construction and all surfaces are metal covered, with the ex- ception of the fabric covered rudder. In general, the Tempest resembles the Typhoon, and uses the same pow.er- plant, the 24-cyllnder, sleeve valve, Napier "Sabre," of more than 2200 hp.

' The fuselage, however, has been lengthened by 21 inches, this altera-

tion being brought about by the re- moval of some of the fuel tankage from the wing to the fuselage.

The area of the fixed fin has been increased to compensate for the extra fuselage area forward of the centre of gravity, and also to counteract the compressibility effect, which occurs in high speed dives at, and above, the speed of Sound.

Another radical change from the

Typhoon is the incorporation of the elliptical wing, which has proved so highly successful on that other thoroughbred of the air, the Spitfire.

Elliptical wings seem to be in the fashion nowadays, for we find two other prominent Allied fighters proudly vaunting them. 1 refer, of course, to the Republic Thunderbolt, and the Royal Navy's new two-seat fleet fighter, the Fairey Firefly.

Incidentally, It is stated that another version of the Tempest is powered With the Bristol Centaurus sieeve-valva radial of over 2000 hp. The Typhoon was often mistaken by spotters, Who confused it with the Thunderbolt, so the Tempest with a radial engine and similar wing outline may cause many headaches for identification experts.

THIN WING-SECTION Another feature of the Tempest wing

Is the very thin airfoil section. In spite of this, however, the four 22mm. cannons have been neatly tucked in, leaving very small muzzles projecting from the leading edge, and with four tiny "blisters" on the upper surface. The thin section reduces frontal area considerably and should therefore In- crease the speed.

A four-bladed de Havllland constant speed airscrew is fitted and -the latest versions of the Typhoon also Incor- porate this modification. Great attention has been paid to streamlining, and the clean lines of the Tempest are a pleasure to see. All unnecessary ex- crescences have been removed, the remainder being carefully faired over.

The tail wheel retracts and is closed in by two doors, while the main undercarriage legs (which are identical with those of the Typhoon) are also completely faired off by two flaps. Smooth surface camouflage paint is used, in contrast to the rough, drab finish of earlier British war-planes.

The cockpit canopy has been short- ened slightly In comparison with that of the Typhoon, and has beeh ballooned to improve the downward vision, a very necessary feature of a fighter aircraft.

By

Walter

Judd

Though the wingj of the Tempest ere un- usually thin, the designers have managed to pack in (our 20mm. cannon and a goodly stock of ammunition. Mech- anics are shown loading the guns.

PAdE FOUR *ADIO AND HOBBIES FOR JUNE, I94|

FBATVRB STORY

Color scheme, which may be of interest to model aircraft enthusiasts, follows the latest British practice. All tipper surfaces are dark sea grey and dark green, while under surfaces are a medium sea grey.

The centre section of the wing, from just inside the aileron to the fuselage on each side of the aircraft, are marked on the under surface with ''Invasion" stripes. These consist of four narrow black and three broad white bands each side.

A light grey spinner and fuselage band (which completely circles the fuselage, with its front edge on the leading edge of the fixed fin) add a touch of color. Airscrew blades, exhaust ports and undercarriage legs. &c., are dull black.

Regular British insignia are carried, and the squadron lettering is in light grey, while the individual aircraft number is in gloss black.

Principal dimensions of the Tempest are: Span 41ft., length 33ft. 8in., height with tail up and ■ one airscrew blade vertical is 14ft. lOin., while the height with tail down and one blade vertical is f6ft. fin.

JAPS WON'T LIKE TEN-TON TESS1E' I (Continued carrying and release of such a huge quantity of high explonve.

It was found that, in order to make it possible for the aircraft to be manoeuvred violently without throwing out-o'f-balance stresses on the suspension mechanism, the holding points had to be evenly distributed above the centre of gravity. *

When the r2,000-pounders were found satisfactory, bombers were built with the special lacks required for the job.

Now bomb weights have increased no less than 10,0001b, in one jump. The new 22,000-pounder is 35ft. long, with a diameter of 3ft. lOin. It is the most destructive weapon yet devised by man,

Avro "Lancasters" have teen modi- fled for the 22,000-pouriders, and a new type of bomb trolley and special hoist- ing tackle have been introduced. It takes six men half an hour to load it, A runway of three miles is required for the plane's, take-off.

C»«AiNSi 81 W T HAWCtK, TE.MPE.3r

from rage 3) . | Some idea of the way in which the

conceptions of bombing have changed can be gained from the fact that the 22,0001b. bomb which a Lancaster can now deliver to Germany is heavier than the entire Vickers Wellington twin-engined bomber, which was the only really useful bomber available to Britain when war broke out in 1939, Weight of the Wellington, empty, was 18,5001b,

PENETRATES DEEPLY The new 22,0001b. missile is reported

to combine great piower of penetration, with the explosive force of a blast bomb. It is suggested that it will be particularly valuable in destroying underground factories and underground "towns," such as the Germans established to escape Allied bombing.

There is a marked contrast between the new British bonjbs and the German V-weapons. The British bombs are dropped on their targets by bomb aim- ers with the utmost accuracy, whereas V-bombs can only be aimed hap- hazardly, And. although the Nazi long- range rocket weighs 12 tons in all, the great proportion is taken up in pro- pellant fuels and intricate mechanism, so that the true explosive charge is of one ton only.

Development of Britain's huge new bombs is mainly the work of Mr. B. N. Wallis, of Vickers Armstrong, who •pent many years on problems of aircraft design before the war. Before the 12,000 and 22,000 pounders were a practical reality, Mr. Wallis produced the special bombs, which breached the Eder and Mohne dams He is one of 20 candidates nominated for fellowship of the Royal Society,

Wallis first proposed the 10-tonner five years ago, but only recently has it become possible to use the bomb as he first designed it. From plans of the 10-tonner. a smaller bomb was made, because, until the arrival of the Lan- caster, it was not possible to use anything as big as Wallis had planned.

And now, some of the men who did so much to "write off" Germany's oil, aircraft and communication centres, are planning the unleashing of huge bomber fleets against Japan. It may not be long now before the RAP will be sending "Ten Ton Tessies" crashing down on Japanese war factories.

SIXTY THOUSAND! Specifications of nearly eo.ooo

aircraft of all nationalities have been compiled by D. D. Hatfield, an engineer employed by Fairchild Aerial Surveys Inc., of Los Angeles. He started to collect information in 1931, and, in addition to listing the various aircraft, he has built up a library of 25,000 negatives of photographs of aircraft and an equal number of drawings and sketches. He is at present engaged in the task of copying his original files by photography for assembly into volume form, A limited number of sets of volumes are to be presented to interested museums. He estimates that the specifications will fill 60 1000- page volumes. Pile prints of his library of negatives are being prepared for the Los Angeles Public Library.

RADIO AND HOBBIES FOR JUNE, 1945 PAGE FIVE

POPULAR S CIE N C t '

NTO DAVY OKR L

Nearly three-quarters of the surface of our earth is occupied by ocean. We have charted its currents and its navigation hazards, but have explored little of its real depths. Consider- able knowledge has been gained by indirect methods, but a strange new realm may lie revealed to the scientist who ultimately overcomes the barriers of pressure and darkness

in the mighty valleys of the sea.

feet It is about 15,0001b. per square inch. This is quite a tidy pressure and, as can be imagined, is capable of doing quite a bit of damage to a human body. ,

The floor of the ocean is divided up by mountains, plains and valleys similar to the land surface; the magnitude of the mountains and valleys of the ocean floor are enormous, however; more so than on land.

The depth varies from shallow bays to enormous valleys of over 30,000 feet in depth. Near the island. of Guam in the North Pacific Ocean is a "Deep" called the Challenger Deep, of 31,614 feet or 66 feet less than six miles. This can be compared with the highest mountain in the world, Mt. Everest, which is 29,002 feet high.

One of the most interesting aspects of the study of the ocean is the life that exists at different depths and the deposits on the floor of the ocean.

These deposits are divided into two classes: First, those made up of debris from the land surface and occurring in close proximity to shorelines; these are called Terrigenous deposits. The second type are the deposits laid down in the abysmal depths of the ocean and called Pelagic deposits.

TYPES OF DEPOSIT

YES there are about 140 million is almost uniform in regard to the around the land from the snore ro smiare ini les of ocean anil on I v* ratio of chemicals in solution, the a depth of about 100 fathoms; they

-i ,j .?i- oiean ami only saiinity varies considerably both along consist mainly of gravel, sand, and ol odd million square nnles of land. the sl/rfaCe and vertically mud. Only part of this is habitable, so as with any other liquid contain- As we proceed out to sea from an we can understand the tendency ing salts in solution, the salinity is average depth of 100 fathoms, the of nations to push one another increased by evaporation and lowered deposits change in character, the "overboard" at the first opportunity, by dilution with fresh water. amount of land debris gradually de-

We In Australia would he lout, with- Thus, in regions of the Red Sea creasing and the remains of once living

The Terrigenous deposits form is almost uniform in regard to the around the land from the shore to

We in Australia would be lost with-

CeLh on'whlSi0 tobe^me0 sunbufnerL eê T^r T ^ rnn- than elsewhere by reason of the

and the Mediterranean and in the organisms gradually becoming more oceans immedaitely north and south evident. of the equator, the water is saltier The Terrigenous deposits are sub-

either! Apart from the direct con- tribution the sea makes to our daily diet, it provides us with the climatic conditions which make, possible our very existence.

The cycle of rainfall and evaporation Itself provides an Interesting study. However, this article is intended to deal more with what the sea contains rather than what it does.

Pure sea water is normally colored a light shade of blue, .but it may occur in many different shades of green or brown," due to the color of living organisms or suspended matter. There is no need to enlarge on the point that sea water is salt, as many a sailor has found when he has tried to use it in his whisky.

greater evaporation. In most cases, a greater amount of water is lost by

divided into various muds. There is the predominant Blue Mud near the land; next comes the Green Mud found

evaporation than can be replaced by, near continents which rivers and rainfall, and the salts In solution thus become more concentrated.

The surface water of the Atlantic Ocean flowing into the Mediterranean contains about 3 .6 % | of salts, but, as the j » # water removed by ( IS V ^ evapotation is j • greater than the 1 SAf supply of fresh [ WWI water, the salinity ! soon rises to about i——— 3.8',.

In coastal areas, where the rivers

By Calvin

Walters

The chemical composition of sea carry into the sea a greater volume water has been carefully determined. Almost all the known elements are found in solution but the majority of them are in such minute quantities that they may be disregarded for all practical purposes.

The solid matter constitutes about 3.5% of the total and the main chemicals in solution are Sodium Chloride (common salt), Magnesium Chloride, Magnesium Sulphate, Cal- cium Sulphate, Potassium Sulphate Calcium Carbonate, Magnesium Bromide, Of these, Sodium Chloride is by far the most plentiful, constituting about 77% cf the total. Al-

of water than is evaporated from it, the salinity is decreased. Vertically, the salinity decreases with depth so that, taking an average of 3.6%. salinity at the surface, the greater part of the deeper water is about 3 45 3 saline.

One often hears of the great pressure that exists in the depths of the ocean. Pressure so great that man cannot descend very far, and fish brought from the deep water have exploded on reaching the surface.

The pressure increases by about 15 pounds per square inch for every 30 odd feet in depth of water so that, 31 3000 feet the pressure is about 1500

though the composition of sea water pounds to the square inch; at 30,000

coasts, then Volcanic Mud, and, finally, Coral Mud.

The Pelagic deposits are divided into various Oozes, Firstly, the Globigerina

Ooze, so-called be- i cause it consists of

i ■' the dead shells of ■ • } surface fish called

j by that name. This j ooze is found In j average depths of

LHCITS j 2000 fathoms. i About 20 species

' ' ' of foraminifera are found on the surface waters of the tropical oceans and their dead shells are found in this ooze. Pteropod Ooze is found in the shallower waters, but well away from land, as on ocean ridges and mountains, and especially near coral reef areas. The ooze resembles GlobigeMna Ooze, except that there is a predominance of Mollusca shells ishells from oyster-like fish).

Diatom Ooze is made up of the dead bodies of the minute Diatoms, an organism that flourishes abundantly in the colder regions of the ocean. These Diatoms are microscopic in size, so it can be imagined just how many countless millions of them are required to make an evident deposit on the floor of the ocean.

PAGE SIX RADIO AND HOBBIES FOR JUNE, 1945

POPULAR SCIENCE

The last Ooze to be considered is the 1 Radiolarian Ooze, which Is found in 1 the deep waters of the tropical Pacific 1 and Indian Oceans. (

The surface waters of these oceans i have a low salinity and carry clayey matter. The Radiolarlan, by the way, 1 is another species of organism that 1 exists in sea water in the areas men- i tioned and their dead bodies sink to ] the bottom to form the deposit. 1

The most widely distributed of all deep sea deposits is a Red Clay, which occupies nearly the whole of the deeper abysses of the ocean floor beyond about 2700 fathoms. It occurs in its most 1

characteristic form in the centre of the Pacific a long way from any land surfaces.

The basis of these Red Clay deposits ; is hydrated silicate of alumina, mainly derived from decomposed and disintea- rated pumice and other types of volcanic rocks, which have been exposed for centuries to the action of sea water.

The reddish or chocolate color is due to the presence of manganese and iron oxides. Interesting relics of shark teeth and the ear bones of whales, some of which are from extinct species, are found in profusion in the Red Clay deposits. Some of these pre found coated with the peroxide of manganese and iron and are in a good state of preservation. f

Also found are metallic pieces from ^ interstellar space; they are more evident in the red clay deposit owing to the comparatively small deposits of other materials. Radio-active sub- stances, too, are found in more abundance than in any other deep sea deposit or in land rocks.

LIVING CREATURES What of the living things of the sea?

Marvellous as is the sea with its waves and tides, its currents and waterspouts, many times more marvellous is the variety of its teeming life.

The mountains and plains of the ocean can be likened to a vast house of many floors, each floor of which is represented by the different depths of water, and on which live different Worlds of creatures.

The vegetation on the ocean bed is as diverse as the vegetation in the forests of dry land, and, amid the jungle and tpush of the ocean, there live great denizens of the deep and tiny forms of life, which use the marine vegetation for sustenance and protection, just as do land animals.

There are living creatures called in- fusoria so tiny that a single drop of water may contain thousands of them. Their dead bodies and shells form the various oozes spoken of earlier. In fact, the great chalk and limestone deposits built-up under England and elsewhere have been formed by the de- positing of the shells and bodies of these microscopic creatures over countless millions of years.

Marine life is classified upwards from the microscopic animalcula through sponges, coral, anemones, starfish, molluscs, worms, crustaceans, fish, turtles, dolphins, sâls, and on to the largest known animal, the whale.

So prolific is the breeding of these living creatures that in spite of continuous fishing for many centuries, and

the toll taken from the sea daily by birds, and the preying upon each other, the supply is not diminished. That is, except in those places where I go fishing!

Nature has provided for all this in that fish lay millions of eggs in the breeding season, and it offers protection to the eggs by making them transparent and floating. Then, of course, there are many areas of the sea that are not touched by fishermen and trawlers, so that the reserve is always very great.

One of the questions most frequently asked is "What fish if any live in the abysmal depths of the ocean?"

This is s question that has occupied the minds of many expeditions and attempts have been made to trawl the extreme ocean depths; this has

Experiments have borne out this assumption and in the cruise of the Challenger and later the Norwegian expedition Michael Sars it was found that the sea floor below 2000 fathoms was alfftost a barren wilderness. After repeated trawllngs of hours in extent, the hauls consisted mainly of shells, sharks' teeth, ear bones of whales, a few worms, pumice stone and lumps of clay. ,

There certainly are a few fish and a few only at these depths but It has been concluded that these are more or less migratory; moving along from less deep water. The species called Macrurus seems to predominate; this is a fish some 23 centimetres in length.

In depths of less than 2000 fathoms, however, there is an abundance of fish in keeping with the greater abundance of food available. Even 2000 fathoms is still pretty deep, so that the fish can be truly called deep sea fish.

The number of fish trawled in the two expeditions mentioned decreased from land towards the

Ocean deposih abound with j minute organisms and di- 1 atoms which ar© seen to be j of almost fantastic shape j under a powerful microscope, j The one illustrated on the left is just one of many ]

hundreds. I ( ( Illustrated below is the most | prolific inhabitant of the very deep waters, a species

, of Macrurus. The sketch is a little less

HIISv than half-siie.

been and still is a most formidable task Sot the following reasons.

Approximately two-thirds . of the ocean floor is covered by more than 2000 fathoms of water; this forms a plain of over 905 million square miles in extent, which is nearly half the surface of the earth. The problem of trawling this area is obviously very great.

Then again, it must be remembered that trawls function, not only while being towed along the bottom, but also when being raised end lowered; hence it is necessary to distinguish between organisms living at the bottom , and those from intermediate depths.

As the bottom of the ocean in great depths consists largely of Red clay, it is reasonable to suppose that suitable food for the sustenance of fish is scarce. The obvious assumption is that there are few living', organisms of any size in the deepest parts of the ocean.

abysmal plain; an average trawl up to 500 fathoms was 300 fish; to 1000 fathoms 90 fish; to 2000 fathoms 40 fish, and below this mostly one or two.

It was also established that different species of flsh inhabit the different depth levels so that each strata had its own peculiar community. Other kinds of animals, such as seals, whales and the lower forms of life abound mainly in the shallower water.

It has often been mentioned that some flsh have light producing organs that act as a form of headlight to show the fish "the way home."

While this is true, the function of the light organs of animals has been the sub.iect of controversy for many years. It has been proved that these

(Continued on Next Page)

RADIO AND HOBBIES FOR JUNE, 1945 PAGE SEVEN

The arrival in Australia of Lancastrian mail planes marks the re-opening of a direct air route to Great Britain. Throughout the past five years, air services to the Mother Country have been greatly affected by the changing fortunes of war, being

interrupted altogether at one stage.

AVIATION

AIR ROUTE TO BRITAIN DAVY -tones

LOCKER (Continued from Prevfous

specially OI fish inhabiting tne upper 250 lathoms ol water. This is a surprise, lor it would be reasonable to suppose that the fish living in the lower

1 regions wculd find the greatest use for'such a device: light does not

■BwHm penetrate below a depth of 500 fathoms IWHBRR and. lieiow that, it is dark as night.

T he power of emitting light is found NlgSS&fRI |H in most marine animals and plants, ■RBHBWBBp..including the bacteria. The light in

JjSi animals emanates from glandular structures which secretes a slimy, luminous substance. There is usually a layer of black pigment around the structure which acts as a reflector.

Hie moie highly organised grcups S have light organs of greater com-

plexity, such as rows of luminous cells • M or a transparent lens through which SSggSmSiimmmmSSSmSm^BSSmmSmBSSSSSmSmmSSSBSSm^^mmmmmmmmmmm the light is concentrated. These lens

i. r . . '.< • > ■ certainly suggest that the light is The ornval in Australia of Lancastrian moil planes marks the intended to be projected in certain re-opening of a direct oir route to Great Britain. Throughout directions but for what purpose, has .. . ?. ■ . . . ■ ., , ■ i not been established. Is it to illuminate the post five yeors, oir services to the Mother Country hove the surrounding water, to avoid been greatly affected by the changing fortunes of war, being enemies or to recognise their own

interrupted altogether at one stage. nof Le^hfoimdS.Wer t0 thiS ^

-THK I-ancaslnau ■ is actually a ^ ^^^ên the f Jnh

dy ^ ^leâbysmalbdeX6 ha^

I dirccl adaplalrou of the l.an- ^43 "^11 the RAP intiodueed 110 liKht-emitting organs? Perhaps easier bomber, which will carry on a sei.vice with Cat.ailnas from it is because there is nothing to see, the sei vice until sullicieul Amo oeylon to Western Australia. On July ''J® theie must be rathei dieary. Yorks are available. n,' 1943, this service was taken over In, th€ clu'et a."d dai'k, d®Pt,hs one.

The slim fuselage of the Lancaster by Qantas Empire Airways, under ^0culd ^pe" the ^-v deeo selfish

■was designed to carry only concen- charter to BOAC, being extended m ®0- Most ol she veiy deep sea nsn trated loads, and it lacks the roomi- November, 1943, to Karachi. have very large eyes but others have ness essential for a passenger and mail Meanwhile the air connection from ^ oâi plane. However, it carries nine pa.s- the United Kingdom to the Middle eVtv, the Ln=fh m hf bend sengers, plus mail, has a maximum East was increased by a service with to one-fifth the length of its head. speed of 310 mph, and an all-up weight Liberator Ill's, and later by Sunder- vadicty nc CYCC of nearly 30 tens lands. Liberator Ill's were also intro- vmmci i wr c 1 ca

Until June, 1940, the Empire service duc®d u"der Qa»tas for the Perth- Fish have all kind of eyes. There followed the normal route, via Mar- Cey on hop are stalked eyes, like those of a snail, seilles, Rome, Brindi-si, Athens, Cairo, .™e. cessation of hostilities in Europe but this form seems to be confined Tiberias Habbaniva Basra Bahrein wl" h'66 'he Western half of the to the larval stages of a fish's life Babai Karachi through India to Cal- route from restriction, but the service and bccurs mostly in the upper layers cutta Akvab Rangoon Bangkok over 0,r around 'he Indian Ocean will of water, where most of the? trans- Penang Singapore, Dutch'East Indies be subject to the dictates of the parent fish live. There are telescopic to Darwin and" thence to Sydney. Japanese war. eyes, which are found only in fish

wuh ,k~ ~rur„ m- Ttain info +h«. war from depths of less than 250 fathoms on June 11 1940 an alternative route 811,3 eyes n105'^ P01"' upwards. Tlrese to Fevut was broueht into oneration telescopic eyes occur only in fish that

lUâbandonment"" 0' ' ' tHRNHI TT f »="«« A For a while civil air communica- they are blind in the daytime. It

tions between the United Kingdom Jm / ' seems that the efTiciency and size of and Egypt were severed. Durban be- ^ the eyes of fish decreases with the came the western terminus of the vAf depth. The chief excepUon is the Empire flying-boat service, and the , . Marcrurus. which has very large eves, only connection with the United King- ^ 4.,,and well developed, dom was by ship to the Cape, Tlie mm&fJUj/*'Attempts to explain this have been air link was re-established 111 August, made and it has even been suggested 1040 Him*. that there may be a possible source On August fi a flying-boat service 4 of light other than sunlight, for bottom was inaugurated from the United fishes have 110 light-emitting organs. Kingdcm to Lagos, via Lisbon. Bathurst There Is an interesting possibility in and Freetown, This linked up with ^Jljl-L the knowledge that invertebrate the BOAC route across Central Africa. .J| Jft I • organisms such as worms and other Disturbances in Iraq and Syria in the such things have the power of emitting summer of 1941 caused temporary dis- •*•<"*■-><»■■■ ■>.light. It is just possible that the light organisation of the route onwards to ' ' M -'xfrom these may be strong enough to

Prom October 12, 1941, until March ^ about; a cheap way of getting light. 7, 1942. a flying-boat service was ^ Uke reading a book by the glow from operated through the Mediterranean ^ "le nex' door neighbor's window, to Cairo, providing a .shorter link on ^ There is no space to enlarge on this the United Kinadom-Indla section. In ^ v, most interesting subject. The facts late January, 1942. due to the Japanese I• (ihJI <, I explained may interest you sufficiently advance, the service had to terminate k ® 1 10 ■seek out some bdoks on the matter at Rangoon, and on February 13 at wtnL* V 2 and' should vou do so, I can assure .Calcutta ■»!** </ Jfessfe .vou that there are many hours of

Thereafter, there was ho air link kaMMBaBBaBMiaBMawMaaaManJI absorbing reading in store for you.

THK Tanoaslnaii is aclnally a dirccl adaplalinu of tlic Lan-

cuslcr honiber, which will carry on the service until suirieicul Avro Yorks are avaiiahle.

The slim fuselage of the Lancaster ■was designed to carry only concentrated loads, and it lacks the roomi- ness essential for a passenger and mail plane. However, it carries nine passengers, plus mail, has a maximum speed of 310 mph, and an all-up weight of nearly 30 tens.

Until June, 1940, the Empire service followed the normal route, via Mar- seilles, Rome, Brindi-si, Athens, Cairo, Tiberias. Habbaniya, Basra, Bahrein, Babai, Karachi, through India to Cal- cutta, Akyab, Rangoon, Bangkok, Penang, Singapore, Dutch East Indies to Darwin and thence to Sydney.

With the entry of Italy into the war on June 11, 1940, an alternative route to Egypt was brought into operation, but only a few flights were made on this route, as the fall of France forced its abandonment.

For a while civil air communications between the United Kingdom and Egypt were severed. Durban became the western terminus of the Empire flying-boat service, and the only connection with the United King- dom was by ship to the Cape, The air link was re-established in August, 1940.

On August 6 a flying-boat service was inaugurated from the United Kingdcm to Lagos, via Lisbon, Bathurst and Freetown, This linked up with the BOAC route across Central Africa. Disturbances in Iraq and Syria in the summer of 1941 caused temporary dis- organisation of the route onwards to India.

From October 12, 1941, until March 7, 1942, a flying-boat service was operated through the Mediterranean to Cairo, providing a shorter link on the United Kingdom-India section. In late January, 1942. due to the Japanese advance, the service had to terminate at Rangoon, and on February 13 at

.Calcutta. Thereafter, there was no air link

over the Empire route between the United Kingdom and Australia until May 3, 1943, when the RAF introduced a direct service with Catalinas from Ceylon to Western Australia. On July II, 1943, this service was taken over by Qantas Empire Airways, under charter to BOAC, being extended in November, 1943, to Karachi.

Meanwhile the air connection from the United Kingdom to the Middle East was increased by a service with Liberator Ill's, and later by Sunder- lands. Liberator Ill's were also introduced under Qantas for the perth- Ceylon hop.

The cessation of hostilities in Europe will free the Western half of the route from restriction, but the service over or around the Indian Ocean will be subject to the dictates of the Japanese war.

PAGE EIGHT RADIO AND HOBBIES FOR JUNE, (945

• FEATUki STORY

PUZZLED?—THIS IS HOW IT WORKS

THE "WEASEL" CARRIER CAN GO ANYWHERE

Developed for specialised tasks in today's mobile warfare, the British-designed and American-built cargo-carrier M-29 eon operate on practically any type of terrain, and can drive through water. This amphi biou* craft hat been named the "Weasel"

because of its ability to move swiftly and stealthily on land or water.

WITH a spacious flotation body, the Weasel has long, and parti-

cularly wide driving tracks of the endless-band type. The segments carry shallow paddle studs for water-borne propulsion.

The vehicle seemingly skims over the ground like the animal alter which it is named.

It can operate in snow, deep slither- ing mud, swamp land or shifting sand, with almost the same ease as on paved highways. It is capable of use under a greater variety of terrain conditions than any other vehicle yet produced.

The Weasel has been officially described as being "designed for Arctic reconnaissance and for commando raids."

Key to the vehicle's ability to negotiate surfaces Impassable to conventional wheeled vehicles and even to other track-laying vehicles is its light weight, combined with its broad tracks.

The distribution of weight over such a considerable area gives the Weasel a featherweight "tread."

WEIGHT DISTRIBUTION This distribution is all-important to

the progress of vehicles over soft surfaces. The foot of a man may press the ground about 81b to the square inch when he is standing, and 121b when he is walking. Lorry wheels bear on the ground with a pressure that may be 1001b to the square inch. The track of a normal caterpillar-type vehicle bears less than 61b to the square inch.

In the case of the Weasel, details have not been revealed, but it is conceivable that its weight may be distributed to little more than lib or so to the square inch.

Sketched here is the latest model reported, the M29-C, which shows improved hull design.

The Weasel is being used to good effect as a cargo and personnel carrier, and also for bringing in wounded men. In Europe, Weasels have been reported as going up and down between oppos- ing Are to carry the wounded to hospital.

A powerful engine is mounted in the front of the vehicle, beside the driver's position. Behind is open space for cargo or seating accommodation.

The centre of gravity is low, enabling the machine to negotiate particularly stiff pinches without over- turning.

Inventor of the Weasel is Mr. Geof- frey Pyke who, when Britain's plight was critical, conceived the idea of a vehicle that could be dropped from the air in Norway and other snow-clad regions; a vehicle by which the Ger- mans could be attacked where their own transport was Inferior.

Fyke's plan met with poor response at first, being rejected or neglected

W

nv OF ONE

FOR STEERING VWltlf WHEN WATER-BORSI

aswfls,

10T 6

ft jsaja- RO

until Admiral Lord Louis Mountbatten, then Director of Combined Operations, approved of it.

As Britain's resources were fully taxed at the time, it was agreed that the United States should take over research into the design and manufacture of the vehicle. Now on the

Western Front and in Italy the Weasel has proved itself an extremely valuable transport unit.

As one commentator has stated: "The Weasel has made it possible to carry men and goods under conditions which hitherto remained outside the calculations of military plans."

| RECENT PLASTIC DEVELOPMENTS AN adhesive which can be used

instead of rivets or screws in certain applications is Plastilock 500, developed by Goodrich for bonding metals, wood, plastics and ceramics to themselves or to each other. Metal- to-metal bonds have shown a shear strength of 3250 psl, and tension strength of 4000 psl have been reached. Heat varying from 2B0 degrees P. to 350 degrees P., and sufficient pressure to ensure good contact is required to make a strong bond.

* * * Polystyrene bottles contain hydro-

fluoric acid safely and without de- terioration of the bottle, as in the case with ordinary glass.

★ * * To prevent rust and salt-water cor-

rosion in transit to the battle front, some US fighter planes are enclosed in a single piece of pliofilm, which covers the plane from nose to rudder tab. This waterproof rubber hydro- chloride (made by Goodyear Tyre and Rubber Co., of Akron, Ohio) Is said to be more effective in this application than the earlier method of coating the plane with grease, for two reasons: (1) it is impracticable to apply grease to all of the plane parts; (2) the grease

has to be removed upon the plane's delivery to the scene of action, In- volving expenditure of time and labor.

* * i * Successful perforrhance is reported

by American Viscose Corp., New York. NY, of inner flying gloves made or rayon, which enable the flier to handle instruments and maps at high altitudes or in sub-zero weather Without incurring "cold burn" or freezing of the fingers. The rayon gloves are worn under conventional heavy flying gloves, which can be removed when the occasion demands, leaving the hands protected from intense cold by the rayon.

★ * ★ Installed on drop-hammers In Cur-

tiss-Wrlght airplane plants are tools for working sheet metal that combine a plastics punch with a metal die. In making this tool, no machining is required. The plastics punch is first roughly shaped to mating contour. The metal die is heated to about 370 degrees P.; the punch is then placed on the heated die and pressed into It, pressure forcing the plastics to flow into the heated die, Thus, in a Single operation the punch is shaped to a perfect fit with the die.

RADIO AND HOBBIES FOR JUNE, 1945 PAGE NIN6

AVIATION ♦

TALONS FOR THE FLEET .AIR ARM

-

■>:" v W'

."t

With the entry of the British Fleet into the Pacific theatre, it is only natural that interest will centre on the Fleet Air Arm and the aircraft it will inevitably employ in strikes against Japanese-held territory. Most recent addition to the ever-growing list is the Fairey Firefly, two-seat reconnaissance fighter.

DESIGNED and built by the Fairey Aviation Corp., the

Firefly is a conventional low-wing type conforming with modern design practice.

It bears a hereditary resemblance to the Fulmar, but is somewhat larger in general dimensions and boasts cleaner lines.

The name Firefly is a carry-over from the original single-seat biplane fighter of some 20 years ago, an improved model of which was sold to the Belgian Government. The plane put In a brief, but hectic, appearance in the fateful days preceding the col- lapse of^ Belgium.

The present Firefly has all the ear- marks of a thoroughbred, and gave an exceptionally good account of itself when it first went into action against the German battleship Tirpitz and the land defences protecting that long- harried ship.

GRIFFON MOTOR Powerfully engined with the Rolls

Royce Griffon, the Firefly may be presumed to have an exceedingly good top speed. This, in conjunction with its well-proved armament, should make it more than a match for air opposi- tion other than from the fastest of the single-seat fighters.

Originally, the plane was to have been a single-seater, but, due to the complexity of Air Arm duties, it was finally resolved to make it a two- seater. leaving the flying and fighting to the pilot, and the navigation, reconnaissance, radio, &c., to the observer. So far there seems to have been two distinct types put out, the most notable difference being in the style of exhaust ejector nozzles for the Griffon engine and in the front cockpit canopy; the cannons also are fitted

with streamlined fairings in the later models.

The front cockpit canopy is now higher in front, somewhat on the lines ot that used in the Spitfire. It bulges outwards slightly from the general lines of the fuselage, and so affords a certain amount of rearward and sideways vision for the pilot. The small rear-vision mirror mounted on the apex of the canopy is a further help in this regard.

Ey J.

Finneran

Production of the Firefly follows a growing practice in British manufacture of utilising the group system. Hun- dreds of major and minor firms assist the parent company, each working on a sub-contract basis. This system is working well and is, Indeed, closely akin to methods adopted in this country.

One of the huge problems associated

with Fleet Air Arm planes is that of maintenance and, in some cases, as many as 60 per cent, spares are taken along, since carriers must go to sea as completely equipped as possible to do running repairs.

Undoubtedly, the most Interesting single feature of the Firefly is the modified Youngman flap. The Fairey Burracuda, described some few months back, utilised the flap in its original form. In the case of the Firefly, it has been modified somewhat, making it an even more useful adjunct to performance than previously.

In the Firefly it is possible to stow the flaps in a position under the trail- ing edge of the wing in such a manner that they lie flush with, and form part of. the underneath surface, when not required. The only addition struc- turally to secure this aerodynamic re- finement is the installation of a link- box on the wing's upper surface.

FLAP POSITIONS With the flaps lying flush and fonn-

ing part of the wing, the contour is almost as clean as that in a high- speed fighter. The take-off position for the flap Is at an angle of about 30 degrees to the datum line, and. in addition to raising the lift co-efficient in this position, it has a considerable slot effect, reducing the possibility of a stall during take-off. When cruising, or for long-range work, the flap is fully extended, but parallel to the wing, giving an increased wing area or, conversely, reduced wing loading.

When a landing is to be made, the flap is in its fully down position and thus bears a resemblance to the Fow- ler flao used on a number of Ameri- can aircraft. The actuation of the flaps is hydraulic, as are most services in the machine, and, although the two are not directly connected together, they are perfectly phased In operation.

The combination of an aerodynamically clean aeroplane powered with a Rolls Royce Griffon engine and these special Youngman flaps has resulted in the successful production of an aircraft which is extremely versatile in flight. With the flaps set in the cruising position, tire plane can flcat lazily along and make tight turns On the other hand, with flaps retracted, it takes on the qualities of a high- performance fighter and can climb "upstairs" at a really impressive rate.

Fuselage construction is of conventional monocoque style, except at the extreme tail, while a modified Warren- Girder system of tubular bracing is used. This system was adopted to minimise the possibility of breakage

The clean wing surface breaks up in surprising f a s h ion when the Firefly is folded up for storage in the hangar. The second sketch shows the 'earward position of the fin and rudder. (By courtesy of "The

Aeroplane").

■I

m

""t —_<2M! ,'L

/ / • r

•IS Mieai

PAGE TEN RADIO AND HOBBIES FOR JUNE, 1945

A V I A T I O tf

drawing I o( the Fail Firefly (or fhoje » like building i o I

Air ducts Immediately above the spinner on either side of the top cowling provide direct alr-ecoilng to the magnetos and generator. In the chin position are the coolant and oil system radiators, housed in a manner somewhat similar to the Typhoon and Tempest. Carburettor air intakes He along the lower engine cowling on either side and extend back to the leading edge of the wing. Hot air to provide cabin and gun heating respectively is taken from interchangers in the coolant system via lagged ducts. The use of a complete power egg assembly such as this reduces over- haul problems to absurdity, provided sufiicient spare "eggs" are available. The Griffon II- engine, as fitted to the Firefly, develops 2200 hp, is quite compact, has small frontal area, and feeds Its power to a three-bladed Rotol constant speed airscrew. Wing construction follows general metal-spar, rib, stringers and stressed skin practice. The plan form Is more or less elliptical, although not truly RADIO AND HOBBIES FOR JUNE,

such, in that the leading edge la straight. This Is the outstanding wing shape of the day, having been used on quite a number of top-line aircraft since first featured In the Spitfire, Wing folding, which is a necessity on carrier-borne aircraft, Is carried out manually, but Is accomplished In a lew seconds. The locking of the wings in place, however, is done hy- draullcally. Storage space for a Firefly with folded wings It. equivalent to a box of its own length and its height square in cross section. The ailerons and, in fact, all control surfaces with the ex- ception of the rudder (the rudder Is faBric-covered) are all metal. It ia interesting to note that the ailerons, which are pressed out In heavy-gauge sheet, ate so accurately made that' there Is virtually no de- tectable difference In aileron response from one aircraft to another—a most unusual feature. The undercarriage, which must have exceptional stability for carrier opera-

tion, has an extremely wide track and Is fully retractable. Each under-carriage leg retracts inwards and rear- wards. und is locked up by means of a lateh on the breaker strut This latch also serves to lock the gear securely In the down position, but Is assisted, in this Job. by a radius rod which governs the rearward retraction motion. The wheels are mounted on canti- lever axles and are prevented from twisting by spllnlng between the upper and lower oleo leg members. The tall wheel is also fully retractable, and is enclosed by small flap doors. Exten- sion and retraction of the undeTcarrla|e is accomplished hydrauHcally. This mechanism, together with all other hydraulic services on the aeroplane, Is produced by Lockheed. All the various devices which are a "must" for Fleet Air Arm aircraft are included, sueh aa catapult spools, wing folding, locking struts, and ar- (Continued on Xexl Pagel

PAGE ELEVEN

AVIATION

THESE PLANES ARE MAKING HISTORY

SpeedyuSAttack Craft

6 = DOUGLAS fl-26 - INVADER

NORIHAMLRICAN P51 -•MUSTANG-

Speed and firepower in aerodynamically-sound designs remain the touchstone of performance in modern warplanes. Mach- ines now rolling from American production lines have these

. qualities in full measure.

NEWEST US Army attack bomber is the versatile DoiiKlas A-2(i

Invader, said to be the speediest bomber ever built in the United States.

This "all-purpose'- machine, which incorporates all the experience gained by the US Air Force in low and medium level attack bombing, has offensive power which is adaptable to almost any combat situation; It has been designed to carry a very wide selection of bombs, fuel, cannon and machine-guns.

Announcing the A-26, a US War De- partment statement said that the plane was designed for either low or medium altitude operations against enemy aircraft on the ground, against tanks and troops on the march or in bivouac, towns harboring enemy troops, anti- aircraft emplacements, supply dumps and wharves, and naval vessels.

Versatility of the Invader, which has been in action since late last year, is indicated by the use of an "all-purpose" nose. This eliminates the necessity for taking the machine to the ■•modification centre" before going out to undertake some specialised task.

A high mid-wing monoplane, the A-26 is aerodynamically very clean. It embodies the latest laminar low-drag wing, sponsored by the National Ad- visory, Committee on Aeronautics.

Power comes from twin Pratt and Whitney Double Wasp engines of 2000 horsepower, which drive Hamilton Standard liydromatlc propellers. For additional control, the machine incorporates new style double-slotted "flaps

to reduce landing speed and assist take- off.

The A-26 has many features designed to simplify maintenance, and all parts are easily accessible. An inno- vation is the special engine mounting unit, which reduces the time needed for changing the motors. The new device weighs only 1001b.. but carries the 30001b, of the motor. It fits into the nacelle section of the wing and is at-

tached to the wing and engine at only- six points—six on the nacelle ring at the rear for the wing and six on the aluminium forward ring for the engine.

Heavily armed and armored, the A-26 is a nyuch more formidable plane than its older brother, the Douglas A-20 Havoc.

* * * Credited with a top speed of 450 miles

an hour, the P-51 Mustang (lower left) shares honors with the RAF's latest Spitfire, the Mark XIV., as the fastest propeller-driver aircraft.

Latest Mustangs, which are un- painted. have a ceiling of over 40.000 feet and a range of 2000 miles. The plane has tremendous hltting-power. In addition to the six .50-calibre machine-guns which earlier models carried. and two 5001b. bombs, the plane also has triple rocket-launchers under each wing.

MANY SUCCESSES Rocket-firing Mustangs have some

outstanding successes to their credit. As an example of this, it was recently revealed that, after firing 290 rounds of rockets in the China-Burma theatre. Mustangs had achieved the following results: 18 warehouses. 10 Japanese planes, four locomotives, one foundry, and two river boats destroyed; and two warehouses, five buildings, one locomo- tive and 13 Japanese planes damaged.

The Mustang is powered by a Pack- ard-built Rolls-Royce motor of more than 1500 horsepower, which drives a four-blade propeller.

The Mustang's transparent plastic "tear-drop" canopy provides remark- ably good visibility, both horizontally and vertically.

Overall length of the P-51 is 32 feet 3 inches, and wlngspan is 37 feet.

Planes of this general type are now in production in Australia. First built in the United States as a fighter for the R.A.F., the Mustang has proved a very successful attack aircraft since its adoption by the USAAF. #

TALONS FOR THE FLEET AIR ARM (Continued from Previous Page)

restor gear for stopping the aircraft after landing. All these things are housed in recesses, so that, in flying trim, the external surfaces are hardly broken.

Tire success of fleet fighter design is to pack into the aircraft this extra gear and plenty of armament and fuel, without sacrificing performance too much. Not only has this been done on the Firefly, but also compre-

Our Cover Picture WITH the *af in Europe at an end,

a proportion of Britain's ■rorlr- ers can be switched to t'o job of re- storing the home-front. The British Post Office plans a vast expansion of modern telephone facilities and, in our cover picture, an English girl is shown turning components for an automatic exchange.

»-

hensive radio and navigational equipment has been added, together with space for an observer.

The armament would appear to be quite adequate, as it consists of four forward-firing 20 mm Hispano cannons mounted two in each wing.

The new Firefly is by no means a small aircraft, having a wing span of 44ft 6in and a length of 37ft 7iin. General points of recognition are the elliptical wines, tailplane set well forward, and tall triangular fin and rudder assembly. The normal camouflage is sea-green and sea-grey on the upper surfaces and duck-egg green underneath.

Fireflies will no doubt add to the discomfiture of Nippon, as they flit around the flaming destruction which Is being wrought on Japanese-held bases and on her big cities.

They are of typically sound British design and construction, and must surely be the fastest single-engine two- seater fighter in existence today.

PAGE TWELVE RADIO AND HOBBIES FOR JUNE, 1945

FEATURE STORY

SCIENCE ON THE MARCH

TRUTH IN JEST A DEVICE developed at

Wright Field and known as the "Skyhook" is intended for dropping food, medicine and mail to isolated troops. It is stated to be superior to the parachute for this purpose, as in , ordinary wind it will land almost directly beneath its release point. The Skyhook resembles a lady's hat-box with a wing on the side, and is made variously in steel, aluminium and plastic with a capacity of 2i cub. ft.

* * * BRITISH TANK '[TIE latest British lank, the Comet,

led the advance across Germany after the Rhine crossing, it is officially stated.

It is Britain's fastest and most

MODERN WEAPONS 'IÎIE world's finest weapons, including

the heaviest and largest calibre artillery pieces, are being used by Aus- tralian forces on Tarakan. ,

The Australians' equipment includes every type of weapon which the Ameri- cans have used in the Pacific war.

They have an abundance of tanks, full and half-tack weapon-carriers, bulldozers, mobile cranes, jeeps, and other motor vehicles.

In addition to warships, every type of craft, from tank-landing ships to

LATEST weapon used by the Japanese In the OVinawa campaign is a piloted, roclet-propellod bomb, launched from a long-range bomber. The Americans

call the new weapon a "Baka." The bombs are built on the sleek lines of a miniature aircraft. They are

greenish grey in color and bear the emblem of the Kamikaze (Suicide Corps). The bomb carries a heavy charge in the nose. It has no propeller and no undercarriage.

Because of the abnormally high wing loading—the wing span is only 16 feet—the rockets must propel the plane at an enormous speed before if can be manoeuvred. The "bombs" are 19 feet long. These one-way suicide machines, constructed of three-ply and light metals, have not been used in groat numbers.

There has been no announcement of the range of the bomb, but when carried by a long-range bomber it should have a radius of action of more than 2000 miles. .

heavily armored cruiser tank. De- veloped from the Cromwell, it has a Rolls Royce Meteor engine and a 71mm. gun, with new gun-laying devices which make it the most accurate tank gun in the British Army. No Comets fell into enemy hands.

* * * MIDGET FIGHTER I JELL Aircraft Corporation are experi-

meriting with a tiny all-wood fighter plane designated as XP-77. It is of conventional single-engine single- place design, and has a tricycle undercarriage. , Very high speed and manoeuvrability are claimed. Bell are also producing the world's largest combat plane, the B-29 Superfortress.

* ★ ★ MINIATURE RECORDER

A RECORDING set the size of a folding camera, completely built-

in save for a microphone on the cord, has been developed by a Chicago inventor. Powered bv a battery receiver and destined for postwar civilian use. it weighs only three pounds. It picks up anything the human ear can hear. Radio and newspaper reporters are the most likely users of this midget set.

* * *

RADIO IN U.S. 'P. A. M. CRAVEN, former P.C.C.

commissioner, has advocated that the band 60-100 mcs should be reserved for F.M. activities. He estimates a demand for 2000 commercial stations and as many educational transmitters for F.M. during the next 10 to 15 years. A proposal from J. L. Weiner is for three non-advertising programmes at one end of the dial. A special superimposed squeal would render the programmes useless for all except those who rented a special filter—thus pay- ing for the service. It is suggested that 70.000 Americans will be eligible to operate "Ham" transmitters.

mechanised, collapsible boats, took part in the Invasion.

* ★ * STEEL CLOTHING yTAINLESS steel wire as fine as

hosiery yarns are in production by some steel companies, according to Mr. Walter S. Tower, president of the American Iron and Steel Institute.

RECORD DIVE \ RECORD deep-sea diving depth of

550 feet was established in a diving lank by Jack Browne, 28, a civilian diver.

Previous record of 500 feet was set by a Navy diver in 1938.

Browne" made his test dive in a tank at Milwaukee containing eight feet of water, under pressure of 244.761b. to the square inch.

Throughout the dive he spoke by telephone with naval observers and a doctor.

* * *

BLOOD PUMP 'pHE invention of Dr. Julian Smith,

a well-known Melbourne doctor, enabling a blood transfusion to be given at a much faster rate than is

ossible by the ordinary drip method, as saved a number of lives on

Tarakan. Normally a transfusion of 1000 ccs.

of blood—about a pint and a half- may take from three-quarters of an hour to an hour and a half, depending on the condition of the wounded man. With the rotary pressure pump invented by Dr. Smith it can be given in 10 minutes.

On Tarakan the pump is being used by a young Sydney doctor who first saw the pump used by Dr. Smith's son, who is also an Army doctor. He bought one at his own expense.

When the field ambulance was working at high pressure, dealing with wounded from the fierce action fought round the airstrip, quick transfusion given by the pump saved the lives of several men who had been badly hit.

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RADIO AND HOBBIES FOR JUNE, 1945 PAGE THIRTEEN

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PAGE FOURTEEN RADIO AND HOBBIES FOR JUNE, 1945

RADIO THEORY

raEVBli IN THEOBY & PRACTICE

Part 2.—Electronic Systems

In our last issue, we outlined the technical basis of television and went on to explain the workings of the simple types of mechanical television equipment. This month, our discussion centres around the application of purely electronic devices to the transmission and reception of picture images.

By W. N. Williams

Although it is duncuit to be too definite at this early stage,

it seems likely that electronic television will predominate for domestic equipment, with mechanical equipment finding application in large-screen systems for public entertainment.

For those who may have missed the previous Issue, the operation of any television system hinges on a system of scanning, whereby the scene or image to be televised is broken up Into a series of lines of varying light and shade. The tones in each line are converted into appropriate electrical signals, which are superimposed on a carrier wave and transmitted in the normal fashion.

At the receiving end, the Impulses are utilised to impart corresponding properties of light and shade to locally generated lines of light. These lines are made to appear on a viewing screen, or in a viewing window, in exact sympathy with those derived at the transmitting end.

As a result, the whole image is re- constructed. The process of scanning is continuous and the picture is "generated" many times each second, so that the viewer is not conscious of undue flicker effect. It is quite im- material whether the subject televised is still or in movement;

A pre-war Briiiih tele- viiion receiver, marketed by the Ferranti Com- pany for about 70 gns. The picture ij viewed directly on the screen o( the C.R. Tube and is 11 in. x 9in. overall. The ultimate size of a direct viewing screen is limited by manufacturing difficulties and atmospheric pressure on the

glass.

cal systems In the competitive postwar market. The heart of electronic television is

the cathode-ray tube in one or other of its various forms. Small cathode- ray tubes are more or less common in laboratory test gear, and the more technical readers will be conversant

projecting it towards the screen at the end of the tube.

The electrodes H. P and A are often referred to as the electron "gun" and. by carefully controlling the applied

(b)

(a)

the process goes on just the same, the receiver building up from In- stant to Instant just what before the "camera."

In the search for clearer Images, there has been a progressive decrease in the width of the scanning line, and therefore an increase in the number of lines comprising each complete picture. Progressively higher scanning

Figure I. Illusfrating fhe elecirodo arrangement in typical cathode-ray tubes, usin^ electrostatic deflection (above) and (on fhe lelt) electromagnetic deflection. Both types of tube are used in television receivers. Most tubes are evacuated bul a few contain a small quantity of gas.

speeds (more frames per second) have also been adopted, so that the simple Nlpkow scanning disc has had to give place to far more refined and com- plicated mechanical devices.

The resulting need for close manufacturing tolerances and high operating speeds, together with problems of maintenance and mechanical noise, arc all likely to prejudice the chances of mechani-

wlth the principles Involved. - Typical cathode-ray tubes are illustrated in figure 1.

A cathode <K) produces free electrons, which are guided by a system of metallic tubes and vanes in the general direction of the screen (S). The electrode G is normally maintained at a negative potential and serves to control the number of electrons which actually leave the cathode enclosure. In this respect it acts as a control grid.

The electrodes H. F and A are maintained at progressively higher positive potentials with respect to cathode, and are so arranged that they consolidate the random stream of free electrons into a definite beam,

voltages, it Is possible so to focus the beam of electrons that it strikes the screen at a single spot of quite small area.

The screen is actually a whitish chemical deposit on the inside of the glass envelope, which has the property of glowing brightly wherever the beam of electrons happens to strike It. It is therefore the essential link between a purely electrical phenomenon and something visible to the eye.

As the electron beam leaves the gun. it is very sensitive to electrostatic and electromagnetic fields, and this fact is put to good use In the tube.

In figure la two sets of deflector plates are shown (B and C) which are brought out to external terminal


RADIO AND HOBBIES FOR JUNE, 1945 PAGE FIFTEEN

RADIO

ELECTRONIC TELEVISION

lugs. Initially these metal plates have little or no Influence on the electron beam, which passes between them and is substantially unafiected by their presence.

' However, if a positive voltage is applied to one particular plate, it will have an attraction for the electrons in the beam. Their velocity is such that they are not arrested, but the beam as a whole is bent towards the positive deflector plate.

The spot of light on the fluorescent screen therefore appears to one side of its normal centre position, depending on the direction and the amount

ertia, Therefore, the direction of the beam can be varied at any desired rate, and likewise its intensity, There are no, mechanical stresses and no moving parts. Little wonder that the system has so much appeal to radio engineers!

★ ★ ★ Before proceeding further with our

examination of the cathode-ray principle, it is necessary to switch our minds to another basic requirement of a television system, namely a means whereby scanning can be accomplished at both transmitter and receiver.

With mechanical systems, it is accomplished bv directing a spot of light through a series of whirling discs or by some other similar arrangement. With

Figure 2. By application of an altarn- ating veltaga to tha raipactiva pairs of deflactor plates, the light spot may be made to produce a vertical or a hori-

zontal lina of light.

by which the electron beam has been deflected. The deflection is further increased if the opposite plate is made negative with respect to cathode, since it exercises a repulsive influence on the electron stream.

By suitably mounting the tube, the two plates may be utilised to move the spot of light, say, in a vertical plane. The amount of deflection up or down depends entirely on the magnitude and the polarity of the voltage applied to the deflector plates.

If an alternating voltage is applied between the deflector plates, the spot will move up and down with the frequency of the alternations and, if the frequency exceeds a few cycles per second, the moving spot will be seen as a single line of light.

The second pair of deflector plates are at right angles to those just mentioned, so that the application of a voltage between them will cause the beam and the spot to be deflected in a horizontal plane.

The simultaneous application of voltages to both sets of deflector plates may move the spot into any corner of the screen, and may result in the production of a wide variety of patterns, so familiar to all who have used the cathode-ray oscillograph.

MAGNETIC DEFLECTION Precisely the same general effects can

be obtained magnetically by replacing the electrostatic deflector plates with deflector coils placed in proximity to the neck of the tube. This is referfed to as electro-magnetic deflection.

There are advantages for both systems and some tubes even employ a combination of deflector plates and deflector coils to produce the desired results.

Here then Is the basis of electronic television. An assembly of electrodes which will produce a fine line or beam of electrons, and a means whereby the beam can be diverted or bent, within limitations. In any desired direction. The subjects of the action are tiny

electrons which, for this purpose, may be regarded as having no mass or in-

cathode-ray equipment, scanning has to be accomplished by bending the electronic beam electrostatically or magnetically, so that the spot traces out exactly the required path.

It is, therefore, necessary to provide a control voltage or current of exactly the right nature and frequency. Let us revert to the elementary discussion on page 15 of our last issue.

Assume that, at a particular instant the electron beam is so deflected that the light spot is impinging on the bottom left-hand corner of the screen. We

Figure 3. A sawtoo+h voltage as used to deflect the electron beam at both

transmitter and receiver.

Thinking in terms of control, we need a voltage or current which will change gradually and at a uniform rate for a definite period of time, then suddenly revert to its original value, before commencing another cycle.

Plotting voltage against time, we have the waveform depicted in figure 3, which is referred to in technical parlance as a "sawtooth" wave. For purposes of beam deflection, two

distinct sawtooth waves are seen to be necessary, one to move the beam up and down and a lower frequency wave to move it bodily sideways. Alternatively, if the scanning is performed in a horizontal plane, the higher frequency sawtooth will perform this service, and the lower frequency will provide the necessary up and down movement.

In actual fact, this horizontal scanning has been adopted as standard by most authorities.

SCANNING METHODS In simple progressive scanning, the

beam commences near the top left of the picture and moves at an even rate to the right hand extreme. It then flicks back to the left extreme and moves to the right again, but immediately beneath the first trace. This process (illustrated in figure 4) con- tinues until the whole of the screen area has been covered, after which the beam flicks back to its starting point for the next cycle.

A method which produces less flicker is known as Interlaced scanning. The beam traces out a path corresponding to the first, third, fifth and all odd lines, then flicks back and traces out the even lines. The actual path traversed by the spot is illustrated in figure 5. Interlaced scanning naturally requires special provision in the sweep circuits.

The number of lines into which the picture area is to be divided is the subject of much discussion at the moment. A large number of lines greatly improves detail, but increases

Figure 4. Illustrating the path traced by the beam in simple progressive scanning. The specing between lines is much

exaggerated (or purposes of clarity. mention the word "screen," but only for the purpose of clarity; try to think rather in terms of the electron beam and its deflection.

With the beam diverted towards the bottom left-hand corner, we may desire the spot to move vertically upwards along the left-hand side of' the screen at a uniform rate. The moment it reaches the upper extreme of its travel it must suddenly be returned to the bottom of the screen, ready for another upward trace.

At the same time, the beam must be shifted slightly to the right, so tha' the second trace will be exactly along, side the first. This process will con tinue until the whole picture area har been covered, after which the bean must be returned instantaneously to it- starting point, to scan the picture all over again.

To acconjnlish this, we need two distinct controlling voltages of a ven special nature. Think first of the vertical beam deflection. The beam mus be deflected vertically upwards at ar even rate, then suddenly switched back to the bottom edge of the picture area

Figure 5. With Interlaced scanning, lines ere scanned alternately. Picture frequency Is effectively doubled without increasing frequency requirements for transmission.

the difficulties of transmission and reception.

The existing R.M.A. standard, which is of a temporary nature, •ipecifies 441 lines and a frame frequency of 30 per second. It allows for interlaced scanning, which therefore means that the general outlines of the picture are built up 60 times per second. The vertical sweep oscillator must

herefore produce a sawtooth wave ,vlth a frequency of 60 cycles per ;econd, and the horizontal oscillator a frequency of 30 x 441 equals 13.230 c/s.

The whole subject of sawtooth oscillators is far too broad to permit dls-

PASE SIXTEEN RADIO AND HOBBIES FOR JUNE, 1945

RADIO THEORY

cussion in this article, but those who have studied the operation of the cathode-ray oscillograph will have some understanding of the circuit arrangements necessary.

It is possible to obtain sawtooth voltages with the aid of gaseous dis- charge tubes, with special oscillatory circuits, or by specially "shaping" the output from a conventional sine-wave generator. ,

Whatever method-is used, however, it must lend itself to the application

Light Sensitive Surface

Slect-

r on G-un

Supply Voltages "

Figure A. The Iconoscope and the method by ^which it converts light images into

electrical signals.

of synchronising voltages, to keep the scanning circuits at transmitter %nd receiver exactly in step.

The usual idea is to adjust the sawtooth generator so that its natural oscillatory period is slightly longer than the accepted standard. The special synchronising pulse is then utilised to "trigger" the circuit into operation at the commencement of each cycle.

Modern practice is to provide a syn-

derived at the transmitter by mechanical means.

First, let us think of the transmitter. The modern television camera and

studio bears no resemblance to the booths used for early television trans- missions. The stage is not unlike a miniature "movie" set, while the television camera itself bears striking resemblance to its photographic counter- part. It contains only the apparatus essential to convert light images to electrical impulses, being connected to

amplifying and supply e equipment by means of ace long, flexible cables.

Heart of most television cameras is the so-called "Iconoscope," invented by Dr. Zworykin and developed by RCA (America). The operation is illustrated in

figure 6. T The tube contains an u electron "gun" which is

amplifier essentially similar to that already described in connection with figure 1. This

—assembly produces a beam of electrons which can be controlled by means already described. Its "tar-

get," however, is a metal plate whose surface is treated so as to make it light-sensitive.

To the surface of the plate is first cemented a thin film of high grade mica. On this is deposited countless tiny particles of silver, which are then covered with a thin film of ceasium oxide. There is naturally a capacitance between each tiny silver particle and the back plate, so that they form, in effect, countless small condensers, with the metal sheet as a common plate.

In use, the image or scene to be televised is focused by ordinary optical methods on to the treated surface. The

Figure 7. Showing how the iconoscope is arranged In a \V ^ complete television camera. The two \ lens syslems are mechanically coupled, the upper one serving as a viewfinder tor the operator. Note the signal lights and the earphones. A. is the mosaic screen; B, electron gun; C, electron beam: D, deflecting coils; E and F, electrical

output connections.

chronising pulse at the beginning of each horizontal sweep and a special and longer pulse at the beginning of each frame.

With these facts in mind, we can now go on to examine the actual application to television transmission and reception by purely electronic means.

However, do not be confused into believing that electronic and mechanical television have nothing in common. Television signals derived by electronic means can be "tuned" on a mechanical receiver, provided both are designed to operate to the same standards. In just the same way, it would be feasible to reproduce electronically the signals

LI I E C ilWI

Courttuy A HC

ceasium-silver combination produces a photo-electric effect, and each small unit loses electrons, which flow to the positively charged shield within the Lube. Thus each tiny condenser becomes positively charged to a greater or lesser degree, depending on the amount of light which happens to be falling on it.

When the electron beam begins to traverse the mosaic plate, in the ordinary process of scanning, it impinges at some instant on each of the tiny charged condensers. Immediately each condenser is affected its charge is neutralised and a minute impulse is im-


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RADIO AND HOBBIES FOR JUNE, I9H5 PAGE SEVENTEEN

RADIO THEORY

TEST

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parted to the common back plate. As the electron beam goes on its way, the tiny condenser immediately builds up a fresh charge and is ready for the nejit scanning cycle.

The tiny impulses are being received ail the time by the common back plate, and the resultant signals are ampli- fied and transmitted in the usual way.

In practice, several Iconoscopes may be in use simultaneously, and the signals brought to a common control panel. Here the producer selects the distant, angle and close-up shots as he requires, and feeds the appropriate signal to the transmitter by the simple process of electrical fading and mixing.

Another RCA television camera tube is the "Orthicon," which boasts high sensitivity and is therefore suitabldl for televising outdoor events.

ffTTTrV Figure 8. A typical modulated television carrier, In which the peaks represent dark areas and the troughs bright areas. Note the prominent

rectangular synchronising pulses^

A third and distinctive type of pickup tube is the "Image Disec- tor." In this, the scene to be tele- Vised is focused optically on to a translucent light-sensitive plate, which emits electrons from its rear surface in direct proportion and density to the light values composing the Image. By magnetic means, the electrons are

Induced to travel in straight lines to a second smaller plate, located some distance behind the first. Actually, if the second plate were coated with a fluorescent material, a small image would appear on it.

However, this is not the purpose of the device. In the centre of the second plate is a small' hole, through which some of the electrons can proceed to a rear collector plate.

In operation, an external magnetic field is employed to swing the whole electron image back and forth and up and down, so that every point in it passes across the aperture in the second plate.

The number of electrons passing through the aperture varies from one instant to the next, according to the degree of ilium illation of the corresponding portion of the cathode. It only remains to collect the electrons in question and pass on the signal currents they initiate for further amplification. " Before proceeding to a discussion of

Figure 9. Prob- [r - speaker^ able layout of 1 f T ^ ^ table model re- ' I ceivers, utilising | |

. a small tube and j | direct viewing of i |

' the screen, I I

K— ^ I ,^Tu b I L

Chassis '!•

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receivers, one point is worthy of special mention

It is very difficult, if not impossible, to obtain electronically a perfect sawtooth scanning voltage (figure 3), the steeper side of the wave tending to he slightly off true vertical. This means that the return of beam from right to left,

PAGE EIGHTEEN RADIO AND HOBBIES FOR JUNE, 1945

or from bottom to top of the picture Is not Instantaneous, but occupies a definite amount of time. At the transmitting end it may

therefore generate unwanted impulses as it flicks back across the plate, and, at the receiver, it may leave a wavering and indefinite trace "across the face of the picture.

This undesirable effect is countered by arranging the circuit at the transmitter so that, during the instant the trace is returning across the screen, an impulse is sent representing "blacker than black." The special impulse blots out the return trace, and also serves as a synchronising pulse for the sawtooth oscillators.

AT THE RECEIVER From earlier discussion, it should not

be difficult to understand just what goes on at the receiving end. The source of the image Is a cathode-ray tube along the lines described in connection with figure 1.

This is provided with the necessary power supply, which usually involves provision of a thousand or more volts d-c, at a current of a few mllliamps. Also there are the sawtooth oscillators necessary to produce the scanning effect with the electron beam.

The tube is usually viewed in semi- darkness, so that the whiteish screen is seen initially as no more than a dull grey shadow. When the electron beam causes the screen to fluoresce, it naturally stands out quite brightly.

In the absence of any picture signal, the sawtooth oscillators sweep the spot rapidly over the picture area, so that the screen is—or should be—Illuminated in an even fashion over a rectangular area.

We have already learned, however, that the control electrode in the gun of a cathode-ray tube can vary the density of electrons in the beam, and therefore the brightness of the spot which it causes on the screen of the cathode-ray tube.

To utilise this effect, the picture signals from the television transmitter are fed to the control electrode In such a way that the brilliance of the spot is made to vary from one instant to the next, as it travels aoross the screen.

Dark areas In the original televised scene produce signal Impulses which cause a momentary dimming of the flying spot on the cathode-ray screen in the receiver. Bright areas have just the opposite effect.

PICTURE BUILT UP The synchronising pulses already

mentioned keep the receiver exactly in step, so that an image of the original scene is built up on the fluorescent screen of the tube. Electrical controls on the receiver permit variation of the overall intensity of the picture and sundry other adjustments are possible.

The exact nature of the coating on the cathode-ray tube screen determines the tint of the final picture. Some screens have a definite green tint, others blue. The general objective is to make the trace as nearly white as possible in order to produce a black- and-white picture. The density of the black areas depends largely on the amount of light reaching the screen, and therefore on the general level of light in the viewing room.

By varying the nature of the fluorescent coating, it is possible to control the persistence of the cathode- ray screen, or the period of time dur-

, in? which a given Impulse remains visible. This general effect can supplement normal persistence of vision, but

Figure 10. A popular layout in console receivers utilises a large vertically- m o u n ted C.R. Tube and a mirror beneath the

tilted lid.

SMirror

\ / 1 1 1 I Cheesia' I | I i I i L ' it naturally 1 I i 1

cannot be car- ' ] 1 ried too far. ,

The ratio of , x--/ t width to ( Sp„k9rl i i height in a i t-_j 1

television pic- 1 si] ture has been ! standardised to ' \ , conform to present motion picturfe practice. How- ever, with a cathode-ray tube, the overall dimensions are limited bv the diameter of tlje screen.

With tube screens up to five or six Inches in diameter, manufacturing technique is now commonplace, but, beyond that, the problem of air pressure becomes increasingly important. Since the tube is evacuated internally, the glass wall has to withstand a pressure of 151b. for every square inch of its surface area.

The tube must be made strong enough to withstand the initial pressure, and also to minimise the chances of "a violent and perhaps dangerous end, if the glass is inadvertently bumped. The whole physical size of the tube is increased, as also are the operating volt- jiges required and the difficulties of

RECEIVER — CHASSIS

Figure II. A projection lystem proposed by RCA, utilising a high intensity tube, a special lens and a frosted viewing screen set into the front of

the cabinet.

maintaining accurate focusing over the whole screen area.

At this early stage, one can only speculate as to the form which television receivers will take in the immediate postwar period.

There is likely to' be a certain call for small table-model receivers, which will probably use from five to nine-inch tubes, with the screens viewed directly through a rectangular window

Tubes ni"e inches and upwards in diameter will probably be used in con-

RADIO THEORY Sole receivers, and a popular arrangement has been to mount the tube vertically, in the interests of safety and economy in space, A mirror beneath the tilted lid allows the image to be viewed from the normal sitting position in front of the cabinet.

In the interests of tube life, the brilliance of the image on the cathode- ray screen has to be limited. It is quite satisfactory for ordinary viewing, but does not lend itself to indirect projection or to magnification by conventional optical systems. These factors have hitherto hindered the development of domestic systems involving the projection of an electronically derived image on to a viewing screen.

However, fairly recent work by RCA - America holds much promise in this direction. It centres around a high intensity tube developed by RCA, a new type of lens system evolved by a German, Bernhard Schmidt, and the use of clear moulded plastic for optical work, in place of ground glass lenses.

According to one report, the overall result of the combination is a Pro- jected television image 7J times brighter than had previously been possible. The following is a brief description of the RCA development, as illustrated in figure 11. Wfi quote:

MIRROR AND LENS "The svstem includes a spherical

front surface mirror and an aspherical lens. The mirror—shown at A in the drawing—reminds one of those used in giant astronomical telescopes.

"The special lens Is at B, One side is flat, the other rises slightly at the centre and at the edges, but is de- pressed in the intermediate area. In optical language, the surface contour renders the lens optically positive in the centre, with a gradual change to negative in the outer portion^.

"The television tube, C, Is inserted through an opening in the centre of the lens. It projects its image to the mirror, which reflects it back through the aspherical lens to the plane mirror, D and on to the screen, as shown by the dotted lines. The lens corrects aspherical aberration produced by the mirror and focusses the image.

"The great light-gathering power of this system results in a much brighter image for any given amount of enlarge- ment, as compared with older projection systems. .,

"Probably, most interesting to the prospective televiewer is the news that the lens—which might be prohibitively expensive if ground from a glass blank in the ordinary manner—is moulded from a clear plastic -'material. This comparatively inexpensive proems says pr;a. will make it possible to nse the system in medium-priced home television receivers"

Although we have devoted two full articles to the subject of television, a great deal has been left unsaid. Little or no reference has been made, for ex a mole, to color and stereoscopic images, large screen projection, receiver design. &c. , u _ ^

However, the reader should how have a fsirlv clear picture of just how television is achieved, and these additional aspects will be covered in turn as space permits.

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radio and hobbies for june. 1945 PAGE NINETEEN

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PAGE TWENTY RADIO AND HOBBIES FOR JUNE, 1945

RADIO THEORY

jflP RADIO SET \S WELL HQEDl

Through the good offices of one of our younger readers, Mr. Benno Seppelt, we were recently afforded opportunity to have a good look at a radio set from a Japanese plane abandoned at Hollandia. After examining the equipment it was necessary to revise certain preconceived notions about Jap. goods.

IN the early stages of the Pacific war considerable nnhlicitv was I war considerable publicity was

given to the rather outmoded design of Japanese radio equipment and to the makeshift nature of the components used.

Some such articles were well found- ed, as also were statements that the Japanese, like ourselves, did not fully appreciate the need for tropic-proofing equipment destined for use in equator- ial regions.

However, the set which reached our workroom bore eloquent testimony to the fact that the radio experts of Nip- pon have not been slow to learn the lessons of the Pacific war. Although intended for aircraft use, the set appeared to be well protected by wax and varnish against possible damage from humidity effects and fungoid growth.

The Japanese characters, and the compact layout rather deterred us from trying to discover the exact circuit arrangement, it was notable, however that all six valves were an exact Jap- anese copy of the American 6F7. Act-

0

ually the American and the Japanese type numbers were branded on opposite sides of the glass envelope.

Although the 6P7 is quite an old valve, it is nevertheless true that many modern types are similar electrically, the main differences being largely physical.

Furthermore, experience seems to in- dicate that the most reliable military receivers are often those with several low gain stages, as opposed to receivers using fewer valves, but a higher figure of gain per stage.

A further and quite an obvious advantage of this standardisation is the way it simplifies the valve replacement problem. In some cases it might even be possible to restore a receiver to par- tial operation by interchanging two valves so that the faulty one is placed

The timing dial is a spring- ' loaded double-worm arrrangement which gives very fine tuning, with a complete freedom from back- lash. An interesting point Is that the reference hair-line for the dial scale can be adjusted over a small range, apparently for cali-

bration purposes, fc. The wiring is car-

ried out with what appears to be spaghetti _ covered multi-strand wire, and there is also an

| what smaller " than

i Wire-wound and W carbon resistors are

i of standardised pat- Smirt ■ tern and each indi-

; vidual resistor is kaHT fixed upright be-

neath the chassis by PPPlaPlSpsS means of bakelite ,0^ spacers at each end,

and a brass mounting bolt through its centre. The resistor lugs, therefore, form rigid terminal points

for the wiring, and for the numerous ceramic-cased mica condensers.

Plugs are provided for the connection of the external power supply and immediately above them is a panel marked with a variety of operating voltages. A number of multiplier and shunt resistors are connected to this panel, which suggests that the necessary checking could be carried out with some form of standardised meter movement.

The whole receiver slides easily into a light metal case, which is shock- mounted within the aircraft.

Prom the same source we obtained for inspection the bombsight pictured on this page.

It is fixed to the side of the bomb aimer's eompartment by means of the

face plate In the foreground, and manipulation of the two-in-one handle immediately above the face plate permits the bomb aimer to keep the sight level during the bombing run. The level position is Indicated by a small

in a socket where its short-comings may be of lesser importance.

From a purely mechanical viewpoint the set is one of the nicest we have seen for many a day. It is built around | a die-cast, but otherwise conventional * chassis, to which is attached a front panel, and a system of chromium- plated brackets building its outline up to a rectangular box shape. Panel size is 9jin. x 6in., and over-all depth about eight inches.

The main tuning coils are built into a long narrow metal drawer with a series of studs along the bottom, making contact with fixed phosphor-bronze leaves. The coil box in the receiver is marked 2,5 to 5 megacycles and other bands can apparently be covered ^ by pushing in the appropriate coil ARM box. mSM

bubble-glass, seen in the extreme top centre of the picture.

Contained within the body of the sight is a small lamp and optical system, which projects several fine lines of light on to the rectangular viewing glass.

This glass is slightly discolored, so that the bomb aimer can see the inter- secting lines by reflection in the glass, and, at the same time, view the ground through the glass as it passes beneath the nose of the bomber. When the lines of light and the objective coincide, the bombs are released.

A course and a vernier control make possible corrections for drift, while al- lowance is made for height and speed by tilting the viewing glass. The figures on these various adjustments suggest that the bombsight is intended for use in conjunction with conversion tables or possibly a separate computing device.

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RADIO AND HOBBIES FOR JUNE, 1945 PAGE TWENTY-ONE

RADIO T H EORY

PROBLEMS OF SOUND REPRODUCTION

Previous articles in this series have dealt with the necessity for adequate frequency range in the design of equipment for high quality sound reproduction. We continue now with a discussion of various other contributory factors. First, of all,

noise level.

ARTICLE 3 ■Conclusion

NOTHING is more ruinous to otherwise high quality repro-

duction than a background of hum, hiss and crackle. While all can be due to transmission limitations, the first at least is more than likely due to faulty design at the receiving end.

Its presence Is likely to be far more noticeable in a high-quality sound system than in equipment of mediocre design. In the latter case, the restricted low frequency response may actually reduce the degree of noticeable hum in the output.

Hum may be introduced either directly by the power supply, due to insufficient filtering, or it may find its way Into the grid fclrcuit of initial stages of an amplfier. With 50-cycle mains and full-wave rectification, the hum frequency will, in the first case, be 100 cycles per second, and, in the second case, 50 cycles per second, with a liberal admixture of harmonics.

The cure for filter hum is obvious. High fidelity standards demand a high tension filter having at least two stages, and thorough decoupling of all low- level plate and screen grid circuits.

Induced hum presents a more serious problem, because of the number of ways in which it may be introduced.

Any conductor or component hand- ling an alternating current is sur- rounded by a continually varying magnetic field. If another conductor is brought sufficiently close to the magnetic field, a voltage will be developed in it.

Such voltage may be quite large if the particular component happens to be an inductor of one type or another. Audio-frequency transformers or chokes should, therefore, not be mounted in close proximity to power transformers and filter chokes.

SEPARATE POWER SUPPLY The power supply should preferably

be constructed on an entirely separate chassis to that occupied by the amplifier or, at least, to that occupied by the low-level or preliminary stages. It is not considered bad practice to place the output stage on the same chassis as the power supply.

Obviously the magnitude of the hum problem is greater if one is designing for high overall gain.

Complete isolation of power supply and amplifier also obviates the possibility of modulating the electron stream in one or more of the valves by the field surrounding the power transformer, choke or speaker field. Elec- tromagnetic coupling via the metal chassis is also overcome.

The adoption of Indiscriminate shielding of all input leads to high Impedance circuits as a preventive measure against hum is ill-advised and seldom fully effective. Some shielding is desirable, certainly, but, carried to

excess, this practice shunts the respective grid circuits with a comparatively large capacitance. As a consequence, attenuation of high notes may result.

It is far better to attack the trouble at Its source and to aim at complete isolation between the power supply and the low-level amplifying stages.

* * * Harmonic distortion simply means

that, in the output of a reproducer, there is not the same relationship between the fundamental note and the harmonics as existed in the original sound. This form of distortion is often more distressing in equipment having wide frequency range than when the range is restricted. This statement will, perhaps, be clearer if we quote actual figures.

Assume that, with a particular amplifier, third harmonic distortion exceeds a tolerable limit at frequencies above 2000 cycles per second. The third harmonic of 2000 cycles per second is 6000 cps, so that, if the output from the loud-speaker drops sharply beyond 4500 c/s, the third harmonic distortion will not be very apparent.

If, on the other hand, the amplifier has a wide range (say to 12,000 cycles per second) then third harmonic distortion of all fundamental frequencies up to 4000 cps will be reproduced at full efficiency.

Harmon 1 c distort 1 o n may be reduced by making sure, for example, that power output stages are operated with correct load Impedance: further, that voltage amplifiers are operated under such conditions that, with correct value of grid bias, the signal applied to the grid circuit never moves on the straight part of the grid voltage plate current characteristic, or beyond zero bias. The application of negative feedback with pentode or tetrode output valves is also a valuable aid.

* * * Reproduction of transients Is an im-

portant characteristic. Transients are produced by sudden non-periodic air disturbances, such as by a slammed door, firearms, percussion type musical instruments (drums, cymbals, &c.). The piano also creates such an effect at the moment of percussion between hammer and strings.

The effect of transient sounds on the auditory nerves is one of shock rather than a consciousness of pitch, as is produced by a sustained musical note

An analysis of any transient sound Indicates that it comprises a numbei of periodic waves covering the frequency range from zero to Infinity.

In this respect, they are analogour to atmospheric electrical disturbances

i

1

j

or "static," which have the same effect on the aerial of a radio receiver.

A common form of transient distortion produces an effect of "haqg over"' following percussion sounds, tor the realistic reproduction of transients, the equipment must have the widest possible frequency range, and the dia- phragm of the reproducer should come to rest immediately the motive force is removed, so that the characteristic staccato nature of the sound will not be blurred.

"Hang-over" is often due to insufficient damping of the loud-speaker movement. Damping is effected both mechanically through the cone suspension and electrically through the load imposed by the plate resistance of the power output valve.

DAMPING ON CONE The mechanical damping introduced

bv the cone suspension must be a com- promise with sensitivity. For complete control we have, consequently, to rely also on the electrical damping due to the plate resistance of the output stage.

Because of their lower plate resistance triodes have a greater natural damping factor than either pentodes or tetrodes. Broadly speaking, therefore, reproduction of transient sounds will be better when a triode output stage is employed. However the application of negative voltage feed-back to pentodes and tetrodes improves their damping factor to such an extent that it may be made equal to or better than that of a triode.

* * * Scale distortion is psychological

rather than electrical. One of the peculiarities of the human auditory

system is its varying sensitivity to extreme high or low frequencies. 1 f the equipment is oper-

ated at an unnatura 11 y high or low

level, the relationship of the bass and treble end of the scale to the middle frequencies will not be the same as in the original sound.

Scale distortion is a rather contro- versial subject. Some accept it as a natural effect. Others insist upon tone compensation which can be so adjusted that, throughout the complete volume range of the equipment, the apparent acoustic output possesses a straight line frequency characteristic.

* * * Cross modulation applied to audio

frequency sound systems may be especially noticeable when a single speaker is employed to handle the output of the amplifier. Under such circumstances, and when the equipment is operated at high level, bass notes of large amplitude are likely to modu- late treble notes, due to spurious par- tial vibrations set up in the cone.

The most effective way of dealing with the trouble is to use at least two speakers—one for low and middle frequencies, and the other for high notes.

★ ★ ★ Adaquate power output Is essential

(or high quality reproduction. The

By L. B. Graham (Principal of the

Australian Radio College)

RASE TWENTY-TWO RADIO AND HOBBIES FOR JUNE, 1945

maximum power output of the equipment will of course be largely dictated by the size of the area to be served.

The need for sufficient reserve of power will be illustrated if we assume a typical case. Assume that an amplifier has a maximum undistorted power output of 5 watts, and that it is being used in a room of such dimensions that, with a solo instrument in a reproduced orchestra playing softly., its power output has to be 60 milliwatts.

Now if a sudden loud passage by the full orchestra occurs, such that the required power output is 100 times the previous figure, the amplifier will be called upon to deliver 6 watts, which is one watt greater than Its maximum undistorted output. The result is inevitably severe distortion. The remedy is obvious.

DYNAMIC RANGE Dynamic range or volume range

refers to the ratio between the softest sound and the loudest sound likely to be reproduced. The dynamic range encompassed by a large symphony orchestra is about 1,000,000 to 1, which represents a range of 60 decibels.

The provision of adequate dynamic range is governed by the available undistorted power output and the resi- dual noise level of the amplifier and associate equipment. Obviously the softest sound which we can reproduce is limited by the noise level, because the reproduced sound must at all times be sufficiently greater than the noise level to be intelligible.

It is also obvious that, if the amplifier has limited power output, the contrast between soft notes and loud notes must also be limited, because there will be Insufficient reserve of power to deal with sudden peaks, or sudden loud sounds.

Dynamic range can be considerably broadened by the use of special volume expanding circuits whose function is to give considerably added amplification to a loud sound; in this way the contrast between loud and soft notes is widened. It is beyond the scope of this article to discuss circuit arrangement of such devices.

Plnally we come to the Question of perspective in sound reproduction. In listening to an actual performance of an orchestra, the combined effect of our blnaural he'aring and eyesight gives an effect of three dimensional sound. In single channel electrical reproduction, this effect is totally destroyed, and the effect is one dimensional only.

This disadvantage could be satisfactorily overcome bj? using, during the actual broadcasting or recording as the case may be, three microphones, each connected to a senarate channel, and located one at the centre and one to either side of the orchestra.

The output from each microphone would be taken to a separate transmitter in the case of broadcsstlng and and a separete cutting head in the case of recording. Such an arrangement would of course be quite impracticable due to the expense in- volvefJ- ^ .xi J To receive a broadcast transmitted by such »n arrangement the listener

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items. would have to have three separate radio receivers while, to play records made by this arrangement, three separate pickups would have to be used.

An Illusion of two dimensional sound is obtained by using two or more speakers so that the required frequency

RAO/O THEORY range is shared between them. A common arrangement Is to allow the speaker to handle low and middle frequencies only.

In some cases a single amplifier is used with a frequency dividing network between amplifier and speakers so that each speaker will be supplied with the appropriate range of frequencies. In more elaborate systems two channel amplification is used, one channel amplifying low and middle frequencies and excluding high frequencies and the other amplifying high frequencies only.

By suitable positioning of the two speakers it is possible to give an Illu- sion of breadth to the reproduction, so that low and middle notes come from one part of the room, while high notes come from another part of the room.

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RADIO AND HOBBIES FOR JUNE, 1945 PAGE TWENTY-THREE

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PAGE TWENTY-FOUR RADIO AND HOBBIES FOR JUNE, I94S

RADIO THEORY

COMPLEX WAVES UHEIR APPLICATION

ADDING A WAVE SHAPED TO THE RADIO GENERATOR

Considerable atfenHon has been given, in recent times, to a method of amplifier testing which employs complex rather than simple sine waves. While only a limited number of readers will be interested in the practical side of the question, the following article will nevertheless make interesting reading for others who are anxious to know something of the

theoretical aspect.

By Ernest Steen

IN the latter portion of Hie article, instructions and circuits are

given showing how a wave-shapcr may be added to the Audio .Signal Generator described last month.

The conventional method of testing amplifiers is to feed a pure sine wave to the input and to design for equivalent purity in the output.

Although valuable and widely used, such a method does not tell the full story. In the first place, audio equipment is hardly ever operated with sine wave input under actual working conditions. In fact, the ultimate waveform generated by an orchestra or by a group of singers is a very complex quantity Indeed. Even a single voice produces something far removed from a sinusoidal waveform being, as we know, rich in harmonics and over- tones.

Apart from mere frequency response some means is obviously essential to

(a) (0)

Figure I. Illusiraling how an irregular waveform rasulfs from fhe combination

of two or more pure sine waves.

determine the ability of equipment to handle complex input, without intro- ducing intermodulation between harmonics generated within the apparatus and those supplied as part of the input signal.

Another major consideration is the effect produced on an audio amplifying device by a very steep fronted wave, or loud transient sound, such as from a percussion instrument.

The above points are admittedly highly ccxitroversial, but the various opinions are mainly divergent on the score of measurement, rather than on the existence of the phenomena. As I see it. the subject can be treated in two ways—one is purely abstract and mathematical, the other practical and straightforward; the latter forms the substance of this article.

The logical "first step" is to find an input signal which approaches, or has the salient qualities of the actual working input condition of audio equipment. This it not unduly difficult, as essentially, all that is required is the output from a distorted (yes distorted!) tone generator.

This should be easy to follow, if we bear in mind that any old waveform at all can be resolved into individual component waves which are all sinus- sldal in form. This holds true for all conceivable waveforms. The only point is that, the more angular the waveform, the more numerous are the individual frequency components which compose it.

A simple illustration is given in figure 1, where a fundamental frequency (a) is combined with a harmonic (b) to produce the resultant wave shape (c). Certain definite phase and amplitude re- lationships are, of course, assumed and an alteration to either relationship would have a pronounced effect on the resultant waveform (c).

Although any sufficiently complex wave would meet the requirements set out earlier, there is the additional consideration that any change introduced by the equipment under test must be capable of easy interpretation.

Usual practice is to adopt as near to a square wave as possible, so that

it is relatively easy to note any discrepancy In the output wave. Of course, very little audio equipment is actually called upon to handle a true square wave in practice, but it is an exacting and most informative test,

exactly square or rectangular is not always easv to obtain

in practice, especially with strictly limited equipment. However, provided one can compare directly the input and output from an amplifier, a slight departure from true squareness in the waveshape is not reallv detrimental.

By this time you will have an idea of the set-up involved in testing audio apparatus with a complex input. A Cathotje-Ray Oscilloscope is obviously essential, and the complete set-up is illustrated In figure 2.

Some provision must be made to switch the C.R.O. from input to output in order to compare the two waves. Changing over leads and hooking up in the usual fashion is hardly sufficient, because it is desirable to look at input and output waves in rapid succession, so that an exact comparison can be made.

We come now to the Important matter of determining the significance of the various deviations of the output waveform from the input. The tvpical diagrams in figure 3 presume that a square wave input is used, but slight deviations can be allowed for. Only a few of the many variations can be shown, but these are sufficient to set the general principles.

At a later date, it may be possible for us to put together a full-length article on the subject of wave pattern interpretation, but the examples given will have to serve for the time being.

A point which has doubtless occurred to some is "what should be the fre-

Complex Wave Generator

Amplifier Under Test

o-

(Ui)

C.R.O.

Figure 2. Typ- ical sef-up for testing an amplifier with square-

wave input.

An wave

quency of our input wave?" The answer is that substantially only one or, at .the most, two frequencies are required for rapid assessment frequency response.

Since a complex wave (approaching squareness) has harmonic components extending well beyond the audible range, signals of 1000 (fundamental) tell a pretty complete tale of quality, especially in the upper register.

A 50-cycle fundamental may tell you the awful truth at low frequencies and certainly up to and beyond 1000. So there you are!

There is therefore little immediate point in generating a square wave of a frequency higher than 1000 cycles, as this will more than show the limi-

(Continucd on Next Page)

Figure 3, showing («j a fruo square wave; (b) poor low frequency response; (c) poor high frequency response with evidenf phase shiff; H

n h Ss

A A

(a) 1 C<W w

r jw-

r —

(d) -J fe) A/w- nJ W

Id) Over-compensefion of low frequencies; excessive gain and lack of damping at high frequencies; (f) effect of a

tuned circuit at for tone control or in a poor transformer.

RADIO AND HOBBIES FOR JUNE, 1945 PAGE TWENTY-FIVE

RADIO THEORY

COMPLEX WAVES ■■■ Continued

/ \ / \ tremely exacting and are quite likely ' \ / \ to reveal also any unsuspected faults ' \ i \ In the time base circuits of your C.R.O. I ' 1 or In Its amplifier and Input arrange- I l I l ments. You may find It necessary to l I / I make some Improvements here, before

, / I / 1 . your square wave generator can tell if \ 1 \ f Its story effectively. 1 / 1 / If Refinements like a high-speed trig- T ' ■' ' ' gered time base (hard valve) and a \ i \ . \ I cathode follower input are necessities

. / \ , . / for really serious and rigorous work \ / v , \ / on complex waveforms, although we

«» " humbler folks can get along well . . enough with more conventional equip- f-igurs 4. Something very close to e ment.

square wave can be obtained by clip- Well, I feel that the foregoing will ping the tops from a high amplitude give something to work on and import

sine-wave, as illustrated. a Mtle knowledge of complex waves and the story they have to tell,

tations of any audio frequency device. * * * The fact that our audio generator The next requirement is to describe may give a continuous frequency the addition of a wave-shaper to the coverage is incidental. audio generator which has been so

Just to round off the article - — - | as far as you have gone— 6V6-6 { 6N7 -c rs _ 1 _ nM 1._. 1 t» T I I I I _ . . i

much to the fore in the past twi issues. There is actually not mucl point in adding the extra circuiti unless one has eccess to a cathode ray oscillograph, for visual inspectid of the input and output wave patter] is essential.

A C.R.O. is, of course, invaluabK with a straight-out sine wave genera tor, but there are plenty of jobs whicl a pure audio source will do, even with' out this very handy instrument.

A simple way of obtaining a wav< that is substantially square is to feet a high amplitude sine wave into ar amplifier stage which automatical!! clips the peaks in either direction as illustrated in figure 4.

The general idea is to operate tin stage with zero bias and under conditions where its plate swing is strictlj limited. The sine wave input signa is fed to the grid through a series resistor so that, on the positive signa! swing, the grid draws current and the lowered impedance effectively short; most of the signal peak to cathode.

On the negative peak, the plate cur-

figure 3c is of special in- P | terest, because it discloses , i effects caused by leakage in- -ll-f ductance and stray capacity If )| 1 > which form tuned circuits in 1^ M . i transformer-coupled ampli- i fiers. It reveals also the dan- /Judie ' ger of using inductance in Generator _ j tone control circuits without " careful investigation into 1' capacitance effects, damping and phase shift.

Don't be too disheartened if your much prized equip- , ment does not show up to ad- ngure 5. Wave : vantage at the first test, be- illuitrafad above, cause complex waves are ex-

6N7 or similar

; 6/6-<5 I CotkoeLQ | Follouie* 4

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incorporated in the main circuit diagram, figure 6.

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PAGE TWENTY-SIX RADIO AND HOBBIES FOR JUNE, 1945

RADIO THEORY

rent reaches cut-off, after which further excursion in signal voltage can have no effect on the output circuit. The result is an output signal which is clipped in either direction.

For advanced work, the usual wave- clipper circuit is along the lines of figure 5, in which the clipping action takes place in each of two triode amplifier stages. The ultimate output from this two-stage clipper is a wave very square indeed. For compactness, it is usual to employ a twin triode, although two separate valves can be used if need be.

Although specific values are given to

purpose, the possibilities were investi- gated of using a single stage wave- shapqr—and with very gratifying results. The circuit finally evolved is shown in the maip diagram and you can incorporate, this or figure 5, just as you like.

In actual fact, the waveform derived with the single 6J7-G is as near square as the C.R.O. was capable of showing except for a suspicion of roundness on the leading edge of the negative half-wave.

The 6J7-G is used as a pentode amplifier, with zero bias and a series grid resistor to aid in the clipping

chassis between the generator output and the cathode follower.

Whichever circuit is used, therefore, it will be necessary to instal a double- pole rotary switch to cut the clipper into circuit when necessary. The switch connections are shown in both figures 5 and 6. The rest of the circuit (generator and cathode follower) has been explained at length in previous issues, so that further discussion should not be necessary here.

To avoid 'the necessity for long leads to the switch, it is highly desirable that it be mounted on a small bracket in proximity to the wave-clipper

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Should be 50 mfd. 200 P.V. Or simlUr for a satisfeotory square wave at low frequenoiea

Figure 6. The complete schematic circuit diagram with wave . shaper and cathode follower. The basic sine wave generator 1

remains exactly as described in previous issues.^to which refer- I ence should be made for construptionai data and adjustments. Condensers C8 to Cll may be single .0004 mfd. R-C o? units, two 2-gangs or one 4-gang; note that one pair of rotors MAINS must be insulated. Condenser "C" is adjusted to give level output at all settings of the main tuning condenser. Average values are 40-50 mmfd. with the single gang or 2-gang

I arrangement but up to 150 mmfd. is necessary with a typical [ 4-gang tuning condenser. Control R8 Is set to" a position ■*7 ) ensuring consistent but not excessive oscillation at all fre-

quencies; once set, it should not be altered. Resistors in the | tuning network should be paired as accurately as possible, but careful selection [ by cut-and-try methods will ensure equal output %on all bands. Continuous

, coverage on square waves is not necessary, and effort should be concentrated I on getting a good wave shape at about 50 and 1000 c/s.

80 mA. Chokes

5Y3-Q

To niain. Chassis

J tuning network should be paired as accurately as possible, but careful selection i socket. It is then controlled from the I by cut-and-try methods will ensure equal output %on all bands. Continuous J panel by a length of iin. shaft and J, coverage on square waves is not necessary, and effort should be concentrated 1 an ordinary flexible coupling. ! on getting a good wave shape at about 50 and 1000 c/s. , J By arranging matters so that the

t knob comes just below the jack and to the left of the output control, a

act as a general guide, the constructor action of the grid circuit. The plate balanced panel arrangement is ob- must be prepared to do a certain and screen feed arrangements are tained. The control knob should be amount of experimenting to get things rather unorthodox, but were deter- marked "sine-wave" in one direction just right. For example, the two mined by experiment to give the best (preferably clockwise) and "Square- series grid resistors .may have to be results. wave" in the other, shunted by a small capacitance to Actually, the constants in the grid is worthwhile making some at- preserve the high frequency response circuit snd in the plate and screen tempt to get the amplitude of the and the angulai characteiistics of the circuits had to be veiled to give a square wave roughly equal to the generated square wave. From 5 to balanced wave. Unless things are just rms value of the sine wave It should 50 mmfd. should suffice, depending right, one half of the wave is likely "e very close with the 6J7-G arrange- on circumstances. to occupy a greater time interval than nient shown, but slight alteration can on circumstances. to occupy

As stated earlier, square waves are the other net only very revealing as far as the Since l amplifier is concerned, but they are depends

Since the. operation of the clipper depends largely on having a high

subject to alteration in the very devices input signal, it is more or less essen-

be effected by modifying the grid input circuit.

Because capacitive effects intrude to a marked degree, difficulty will be

used to generate them and make them tial that the stage should immediately experienced in obtaining a square visible. follow the 6V6-G valve of the basic wave over the whole frequency range

Realising the shortage of twin triodes sine-wave, generator. Tt was with this of the oscillator; in fact it may be and the natural aversion to using two in mind, last month, that we sug- valves for what might seem a secondary gested leaving a vacant hole in the (Continued on Page 29)

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PASS TWENTY-EISHT RADIO AND ROBBIES FOR JUNE, 1945

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Figur# 7. Showing the location of the wave shaping stage and the associated control. The once vacant

chassis and panel are filling up.

Figure 8. An underneath view of the chassis with the square wave shaper installed. Note how the switch is mounted near the socket, with an extension spindle through to the front panel. This desirable arrangement, eliminates the need (or long leads I between the oscillator and output I

circuits. i 1

Impossible with the conventional circuits and construction employed.

However, as we explained earlier, there is little point In seeking to ac- complish this, since only a couple of spot frequencies are really necessary. Concentrate on getting a good square wave in the region of 50 cycles and 1000 cycles and regard anything more than this as merely incidental.

The middle frequency setting will be easy enough, but some difficulty can be expected at 50 cycles. 'Jf the square wave exhibits the characteristics of figure 3b, start looking for inadequate coupling condensers somewhere along the line. The' bigger the coupling condensers the better, provided the extra capacitance does not involve undue d-c leakage.

While all these adjustments are being made, the generator as a unit should be feeding directly into the terminals of the C.R.O. And remember that there are coupling condensers in the CRO and cathode and screen bypass units, which may not be large enough for the purpose, although adequate for ordinary sine wave observations.

When you have obtained the de- ilred square wave at the two main test frequencies, and can inspect it properly on your C.R.O.. then and only then, connect an amplifier into circuit and see how things shape up.

Used intelligently, the square wave generator may show just why those two amplifiers sound so different, even though they are both "as flat as a board."

Attention is drawn to a note on the main circuit diagram. The design of the output attenuator is adequate for sine waves, but a difficulty became when the network was called upon to handle square wanes at about 50 c/s. The 8 mfd. coupling condenser proved

inadequate and tests showed a high- capacltance lower voltage type to be essential. You may have to approach the manufacturers for a unit of this nature. Returning the 6J7-G suppressor to the output terminal is a "free" feedback loop which helps matters.

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RADIO AND HOBBIES FOR JUNE, 1945 PAGE TWENTY-NINE

f RADIO THEORY '

T T

In our lost issue, we discussed at some length the operating conditions which obtain in a conventional transformer-coupled amplifier stage. The present article outlines the chief design requirements for an interstage transfbrmer and then describes various special circuit arrangements which are sometimes

adopted in the interests of fidelity.

Sixteenth Article in the Series "Radio Valves and Their Application."

AS already explained, the bass response depends very largely

on the inductance of the primary winding. In general terms, and considering only a single stage, it is desirable for the inductive reactance of the primary to be equal to or greater than the plate resistance of the valve at the lowest frequency which it is desired to reproduce without perceptible loss.

Prom basic formulae It is evident that the inductance of a coil increases roughly as the square of the number of turns so that at first glance, it would seem that inductance can be pushed up to any desired figure, simply by adding ejctra turns. However, there is a catch to it!

Every extra turn added to the primary means extra distributed capacitance across the winding, which is evident, in effect, as a bypass capacitance between the plate of the valve and earth.

Furthermore, if a given step-up ratio Is to be preserved, any Increase in primary turns has to be accompanied by a corresponding increase in the number of turns on the secondary winding Here, too distributed capacl-

B_ __ __

' 'C' N v \ \ s \

10 100 10 00 lOO'OO

ifigs, some manufacturers divide the primary and secondary windings into two or more sections. These are in- terspersed either one on top of the other, or mounted side by side along the core as narrow spools.

The quality of a transformer is influenced considerably by the nature of the iron which composes the core. Actually, inductance varies directly with the permeabilitv of the iron, so that an improvement of two to one is immediately reflected as a corresponding improvement in the figure of primary inductance.

With this point in mind, transformer manufacturers have long since employed special alloys and special grades of Iron having higher figures of per-

Frequency C/S Figure I. Typical response curves (or three transformers under ordinary conditions: (A) is a modern high-grade type. (BJ a transformer exhibiting sustained bass but poor treble. (C) a cheap unit with poor overall response.

tance gives the effect of a condenser between the grid of the following valve and earth.

The net result is a diminution of the high frequency response, so that what is gained at one end of the frequency band is likely to be lost at the other. Furthermore, with the inductive properties of the flansformer, the capacitance tends to produce sundry resonance peaks, which can have a particularly distressing effect on reproduction'.

In an effort to minimise distributed capacitance and, at the same time, to improve the coupling between wind-

Bh Bias or Earth

Figure 2. A shunf-fed transformer using an audio choke. The scheme may be good or bad, depending on the overall characteristics of the combin-

ation. meability than ordinary iron lamina- tions.

An increase in primary inductance by these means is obviously desirable, since the bass response is improved without compromising treble.

However, the core is not immune to outside effects. In the conventional transformer-coupled stage, the primary winding is required to carry the plate current of the associated valve, and this may be anything from one to 10 milliamas in typical cases.

This current tends to magnetise the iron in the core, affecting its magnetic properties and its permeability. The final result is a reduction in effective primary inductance, depending on plate current, and a possible deteriora- tion in othei^ characteristics.

In designiift an audio transformer, therefore, it is necessary to effect a comprcmke between numerous con- flicting factors. In the "twenties," overall gain was the vital consideration and the interpretation of the term fidelity wRs nearly synonvmous with jn- telliaibility. Little wonder that most of the old-style transformers are hope- less from a quality point of view.

With the development of better core materials, a more complete understanding of the relevant problems, and the demand for higher fidelity, a vast improvement has come about so that the best modern inter-stage transformers leave little to be desired.

Figure 1 shows the curve (A) of a high-class transformer; the response is seen to be substantially flat within the whole of the useful musical range. Curve (Bj is for a transformer in which the bass response has been sustained at the expense of the treble, while (C) is for a cheap or old-style transformer with a very poor overall response.

It has been assumed in the foregoing that the transformer is used in the conventional way, the primary winding constituting the plate load for an ordinary general-purpose triode valve. Under these conditions, as pointed out last month, the plate resistance of the valve is a gorerning factor on the performance of any given transformer.

PLATE RESISTANCE Most general purpose triodes have

a plate resistance of from 10,000 to 15.000 ohms, A lower value would tend to minimise capacitive difficulties in the treble register, and inductive losses at the bass end. However, valves "having lower values of plate resistance normally draw higher current; this reduces the primary inductance still further, offsetting any advantage gained. Furthermore, there is a definite limit to the current which the fine wire in the winding can safely carry.

It follows that a general improvement. In the characteristics of any transformer can be expected if a circuit arrangement is found which would relieve the transformer primary of the task of carrying the initial d-c plate current of the associated valve.

Such a circuit arrangement is illustrated in figure 2 where the plate current flows through a special high In- ductance choke. The audio voltages generated in the plate circuit and across the choke are communicated to the transformer primary by the coupling condenser Cc.

Though the circuit is often employed, it cannot, and should not, be regarded as one which automatically ensures fidelity. Much the same problems are encountered in the design of an audio choke as in a transformer. It suffers the same diminution of inductance, due to plate current, and similar capacitive effects intrude. The design is onlv simplified by the absence of a secondary winding.

OBVIOUS REQUIREMENTS Obviously, if any benefits are to be

obtained, the parallel Inductance of the choke and the transformer primary must be adequate for the as- eociated valve, and the parallel capacitance effects of all three windings must, net be unduly high

If the audio choke has adequate inductance and Cc is large, the operating conditions for Vl arc essentially the same as for a conventional transformer coupled stage (see figure 4 last issue). The effective plate voltage is substantially equal to the high ten-

PASE THIRTY RADIO AND HOBBIES FOR JUNE, 1945

kADIO THEORY slon supply, and the load is reactive In character.

The variable nature of the load ne- cessitates using a triode in the position VI. exactly as for the conventional circuit arrangement, However, by suitably designing the choke, it is possible to use a low-impedance, high- current triode for any special requirements.

In figure 3 is shown a comparable but more widely used circuit, in which the audio choke is replaced by a resistor. This forms the d-c plate load for the valve, and the audio voltages developed across it are communicated to the primary winding by means of condenser Cc.

For determination of the operating conditions, VI should be regarded as being resistance coupled and the graphical analysis is exactly as described in the April issue (figure 2).

OPERATING CONDITIONS The load resistor is selected with

due respect to the nominal plate resistance of the valve, being usuallj about five times this latter value. Th( equivalent load line is then drawn cr the curves and a working point selected to ensure linearity and adequate audio voltage output.

Knowing the required bias and the operating current, it is then a simple matter to work out the cathode bias resistor.

With figure 3, the effective plate voltage of VI is approximately half the high tension supply so that, for moderate supply voltages the peak audio output from figure 3 is less

" V

10 1000 1000 10000 Frequency C/S

Figure 4. Illuitrating the effect of different values for Cc on frequency

response. to use a reliable condenser between plate and transformer primary.

Actually, the capacitance of thh condenser is quite important, for. witv

the primary winding it forms a series- resonant circuit. Near the series resonant frequency, the audio current,- hrough the primary tend to increase and the resulting rise in response maj be good, bad cr indifferent, depending on iust where it occurs in the frequency spectrum.

If Cc is very large, the resonant frequency may occur well below the

audible range and at a frequency where the overall response is in any case limited by other factors, under these conditions, the frequency characteristics of Cc can largely be ignored,

At the other extreme, a low value for Cc can produce a prominent peak in the bass register, below which the response falls off badly. This condition produces an unnatural "thump" effect in all bass passages, and it should be carefully avoided. For a. good transformer at least Cc cannot be made too large, but it can be too small.

If the primary inductance of the transformer is known accurately, the resonance effect can actually be employed to offset to seme extent the ill-effects of Inadequate primary in- iuctance.

For example the response with a mor transformer, may naturally tend to drop off below about 90 or 100 c/s, Bv resonating the circuit in the range 40 to 60 c/s, the response can be boosted, as illustrated, in figure 4. 'however, proper utilisation of this effect calls for a knowledge of the primary inductance or means of -becking the position of the resonant neak.

Irrespective of the particular man- (Continued on Page ffij)

.mess

B+ Bias or Earth

Figure 3. The more usual shunt-led circuit, employing a resistive plate load. Some transformers may be used

only with this circuit. than from figure 2. However, this disadvantage can be offset by increasing the high tension supply for VI (figure 3) to«a point where the effective plate voltage becomes equal to the permissible maximum voltage rating of the valve.

The true a-c load for the valve is an extremely complex quantity, which varies with frequency. In general, the load takes the form of a narrow ellpse.

It is interesting to note that some modem transformers are intended only for "shunt fed" operation; in particular, the circuit of figure 3. They use a special core material which has a very high figure of permeability, and any attempt to draw direct current through the primary actually ruins the characteristics of the transformer by its magnetising effect on the core.'

The special core material and appropriate winding technique makes possible a flat response from something like 20 to 15,000 c/s, with negli- gible distortion.

To ensure this fidelity and to safe- guard the transformer, it is essential

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PAGE THIRTY-TWO RADIO AND HOBBIES FOR JUNE, 1945

(Continued from Page 31) ner in which the transformer is connected, the .output voltage across the secondary winding is related to that across the primary by the ratio of turns. Modern practice is to work on a step-up ratio of about two to one, although some transformers go as high as three to one.

The overall stage gain from the grid of VI to the grid of V2 is. therefore, the product of the valve and transformer gain. In practice, it may be anything from 20 to 60 times.

This is higher than can be achieved for similar valves with resistance coupling, but considerably less than a resistance coupled pentode, under opti- mum conditions.

An Interesting circuit, which has received considerable attention in recent times, is illustrated in figure 5. Instead of being connected in the actual plate lead, the transformer primary is connected between the cathode of an indirectly heated valve and earth. The plate is connected directly to a high tension supply source.

AFFECTS CHARACTERISTICS This so-called "cathode coupling" Im-

parts several unusual characteristics to the stage. One obvious and gener- ally undesirable effect is the drastic reductions in gain.

The signal current variations through the valve set up corresponding voltages across the transformer primary in precisely the same manner as would occur if it were directly between plate • and B-plus. The output voltage is thus derived between the cathode of the valv e and earth

In this position, however, the entire out voltage is present in the signal input circuit between grid and cathode, and the phase is such that it opposes the action of the input signal. For any given output, therefore, the total signal Input must be equal to the output voltage plus the necessary grid-cathode signal voltage.

In a typical case the voltage across the primary winding can never be

Bias or

Blaa or Earth

Figure 6. Showing how a traniformer is utilised for a push-pull output system.

for an average figure of 1.5 milliamps per volt, the output impedance becomes something like 600 ohms, or about one-fifteenth the normal inter- nal plate resistance.

The actual plate current through the valve remains much the same, so that' the circuit arrangement greatly reduces inequalities in response due to inductive and capacitive losses. The feedback also reduces actual harmonic distortion within the stage.

Cathode coupling is of little value for ordinary voltage amplifier stages, where high gain and high fidelity can be obtained quite cheaply with, say, a resistance-coupled pentode.

However, It has many advantages to offer in coupling to certain output valves and for certain of their oper-

■atlng conditions where a low-impedance,, low-resistance signal input circuit is required. Cathode coupling makes it possible to meet this requirement with an inexpensive transformer whose frequency response, under other conditions, would be only mediocre.

Figure 5 presents the bare fundamentals of a cathode follower stage. It assumes, for example, that the d-c voltage drop across the transformer primary is a suitable bias for the associated valve. This may or may not be so. In some cases it may be necessary to provide additional resistance

ftA D/O T H SORY

in the cathode circuit, or to reduce the effective bias by returning the grid resistor to a point slightly positive with respect to ground.

The whole subject of cathode coupling is a rather extensive on?, but the foregoing will give some idea of the operation of the circuit.

PUSH-PULL CIRCUITS To conclude this article, it is fit-

ting to make mention of the ease with which transformer coupling can be utilised for push-pull operation, irrespective of the method of connection. For this purpose, the secondary winding is centre-tapped, as shown on figure 6.

Audio voltages are induced in the secondary in the usual way, but the ends are connected to the grids of V2 and V3 respectively, and the centre- tap is returned to earth or to bias.

The signal voltages applied to the two output grids are therefore out of phase. When the grid of V2 swings positive, that of V3 swings negative, and vice versa.

Push-pull output systems are widely used in amplifier equipment, for reasons which will be better under- stood when the subject of power amplifiers is discussed at a later date. Sufficient to say that, by this means, comparatively high power output and good fidelity can be obtained with a minimum expenditure and trouble.

ADJUSTING CRYSTALS \ NEW production technique for

quartz crystals iises X-rays to adjust delicate plates " to their final frequency at the rate of thirty to fifty cycles, a minute. Plate®, for the six to felght, megacycle Tange can be lowered up to three kilocyqjes by X-iBy exposure. (Since the frequency can be, checked Continually during the treat- ment, the crystal can be removed from the exposure the instant it reaches the correct frequency. The equipment developed by the North American Philips Company employs a new high- Intensity water-cooled X-ray tube. Experiments made by the Reeves Sound Laboratories show that frequency change is permanent beyond any tem- perature range crystal is likely to experience.

RADIO'S WARTIME PROGRESS

Figure 5. The essential features of a cathode-coupled amplifier. It gives low gain but is capable of aicellent fidelity and has a very low output impedance.

greater than about 0.9 times the signal Input. Allowing for an ordinary step- up in the transformer, the overall stage gain is therefore limited to a mere two or three times.

Actually, the common cathode circuit produces a form of negative feedback. While the loss of gain is gen- erally undesirable, there is a notable effect on the operation in so far as it affects the transformer.

It can be shown mathematically that the output Impedance of the valve is roughly equal to 1 divided by Gm— the mutual conductance. Allowing

AT the annual meeting of the Insti- tution of Radio Engineers of Aus-

tralia at Science House, Sydney, the president (Mr. A. S. McDonald) stressed the important role radio and associated arts were playing in hastening victory.

Mr. McDonald said that during the year there have been many new radio developments of world interest. Prin- cipal amongst these are obstacle detec- tion, blind landing of aircraft, radio altimeters, and radio relaying by V.H.F. of voice and vision.

P.M. and Television continued to receive a considerable amount of engineering effort. Emerging out of this effort are the tendencies (U to propa- gate television programmps on frequencies between 50 and 350 mcs, and the use of amplitude modulation in preference to frequency modulation for the reason that the latter, in being reflected from all sorts of reflecting bodies, cases multiple images which are objectionable; (2) in P.M. stations

to increase the permissible frequency swing to lOOkc., or even 125kc.

The expanded use of V.H.F. has brought in its train a number of problems, the principal perhaps being insulation. These very high frequencies cannot be contained within or upon a conductor, but tend to spread out through the adjacent spaces, often causing so much heat in "insulation" by di-electric losses that the insulation fails. The tendency is towards the use of wave guides.

In the Induction heating field, progress has been made particularly In plastics, where considerable time has been saved by electronic heating of "preforms." Various frequencies are used for various functions. For instance, it is common practice to use approximately 100 to 300 cycles for melting non-ferrous metals, 1000 cycles for large steel furnaces, 3000 cycles for small steel furnaces, 10,000 cycles for hardening of steel, .1 to .5 mcs, for braz. Ing, 2 to 20 mcs. for electronically heating plastics and plywoods.

RADIO AND HOBBIES FOR JUNE, 1945 PASE THIRTY-THRW

DX NOTES

BROADCAST BAND DX

With the fall of some of Europe's largest cities more and more broadcasting stations change from Nazi to Allied control. Already we have heard in our news broadcasts of the capture of "Station Hamburg," now called "Radio Hamburg." Calls have come for outside help by British and anti-Nazi Czechs from Prague Radio, whilst several "Radio and Hobbies" readers report hearing broadcasts in Russian from the

powerful transmitter in Breslau, Germany.

1ZM Auckland leaves the air. Many well- known Australian features are rebroadcast.

WVTK appears to be hoard by numerous r ' bulle

IT is not likely that signals from Europe will reach Australia clearly

on the broadcast band for the next few weeks, but DX'ers are advised to watch for an Allied-controlled transmitter at Rangoon, Burma. . „

While new of Allied success In Europe Is encouraglnE, we received the other day a sad reminder that our boys still have a ob to do up North. A letter was sent In

jy Mrs. E. Head, advising that her only son. Graham lone of our DXersI has not been heard ot since he left his base on a reconnaissance flight over the Timor Sea.

Numerous reports have been received from Graham Head of Blackwood. Bunylp, Vic- toria and his name will therefore be missed In these columns by our readers, as also the non-arlval of his Interesting letters.

From Mr. Gaven Kelly, we learn that, as the result of a dispute with Gymple Broad- casters Pty. (40 Y i. the Gymple Traders Association approached the Federal Govern- ment for a licence to operaxe a broadcasting station at Gymple, on a co-operative basis. The association objects to alleged preference at peak listening times being given to Brisbane and national sponsors by 4GY. The management of 4GY was asked to devote the period 7.30 to 8.30 pm. Monday to Saturday, to advertisements from local sponsors. Agreement was not reached and, as a result, several Gymple sponsors have apparenllv cancelled their contracts. Wo were pleased to make the acquaint- ance ot two more keen "Radio and Hobbles" readers one Sunday morning In April. Mr. Bill Belford, and Mr. Dave Harding, from Chullora, brought their verification cards and letters over for our Inspection, and took the opportunity to chat about DX In general There was speculation as to the possibilities of receiving a verification from the American transmitter on Salpan Island. So far as we know, no verles have been received from this station.

We were pleased be see again Mr. Stuart Kerr who Is. at the time of writing, stationed near Sydney, preparatory to moving North. Stuart added verles from 2KO, 3TR and others recently to his collection.

A * * At many centres throughout the war-torn

world, where large numbers of allied light- ing men and women are stationed, radio transmitters have been Installed In an attempt by the governments of United Nations to .keep the trops In those areas posted with the latest news from other fronts, and to provide them with the best possible radio entertainment. Several such transmitters have been received by listeners In Australia, despite the low power used by many.

From the latest issue of the New Zealand I>X Club's bulletin, "DX'tra," we learn of a chain of AEF (Allied or American expedi- tionary Forcesl stations known as the Jungle Network, and Mosquito Network. No fewer than 11 transmitters ore In use, while 15 stations comprise a similar chain In another section of the globe, known as the Pacific network. The Americans alone operate 154 transmitters, ranging In power from 50 to over 180,000 watts. The British use 44 stations In their AEF network. 16 In the Alas- kan area. 20 In the Par East, Burma. Ceylon. China and India, eight In the Mediterranean network: and. of course, we must not forget the several transmitters operated by the Australian authorities. Only station lost to the enemy was at Kwellln. China, which had to be destroyed In a general retreat.

At Balpan, a station was Installed aboard a freighter. Even American airmen In the USSR are catered for by a transmitter at Moscow. The first Allied-controlled transmitter on Beyle was Installed on the 50-year- old Australian vessel Apache, with a special broadcasting stud'" (upit-ln between decks. Transmission for Pressmen wes also Srovlded from this station, from powerful

•ansmllters, beamed to San Francisco.

Two weeks after the AEF station. VU2ZY at New Delhi, India (BOw.) took the air, all radio receivers within a radius of 50 miles had been sold out. 880,000 transcription discs have been provided by the APRS. Much of the above Information Was taken from a S.W. broadcast heard by an NZDXC member.

Verifications have been received from two f'o'lons In the Jungle Network, WVTA and WVTH. Reports to any WV station may be

rÊPORTS for fhe July issue should '• bo posted to roach Mr. Roy Hallotl not lator than Saturday, June 2. His address is 36 Baler-street.

'Enfield, NSW.

addressed to the American Army Education and Information Detachment Headquarters, Far East. C/o Radio WVTH, APO 322, AEF Noumea Is a member of the Mos- quito Network, and Is probably the station heard at best signal strength In Eastern Australia. At our location the station Is heard from around 5.15 pm till alter 9 pm, broadcasting transcriptions of radio programmes heard originally from stations In the U.S. News relays from short-wave stations In San Francisco are heard usually on each hour. This station has sent letters acknowledging receipt ot reports to several DX'ers

One Saturday morning reclntlv, WVTG was heard here playing requests for members of the. forces till 13.45 am. A medita- tion programme was heard then until closing, with the American national anthem at I o'clock. WVTA has been heard on the air as late as 3 am Thursday and Sundav mornlngs. while WVTH has been reported closing at midnight, except on Saturdays, when they continue Into Sunday morning.

9PA Moresby, the station operated by the ABC, Is on a clear channel from 9 pm, when

readers at fair level, a news bulletin being broadcast at midnight, the .time at the transmitter then being 11 pm.' WSYJ occupies Its time playing gramophone records.

In some cases, locations of some of the stations listed here may not be correct. Mr Baker, for Instance, suggests Salpan may be the location of WVTK, while Mr. A. Towns. King Island, feels confldent he heard the announcement. APRS. Voice of Leyte, around 8.30 pm. Several locations have been shown In the past i<* WVTA. The latest information, coming from LAC G. Peterson, leads us to believe this station is operating- now from Hollandla. Perhaps WVTA. like other AEF units, moves forward as our troops advance. RAAP Radio, ex Milne Bay. Is operating now from Madang.

We trust the following list of stations heard by our readers may be the means of helping others log some of these stations:

3S3kc.—AEF station of the BBC, 5.30 am. 670kc.—WVTI Bougainville, 5 am. 690kc.—Guadalcanar, 5 am. 975kc.—AEF Noumea New Caledonia,

around 5 am, and from sunset till about 9 977kc— ABSLE (American Broadcasting Station In Europel.

lOlOkc.—Salpan Island. 1045kc.—APRS Esplrltu Santo. New Heb- rides. 5 am and at night. <

I050kc.—AES station of the BBC, 4 am. 1122kc.—ABSIE. London, England, 4 am. ITSOkc.—R. A.A.F. Radio, Madang. New

Guinea. I240kc.—"Voice of the 8th Army." some-

where In Italy. 3 am. 1250kc.—9PA Moresby. New Guinea, heard at night. 1320kc,—WXLE. Enlwetok, Marshall Islands.

1323kc.—WVTA Hollandla. New Guinea. 1340kc.—WXLP, Tarawa. Gilbert Islands. 1340kc.—Australian Army Amenities Radio.

Lae. New Guinea. 1400kc.—WXLM, Makln, Gilbert Islands. HOOkc.—WVTD, Admiralty Islands. 1400kc.—WVTE. Location unknown. I415kc.—WVTH Lae, New Guinea. Til! 1

am. Sundays, Midnight other nights. 1430kc,—WXLG, Kwajellan. Marshall la-

lands. I450kc.—WVTG. Address, APO 920. Heard

here till 1 am. Saturdays, may close same time other nights also.

1460kc.—WVTL. On the air. 8 pm till Mid- night.

USOkc.—WVTP. Address. APO 665. Has been heard till I am.

1480kc.—WVTB. Location unknown. I480kc.—Altape, New Guinea. schedule,

week days 6.45 to 8 am, 4 to 9 pm. afternoon session from 1.15 pm. Saturdays.

USOkc.—WVTG Milne Bay. ISOOkc.—WSYJ, an American 60-watt sta-

tion, somewhere up North. On the air 3 to 6 pm.

I510kc.—WVTK Leyte, Philippines. Heard at night, around 8 to 12 pm.. Interference occasionally from YLAC Nashville, U.S.A.

STATION NOTES AND VERIFICATIONS "AIR. JOHN WEST. Kogarab, NSW, phoned i-'J- us one April Saturday morning, express- ing surprise at the arrival of a verlflcatlnn card from 2HD Newcastle at his home in the morning mall. A few minutes later, our own mall was delivered and we. too, much to our delight, found a card from this staUon verifying our reception of a test transmission, carried out nboul a week before their ofllclal opening broadcast. The card Is white, with the owners' name ("Alrsalos Broadcasters Pty.. Ltd, "I In while letters against a black band along the top ot the card, with the station call-sign against a red shield nearer the left-hand end of the band. Several other readers. A. Zerbst, B. Bakh. and L. Gllddon, have since reported receipt of this card. 2HD operates on 1140kc.

When Mr. Harding and Mr. Belford visited our llslening-post recently, among the verification cards and letters we were shown was the new card from SIX Perth, showing Ihe station call-sign, against a background con- sisting of a scene of downtown Perth. Like the older card Issued by 6IX, showing photos of station personalities In place of the city scene, this card Is cream and brown, and Is well worth adding to your collection. 6IX operates on a frequency of 1240kc. with a power of 509 watts Many programmes are relayed to 6WB Kntannlng, I070kc., 2000 watts, and 6MD Merredln, 500 watts. HOOkc. AJi stations arc members of the major network, and. although as far as we know, a card has not been printed lor BMD. the 6WB QSL card la, like that Isaued by 6IX. very attractive.

Mr. Kelly (Gymplel has three Interesting verifications to toll us about this month. His verification from the 250-walt Wellington NZ transmitter. 2YD. must be one of the few In the country. The card Is the usual pink card, Issued by the National Broadcast- ing Service of New' Zealand, to verify reception of their numerous other stations (2YA, 1YA. Ate. I,

Instead of the black and while PMG card DX'ers have received In the past from 9PA. Mr. Kelly received a letter, deflnltely verifying his reception of this ABC station.

A letter from an engineer at WVTH, I420kc. contains some interesting Information concerning this 50-watt armed forces radio station. and deflnltely verifies ow reporter's reception of the station.

The arrival of our verification card from KRHO proved rather a surprise to us. We had previously heard that, as the result of a report sent to KRHO on one of ihelr shortwave frequencies. Mr. Alan Smith, Coogee, NSW. received a letter. In an interesting envelope, bearing the autograph of a high American war department ofllclal at Hono- lulu. and postage stamps to the value of about 60 cents. Our card Is white, with an outline of the top of the globe at the bottom ot the card, and an aerial mast running up the centre, colored pale blue. The station call-sign appears In large red letters on Ihe bottom left, station Identlfleatlon announce- ments ("Voice of America," &c.l. at lop left. Schedules on short-wave frequencies are on the right of the card. Our report was sent on their transmission on about lOIOkc.

PAGE THIRTY-FOUR RADIO AND HOBBIES FOR JUNE, I94S

SHORT W XV E S

SHORT-WAVE NOTES—BY TED WHITING o

Most of the stations located in the Northern Hemisphere have adopted their summer schedules as from May 1, and we can expect a general improvement in reception. Fine signals are heard day and night except for a brief hour or so in the forenoon. This will soon improve, however, and, by the time

these notes are read, this improvement should be evident.

AS these notes are written, the world lias just received the

nionientous news of the defeat of Germany and great activity is noted, especially from America. Many changes will undoubtedly result, and we hope to include some of these in the station list.

We ore advised that the new Australian transmitters are nearlng completion and two new lOOkw. transmitters will soon take the air under the calls VLA and VLB. The call VLC Is, of course. In operation, using a power of 50kw. Reports on the tests of these stations will be appreciated.

Resource, we believe, Is Inherent to Aus- tralians. One of our renders surely demon- strated this by sending a report to the Russian Legation In the hope that a verl will be forthcoming. Hope that this method Is successful!

Readers are well advised to look over the list of New Stations In this Issue. As usual, our readers are well to the lore In reporting these stations and we will be Interested to learn how many verifications are received for these. ★ * *

Stations operating from the European area 4

are In the news at oresent, and many readers will listen In an effort to act the latest news bulletins. It will be noticed that quite a few familiar signals have disappeared which will be replaced from time to lime. The new "Radio Espana" is heard fairly widely on 9470kc. In addition to other frequencies, the likelihood being that the former will be Us regular position. Vatican City Is heard In a POW news transmission on I5090kc. at 4.30 pm and at 5 pm In a similar service on meokc. SBP mOSkc. at 1 am and also at 5 pm Is heard with some success at times, Paris Is good on 9500, 9505 and 9530kc. In foreign service at 4.50 pm. 9516kc. at 4 am. and on 15240kc. at 9 pm at fine level.

Belgrade on 9505kc. Is audible at 1.15 am and In some locations at 5.15 om. Rome Is a fair one at 7.50 am on 602?kc.. while Lublin Is still heard at quite good strength at 3.30 am.

Prom "Unlversallte" we learn that Athens has been assigned several frequencies apart from SVM. which can be heard calling the BBC at 2 am till after 5 rm. The other frequencies ore SVS. 13725. SVR 13670, SVQ 13640, SVP 12195 at 6.15 am, SVO 11475 and SVN 10705. some of which will possibly become audible as time passes. Prom the same source we learn that TF.I Is heard In America at fine level on 12233kc. at mld- nlehl-12.30am in our time on Sunday. A commcnlarv Is given In Icelandic: this signal should oosslbly be heard here on Sunday. Radio Enlaan has been logged In the past; try for It on n640kc. at 3,40 am-4 am and on 9595kc. at 7.5 am with news. Another Interesting one we noticed In that nubllca- llon was Radio Corse. Corsica, on 7830kc. at 8.10 am. which could be heard here when conditions are In our favor.

The Sw-lss stations are heard well In the transmission for Australia at the new lime of 3 Dm-4.30 pm on 11960kc. and 13955kc. The former Is. of course, the better signal,

Moscow Is good on most of their frequencies as usual, being audible most of the day. * * *

The highlight of the African group Is the reception of Pletermarltrburg 2 by Mr. Cushen at 5.30 am. These Africans are Increasingly hard to hear in N. Zealand, which makes this logging a meritorious one. So far there are no more reports of the SABC stations, but Mr. .Smart has news from a friend of his In S. Africa. The following stations operate fi*»m 6 pm-6.30 pm, 9 pm-9.15 pm: Salisbury on 5990kc. and 15600 kc.; Buln- wayo. 3800kc.: Dmtall. 0080kc. Prom 1.55 Bm-2.30 am and 3.55 am-6 am: Salisbury. 3000kc, and 15600kc.; Bulawayo. SBOOfcc.; Umtall. 3400kc. Hope that we may get some reports out of this. We are Indebted to

Mr. Cackett. Salisbury, South Africa, fot this information.

Radio Somali Is heard at fair level some days In transmission at 2 am. The BBC news carried at 3 am.

Egyptians and Addis Ababa are heard well now on most occasions, while a good signal comes from Tananarive at 11.30 pm on 12130kc. No reports on the outlet on the 49m. band.

CR7BE Is heard at 6 am on 9870kc. CR7BO Is now logged on 4926kc, when, at 1 am. the station opens in English, followed at I 30 am by an American Show.

Brazzaville Is available as usual, morning, noon and night, on several frequencies; we still find 11970kc. the best of them all. The same applies to the Congo stations: In this case 97fl5kc. Is the best.

SHORT-WAVE notes for the July issue should be posted to reach

Mr. Tod Whiting not later than Satur- day, June 2, 1945. His address is 16 Louden-street, Five Dock, NSW.

Kenya Is heard well some nights at 12.31- am on closing; I0730kc. is the spot. Another service Is on 61l4kc. and 4949kc., the service being conducted In several languages.

Algiers comes In at good level on 9610ko, at 4.30 am and. on several days .we have heard the news In French on 6960kc, at 6 am.

Dakar Is a new one In tl405kc. at 7 am. and has been heard on 7210kc. at 7.15 am and at 5.15 pm.

* ■* * Signals from Central America are quite

good at present, and are sure to Improve as winter matures. As we have pointed out repeatedly, Sunday afternoon Is a good time for these stations, as they operate later on Saturday In their time. In addition, it Is found that several of them can be heard In the early morning, and even a few at night.

HP5A Is audible at 11 am on a good day HP5B Is a new one to most of us. being logged recently In Queensland at 10.30 pm. HPSQ can nearly always be heard when HP5A Is on

and Is reported throughout the morning and In the forenoon.

Haiti can still be tuned through the noise on 10.130kc. Other outlets In Haiti are HHCA. 4000kc,. HH2S. 5955kC.. and HHCM. 9660kc.

Dominican Republic stations have been mentioned previously, listings being for those which may be heard In the afternoon Listen for these at 10.30 pm: NIH. 0780kc.: HIL 6630kc.; HIT. 6630kc.; HI1A. 6!90kc.: HIIO. 0l20kc.: HIIJ. o026kc.: HI1N 6245kc.; HI1R. C440kc.; HI2T, 64S5kc.: HI1X, 6380kC : HI1Z. 6315kc ; HI9B. 6385kc. Reports on any of these will be appreciated.

Years ago we were wont to listen to TI4NRH, it we were lucky, and now. after all these years, it Is reported again. Heard with music at 8 am, and possibly heard also In the afternoon, this station will verify. TIPO, 9020kc Is weak now at 10 pm. but some Interstate posts report a good signal. TILS Is another Costa Rlcan heard at limes on 6105kc. at 10 pm; very weak now.

TQNA Is reported from Guatemala on 6225ko. as operating 9 am-1.5 pm; the latter time would be the best. TGWA, IS.nOkc,. is now on the air 11.30 pm-10 am; TGWA, 9670kc. is fair til) 4 pm on Sunday; a good card from this station showing the national bird. TGWB. 6540kc.. Is also heard In some locations till 4 pm.

Cuba Is heard well over COBC at 10.30 om. COBZ at 10 pm; COCQ is a god one at 9.30 pm; COCX is heard at 7 am, and COHI on most nights through the noise at 10 pm. We tuned a good signal one night from what we think is COKG; In fact, we were sure of It, but the latest Issue of VRC bulletin shows that this station has moved from 8955kc. to 9020kc. This fellow always did Jump around a lot. We would like more rqports on this group If you can hear them.

The South Americans are coming In well at this time of the year, and we have some very fine logs this month from readers at widely separated posts. Venezuela Is heard well through YV5RN. YV6RU and YV5RU are. coming In at 7 am. while at nlvht all are available, with the addition of YVRIU listen about 9 pm, Mr. Moore raises an Interesting point in that the reception of stations on this band at night Is better when there la no moon. We have not heard of this before, and would like to know of other readers' experience In this regard. HCJB Is yood on all frequencies, with the 19m. band showing up at poorer level than the others; that Is our experience at least.. CH615—Is reported at several posts at 9 pm. but not here. CE970 Is heard In the 8 am period on some days, also till 2 om In the afternoon. CE1I80 Is again report.! at 9 am and 9.30 pm, but I cannot find a trace of this one here as yet.

(Continuecl on Next Page)

INTERSBTATi: RECEPTION CONDITIONS

NEW SOUTH WALES: Reception In this Slate Is much Improved. KNBX can be tuned on the 13m. band till 8.30 am. but little can be heard of the BBC at night on this band. The 16m. band Is very good through Ihc early morning hours carrying the Americans: the same applies to the lore- noon and afternoon, while a lull occurs from 6 pm till 9 pm. when signals on that band are as good as ever. 19-metre signals are good In the morning and forenoon, when the usual crop of stations are heard. In the afternoon, conditions are still good. A break occurs at 5 pm till 8 pm, after which the band is us good as ever; very little can be heard after 2 am. however. 20 and 23 metre bands are quite good in the morning end night, while the 25m. band Is very fine at all times. The 30 and 31m, bands are also fine, but the 31m. band has deteriorated a little at night of late; this condition is only temporary.

32 and 33 metres are good In early morning and afternoon, with a good log of stations, especially after 8 pm. 41 and 42m. are, as usual, very fine and the 48 and 40 metre bands command attention, especially from 3 pm till 6 pm. and after 10 pm. SOUTH AUSTRALIA: Our reporters state that little can be heard on 13 metres at night. The 16m. band Is very variable, the best period being between 1 pm and 8 pm.

Other bands are much the same as stated for this location, but, from reports, we think that the lower frequency bands are a little better than Is our experience here.

VICTORIA: Like all the Eastern States, reception is good on the whole, and nothing additional can be said in comment us far as Victoria is concerned.

QUEENSLAND: The same bands are heard In this State with the difference that the bands hold up later than Is our experience. Fine logs are made In this State: reception on the bands over 50 mclrcs li very good Indeed at 10 pm and later.

WESTERN AUSTRALIA: No this State this month.

TASMANIA: Also Stale.

reports from no reports Irom this

NEW ZEALAND; Excellent reception on all bands, the outstanding feature being the ability to tune In the Latin Americana at midday and early afternoon. Otherwise reception Is much the same as we experience hero.

NORTHERN TERRITORY: All bands give their quota of stations both day and night Terrific signals are heard both Irom over, seas and our own services at all times. This Is to be expected, however, as many services are beamed lo this area lor entertainment ol troops.

RADIO AND HOBBIES FOR JUNE, 1945 PAGE THIRTY-FIVE

SHOUT WAVES NEW STATIONS AND VERIFICATIONS I S.-W. NOTES

11 thia was IS220kc. and was si limes afiei > pm. Interfered with by CHTA, Possibly s new service will appear on this frequency. _ SPAIN, A new station using [he oaf

coort signals. These reported by Mr. OllleU. LEYTE. WVLC has also branched out with more new frequencies, 9295HC, Is heard at line level, despite the Morse. carrylUK the "Philippine Hour" formerly carried by VLC6; this transmission 7 pm-8 pm. On TUOIcc. the same call is heard at midnight working KPC ,ind KU5Q. This one Is also a good signal. Also heard on 929bkc. Is the call WVLO at COLOMBIA. "Radio Call** reports the re- -epllon of HJFH on Ae75kc. al 9 15 am and

am in the local language on 9SU2kc. is a Ôcd etiolec of frequency from AUSTRALIA. VI.C3 on na7ltc. Is hea 7 pm, KWIX, 9850l;c,, I KROJ, BlOOkc, all open: nt 1,46 am. the other out

. carrying (he news at ed by "Radio Call" ul a che same frequency. I A. VLWd Is badly inle

;o reports^ XQOY

Some Specials from— |

PRICE'S RADIOI

MEXICO. Frou:

Trolitul Midget Condensers, Double Bearing Type, lOmmtd, 25mmfd, SOmmfd 5/- ea. 25yd. Coils Slipknot Insulation Tape .. 2/10. 2^" Diameter Heavy Wall Bake- lite Tube .. 6d. inch. 465k.c. Air Core Aerial and Ose. Coll Kits .. 10/- SOOmfd. I2v. Electrolytic Con- densers ,. 4/- 3-32 Brown Sheet Bakelite, Slightly Stained .. Per Sq. Ft. 2/6

PRICE S RADIO SERVICE

5 and 6 ANGEL PLACE. SYDNEY

being fairly consistent until 7 i again read at 5 am, WSCO 1 reported of late, although we ca

PASE thirty-six RADIO AND HOBBIES FOR JUNE, 1945

SHORT WAVES

OVERSEAS S.W. STATIONS NOW AUDIBLE

The following stations includes those which have recently been heard in this country, together with others which should become audible during the next few weeks. The

majority of them should be audible on a sensitive receiver.

All flmcs are Australian Eastern Standard Time.

ENGLAND GSA—GOSOkc. 49.59m. London. Heard In

Latin service at 9 am-1.45 pm, and Euro- pean in afternoon period.

GSB—9510kc. 31.55m. London. Heard well in OP at 2 pm llll night.

GSC—9580kc. 31.32m. London. Pine signal In QP service In forenoon, heard also from 4 pm.

OSD—1 l"501:c. 25.53m. London. Another good one In afternoon. like a local-

GSE—11800kc. 25.30m. London. Heard In OP at 1 pm, fair only.

GSP—15140kc. 19.82m. London. Best heard from 8 pm In GP service, but on from 3.46 pm.

G3G—17"90kc. IS.aem. London. Eastern service at 9 pm, fair level.

G3H—2I470k0. 13.97m. London, Still operates 9,45 pm-1,15 am, poor signal at this location.

GS1—I5260kc. 19.66m. London. Good one to Africa at 4 am-7 am. Heard at 9 pm also.

GSL—61l0kc. 49.10m. London. Good opening NA service 7 15 am. European at other times.

GSN—11820kc. 35.38m. London. Used In Pacific for New Zealand 3 pm-8 pm.

GSO—15180kc. 19.76m. London. Mainly In GP service In evening.

GSP—15310kc. 19.60m. London. Pine signal In GP service from 9 pm. Best on this band.

GSU—7260kc. 41.32ra. London. Heard also at opening of N. American 7.15 am. fair signal, African also till 7 am.

GSV—nsiOkc. 10.84m. London. Pair at times In OF service at night.

GSW—7230kc. 41.49, London. Excellent signal In afternoon In GP service, beamed to this area. Also In European In morning. GRB—6010kc. 49.92m. London. Used In Latin In forenoon, European In afternoon, good signal 4 pm.

GRC—2880kc. 104.2m. London. No reports lor this one. N. American 10 am-2.45 pm.

ORD—15450kc. 19.42m. London. Used In GP service at 1,30 am. only weak here.

ORE—15390kc. 19.90m. London. No schedule for this outlet. Heard at times at 11 pm.

GRP—12095kc. 24.B0m. London. Good signal GP service at 7 pm. Best at this time.

ORQ—11680kc. 25.68m. London. Heard at 4 pm In GP service. Not as good as has been heard.

GRH—9825kc. 30.53m. London. Best at 7 am In African and 7.15 am opening on N. American. Heard well at 1.30 pm In same service.

GRI—9410kc. 31.88m. London. Used In Latin service In forenoon, also In European service from 1.30 am.

GRJ—7320kc. 40.98m. London. Another In N. American till 1.30 pm. Heard In OF till 7 am.

GRK—7185kc. 41.76m. London. Latin In forenoon good signal, European In afternoon, fair level.

GRM—7I20kc. 42.13m. London. Best In Paci- fic service at 3 pm-6 pm. Good at times In Eastern service at 9 pm.

GRN—6195kc. 48.43m. London. Only In Euro- pean service at 5 pm. AEP service later at 7 pm.

GRO—6180kc. 48.54m. London. Heard In Home service at 4 pm. European service In forenoon. GRP—n870kc. 16.1901. London. Used to Africa at 1.45 am. poor here. ORQ—18025kc. lQ.04m. London. Latin mainly at 1.30 am. No other schedule known.

GRR.—6070kc. 49.42m, London. Latin In forenoon and European at 4 pm. GRS—7065kc. 42.46m. London. Fine In GF

at 2 pm oeamed to Australia. GRT—7150kc. 41.96m. London. Heard well in

Latin In forenoon, European In afternoon. GRU—9910kc. 30.2flm. London. Pine signal In Latin In forenoon. GP service at 8 pm and 8 am.

GRV—12040kc. 24.92m. London. Fades In with Pacific service from 3 pm. good from 4.30 pm.

GRW—6150kc. 48.78m. London. Used to N.

America 12.15 pm-1.30 pm., OP service In afternoon,

ORX—9690kc. 30.96m. London. Good one In Pacific service at 3 pm-7 pm. Also heard In Eastern service at 2 am.

ORY—eeookc. 31.35ra. London. Pine signal In GP service at 3 pm, also In African service at 3.15-7 am.

GVO—I80807;c. 16.59m. London. Heard In Persian at 8.30 pm, then In OP service.

OVP—177001:c. I6.95m. London, This outlet heard to Near East at 8.45 pm. GVQ—17730kc, 16.92m. London, Weak at

most times In GP service at 9.30 pm. OVR—21675kc. 13.84m. London. GP service

station at 7 pm. Hardly audible now. GVU—maOfcc. 25.47m. London. Another In

Latin In forenoon. Heard In afternoon also. GVV—in30kc. 25.58m. London. Good at night In European service. GVW—inOOkc. 25,64m. London. Good one In

African service at 1 30 ani-7 am. OVX—ll930kc. 25.15m. London. Pine In OF

In afternoon at 4 pm. GVV—11955kc. 25.09m. London. This one

also heard In afternoon at fine level. GVZ—964okc. 31.12m, London. Used In Paci-

fic service for NZ at 3 pm-7 pm. OWA—6125kc. 48.98m. London, European ser-

vice at 6 pm. good signal. OWB—9530kc. 31.41m. London. Another In

European service at 3.30 pm. GWC—15070kc. 19.91m. London. Heard at

line level at 8 pm In English by Rado In European service.

QWD—15420kc. 19.46m. London, Pacific service at 5.3 pm. fair. Latin at 1.30 am In news.

OWE—16435ko. 19,44m. London, Good In GP service In afternoon.

GWP—9490kc. 31.61m, London. In the clear now In afternoon In European service. Good signal.

QWH—llSOOkc. 25.42m. London. A further European service station at 6,3 pm, heard through the evening.

G —7250kc. 41.38m. London. Heard In Ttln In forenoon, and In European at 5.45 pm.

GWJ—9530kc. 31.48m. London. Still heard In European service at 4 pm. good level.

GWK—61 GUkc. 48.66m. London. Heard at same time In same service. Good also.

OWL—7205kc. 41.64m. London. Another heard at same time In this service.

OWM—6090kc. 49.26m. London. Listen for this outlet at 4 pm In European.

GWN—7280kc. 41.21m. London. Latin In forenoon. OP at 2 pm.

GWO—9625kc. 31.nm. London. SHU heard In GF service In afternoon at 3 o'clock.

GWP—9660kc. 31.06m. London. European service In evening, but Interference bad on this spot.

GWQ—11840kc. 25,36m, London. European service m afternoon with a fair signal at times.

QWR—15300kc. 19.61m. London. Heard In GP service at a pm. fair only,

OWS—6236kc, 49.71m. London. Operates In EUTopean service at 3 pm and In forenoon.

NORTH WBOS—ISQIOkc. 19.72m. Boston. Opens with

a fine signal to AEP at 9 pm. WBOS—9897kc. 30.31m. Boston. Closes at

good level at 7.45 am, good earlier at 6,30 am,

WCBN—I1145kc. 16,92m. New York. Good one In early morning till 9.15 am. WCRC—11826kc. 25.37m. New York. Good signal In APRS show at 9 pm.

WCRC—9590kc. 31.30m. New York. This one heard well at 0.30 pm. Heard later also.

WGFA—11847kc, 25,33m. Schenectady. This outiet carries APRS show at 10 pm.

WGEA—7000fcc. 42.80m. Schenectady. Closes In English at 6pm.

WGEO—9530kc. 31,48m. Schenectady. Closes In Latin at 2 pm, heard also 7.15 am,

WLWK—15250kc. 19.67m. Cincinnati. Heard 8 am-10.15 am fair level.

WLWK—imokc. 25.02m. Cincinnati. This one very good at 9.30 pm. Operates 8.30 pm-7.30 am.

WLWK—6880kc. 49.34m. Cincinnati. Sched- uled 10.30 am-3.I5 pm, will be beard at close of service. WLWL—17955kc, 16.71m. Cincinnati. Sched- uled Mid.-4.30 am, heard early part of service.

WLWL—16230kc. 19.70m. Cincinnati, Sched- ule Mld.-1.45 am, 4.45 nm-9.1S am. 8.30 pm-11.45 pm. Heard In latter service. WLWL—16200kc. 19.72m. Cincinnati, Oper- ates 2 am-4.30 am, fair at end of transmission.

WLWL—13022kc, 33.96m. Cincinnati. Heard well between 4.45 am and 9 am and again between 8.30 pm-11.45 pm.

WLWL—9897kc. 30,31m. Cincinnati. Good one heard for most of service at 9.15 am- 1 pm. WLWL—7575kc. 39.00m. Cincinnati. Heard between 5.30-9 urn and 9.15 am-I pm. WLWC—naookc. I6.85m. Cincinnati. Oper- ates from 8 am-8.45 am. heard locally.

WLWC—15250kc. 19.07m, Cincinnati Heard 10.30 pm-5.45 am. Good signal at times.

WLWC—9590kc. 3l.28m. Cincinnati. Oper- ates 6 um-7.45 am, 9 am-3.15 pm, will be heard throughout soon, WLWR—9750kc. 30.77m, Cincinnati. Heard during period 9 pm-1 pm.

WLWS—18180kc. 16.50m, Cincinnati. Heard prior to 5.30 am and from 10.45 pm.

WLWS—IS300kc. 19.72m. Cincinnati. Sched- uled 8 am-10.15 am, 10.45 pm-13.15 am, fair at times. WLWS—11710kc. 25.62m. Cincinnati. Good one between 8 am and 12.30 pm.

WLWS—7B40ko. 38.28m. Cincinnati. Heard In Latin at good level at 8.45 pm.

WLWS—«370kc. 47.10m. Cincinnati. Another good one heard from 8,45 pm-10.30 pm.

WNRA—9856kc. 30.44m. New York. Strong one at 9 pm In V of America opening at 7 pm, KWIX Interferes later.

WNR1—ISOSOkc. 22.91m. New York. Heard well at 9 pm.

WNRI—7563kc. 39.66m. New York. This outlet reported as strong at 0 pm.

WNRX—OlOOkc. 49,18m. New York. Pair level at some posts at 3 pm.

WOOC—7e20kc. 38.36m. New York. Heard opening at 7.30 am, fair,

WOOW—11870kc. 25,27m. New York. Also heard at same time In same service.

WRUL—I I730kc. 25.56m. New York. Voice of America at 9 am.

WRUW—9700kc. 30.93m. Boston. At fair level till 4 pm. WJQ—lOOlOkc. 29.97m. New York. Contacts NCB In Belgium at 6.60 nm.

CBPX—9030kc. 31.15m. Montreal. Heard with fine signal at 10.30 pm,

CBRX—61 coke. 48.70m. Vancouver. Reported at 10.30 pm on this frequency again.

CPRX—6070kc. 49,42m. Toronto. Good at some locations dl 9 pm. with good slg, but QRM'd bv Moscow at 9.45 pm.

CHMD—304Okc. 31.12m. Snckvllle. Reported from NZ at 4.30 am. CHTA—15220kc. 19.71m. Snckvllle. Operates 8.35 pm-11.5 pm. 11.45pm-5.15 am. Heard here at 8.40 pm.

CKXA—moskc. 35.03m. Sackvllle. Sched- uled 0.10 am-7.35 nm. XEBR—11826kc. 26.37m. Mexico. Good one at 13.45 am, call In English at 12.40 am.

XEQQ—9680kc. 30,99m. Mexico. Good one on Sunday at until 4.15 pm. XERQ—9616kc. 31.21m. Mexico. Reported from NZ on 9580kc. at 2 pm. XETT—0557kc, 31.39m. Mexico. This one weak at 8 am. Should be heard till 2 pm Sunday. XEWW—9S03kc. 31.57m. Mexico. Heard weU In afternoon and from 11.30 pm.

XEYU—B600kc, 31,25m. Mexico. Heard In NZ at 3 pm. but GRY would be too much for It here.

)

HP5A—11700kc. 35,64m. ranama. Tms one fair at 9 am, some posts at 11 am.

HP5B—6030kc. 49.73m. Panama. Heard Irregu- larly at 10.30 pm. fair In Q.

HP5G—inSOkc, 25.47m. Panama. This one fair, closing at 2 pm, also on at 11 am.

1ADIO AND HOBBIES FOR JUNE, 1945 PAGE THIRTY-SEVEN

SHORT WAVES Johannesburg J—SMSkc, SI.Mm, South Africa. Capetown 3—ZRL, BMIk'c. 31.37m South

Radio National Espana—IMlTkc. 19.22m. ZNB—SSOOkc. 50.85m. Mafeking. This

OOBC—83?0kc. 'w 00m I at 10 10 pm. COBQ—9220kc. 32.54m. SUV—lOOSOkc, 29.84m. Cairo. Thla ona good signal at 4 am. SUX—7a«51cc. 35.15m. Cairo. Heard well dally

Australia at s pm. CSW6—11040kc. 27.17m. Lisbon, f as at one time In transmission al Ponta Delaga—7020kc. 42.74m. A2

SOUTH AMERICA

-■4»«01;c. "sLTIm" Caracas, Another PZI—9440kc. 31.78m. Brasznvllle. This <

AUSTRALIA AND OCEANIA

MISCELLANEOUS Radio Belgrade—9605kc. 31.57m. Togoslavia. Has been Intercepted al. I.IS am-3.S0 am,

AUSTRALIAN SCHEDULES

Rome—(Xl20Kc 49.83m. Italy, Good c

INDIA AND ASIA

d In Weiuneton a Iransmllters are The calls and fteoaenoles designated are ZLl 8«aQko.. ZL2, 9S4«kc.. ZU ll78«ko.. ZL4 t52B0ko. Programmes will he directed to the Pacific Area and later to the West Coaat of O.3.A.. fallowed by an even greater coverage. This Radio Centra will bring New Zealand in line with Australia, south Africa and Canada, who are operating such services.

RADIO AND HOBBIES FOR JUNE, 1945

RECORD RtVftW

This month we list the contents of the May-June supplement, together with the current popular releases. Selected records from both sources ore discussed by our contributor, and further reyiews will be published in our June issue.

of greel fullness and Quality, and she r boll) these numbers with an abundance understanding and confidence. The recor< ' Other Recordings

5 MATHEWS. Pia no. Ilpcorclcn Aiiuirirun i

By Audisc

BECOME AN ARTIST

-QUICKLY ffk LET B ROD IE MACK TEACH

YOU AT HOME YY AT lasl you are able lo leant all branches of ( < rj 4 f ' ait under the superviBiou of this fnmouB A \ •' / k "l AustraliaH artinl. Amazin; short-cut me thud I \/ J / // simpllfles art. You can learn at home. V r f J Jf MAKE MONEY^ IN YOUR SPARE /CYl

HOW TO BE AN ARTIST IS FREE I "^fvf.r brfnr, baa a booh «l ttalo nature been ofTered

| —how lo cartoon, the secret el illnstTaUng^ etc. Fill i What this FREE Book is about

J 1 TEAR THIS OUT ~ POST NOW! • I The Brodie Alack riorreapoiidenee Arl School, I l>csh Wl, it Clarence ftlreei. Sydney, N.N W

S The BRODIE MACK M'urrespondcnce Art School. 2 Desk 99. 24 Clarence St.. f t Sydney. N.S.VV.

RADIO AND HOBBIES FOR JUNE, 1945 PAOE THIRTY-NINE

WORKSHOP '

IA SOLID MODEL OF THE "AQUITANIA" ■

3he dquitania

v4<-ir- '--I

.i-^l

i r-v

sv 7^1

:.eui—,■

A fitting comportton for the Queen Mory described in the April issue, it this solid model of the four-funnel Aquitonio. Aut- trolions hod opportunity to tee this grcot ship in our own ports when, earlier in the war, it wot used to transport Australion troops overseas. By W. G. Nichols

I details such as winches, davits and railings are not essential for the model to give a good portrayal of the original. The plans for the Aqnltanla which accompany this article are to the scale of one Inch equals a hundred feet. Although the model 18 thus nine inches long, the dimensions can be rescaled by the builder if he desires to build something larger than the one described. The material list included with the article will prove helpful, bnt remember that the list is for a nine-Inch model only. The model is constructed on the familiar "bread and butter" principle, balsa wood of various thlcli- nesses forming the layers. Make a full-size cardboard pattern of piece "A." This can be done accurately with ruler and compass. The bow (liln. long) is lln. wide and shaped by the two arcs of 41n. radius. The centre section is an oblong lln. by 51n. and a trapezium of 1 7-8ln. altitude, with bases of lin and Jin. respectively A semi-circle of 3-8In. radius forma the stern. Cut all wood to the shape and size specified. Then usln» the cardboard pattern, shape piece "A" into a blank; PASE FORTV

carve the stem e shown. Cut piece bottom and sides black, but leave the upper side unpalnted. Any dimensions not shown are of minor importance and can be scaled directly from the drawings. Details for making the various units of the superstructure ore shown in the second group of drawings "C" to "P." Pieces "C to "I" are all based on oblongs of Identical width and varying lengths and are not difficult to measure. Pieces "J" to "O." however, are based on the trapezium mentioned in making the pattern, and It is. therefore, impracticable to give dimensions other than the altitudes in accurately measurable terms. Slmplv slip each piece under the cardboard at the proper place and cut it to match the pattern. Pieces "J." "L," and "N." must then have l-8in. removed from each side. Locale points X and Y on all these pieces. These points are all on the centre line; the olans give the dis- tances from the end of each piece. Making all points X coincide, glue "D" to "C." "E" to "D"' and so ou. Then with all oolnts Y coinciding, glue "J" to O." "K" to '"J," and so on. By passing a pin through points X and

another pin through points Y. slacking is quite simple. Ti> piece "T,- adc pieces "H." "S." " T." and "P" In the order they appear .:i tr.e plan, and to the top of "P." add 'Q'- as Indicated by dotted lines. Make thirty-two lifeboats each (-]61n. wide, l-16!n. deep and lin. long. These can be cut from the 21n. balsa strip (see the material list), or they can be made from lengths of wooden matches. Each lifeboat should be shaped at each end and glued in the (Continued on Next Page)

MATERIAL LIST (Balsa Wood Preferable)

RADIO AND HOBBIES FOR JUNE, IMS

RECORD REVIEW THIS MONTH'S RECORDINGS

BRADUSY KINCAID, Slnglna vl(h Ouitar' "3om_«hoJy'« WaU'ng lor Von." "The Blind uin. Segal Zonophona, 021Q13. Popular Releases LOD TOPPANO. Piano Accordion Soldi- ••PANORAMA" and "P1LLIN' IN TIME," hold ny Lou Toppano. Regal Zonophone, 021U19

"MELANCHOLY SERENADE" '(Iaiu Top pa no i and "WALTZING MATILDA" I Cowan). Regal Zonophone, 034920. LOO AND BNZO TOPPAND. Plane Accordion Duets: "CaRIOCA" (Tonmans. arr. Lou Top- pano) and "BHAPSody in BLUE" (aershwin. arr. Lou Toppano). Regal Zonophone. 034931. When a sood piano accordionist "goes to

BIS MASTER'S VOICE OLENN MILLBK AND ORCH.: "The ot « Starry Night"—P.T. (V.C.) "Rh In Blue"—P.T. |N.Vil, EA3JJ2. ' JOE LOSS AND ORCH.: "If You Ei ,v-c-'. " (Too-Ra-L

QBOROE TBEVARE AND 1 "Don't Fence Me In"—P.T. Qoea that song Again"—ft. qeoroe trevare AND I "Just Like a Lavely Dream "aome thing's the Matter » (V.O.i. 034919. QEOROE TREVARE AND 1 "You're Charming, You're La

SOUD MODEL OF THE AQU1TAM1A

compares favoraWy with anyone^ in the world, noticed, Lou is something of a composer and arranger. For sheer technical ability J nave heard nothing belter, and 11 is hard to choose between the Items, for they each nave^lheir own special features. __ "Waltzing series of variations which are ^rlillantlr performed. 1 find nothing to chouse between

of most pleating quality; simple! sweet, an with no unnecessary frills. Nice quid dreui

(Continued fPom I positions Icdlcated on the plan view. Tiie twenty-four boat8 glued to piece "I" are placed 12 on each aide and spaced three to the Inch, Thirty-six small ventilators are made by bending iln, pins, so that the head is at right angles and very close to the pin. The plan shows how the ventilators are grouped around the roar funnels and at the sides of pieces "R," "S." and "T." The pins should be pushed in till the top of the pin is about 3-lGin above the level of the deck. When assembled, paint the entire unit (except the underside) white, giving a second roat if necessary. Make the funnels bv sandpapevlriK a l-8in. bv Jin. stick to an oial shape Cut the four funnels each S-8in. trim- ming the underside to the required angle. Paint the top half of each funnel black and the bottom half red When dry. attach the funnels to the superstructure by means of a Jin headless pin driven through the centre of each funnel and Into the superstructure. Glue the soperstrrcture to the imll making certain that the sides mateh.

above deck level. ■ Finally touch the faees of the heads of all Dim used bs ventilators with red nnlnt and your model is eom- pleted. RADIO AND HOBBIES FOR JUNE, 1945 PAGE FORTY-ONE

BOOK REVIEW

Technical Book Review

The technical Editor reviews yet another batch of technical books for "Radio & Hobbies" readers. If you wish to purchase any one of them, write direct to one or other of the

booksellers advertising in our columns. "l.A|IRELESS COILS, CHOKES AND and their 1944 Handbook is no excep-

VV TRANSFORMERS." By F. J. tion to the rule. It will appeal to all Camm (Editor, "Practical Wireless"), concerned in the maintenance of air- Published by George Newnes, sixth craft, as well as to others whose in- edition; hard cloth cover. 180 pages, terest is more casual. Australian price, 7/3 (approx.), postage 4d.

The first two chapters deal with the fundamentals of flight, after which

Although all radio textbooks make there are chapters on aircraft struc- passing mention of coils and chokes, tures, gliders and sailplanes and there arei few, if any, which have anything comparable to the amount of in-

lighter-than-air craft. Chapters 6 to 9 inclusive cover air-

formation on the subject given in this screws, motors, &c., with subsequent book by P. J. Camm. Its popularity special sections on stratosphere flight, is indicated by the fact that six edi- aircraft instruments and modern de- tions have been issued since 1937. veiopments, The book contains a

The preliminary chapters cover the variety of detailed plane and corn- basic principles, after which there is ponent drawings, together with sundry separate discussion of coil construe- interesting photographs, tion, simple coils, band-pass, screened, ★ ★ ★ switched coils, ganging, &c. "EXPLOSIVES," By Dr. John Read

High frequency and low frequency —one of the "Pelican" series. Paper chokes are under separate headings, likewise audio and power transformers. At the back of the book are sundry

cover, 160 pages. Australian price, 1/3 (approx.), postage 3d.

To begin his discourse, the author data, lists, tables, &c., likely to be of of this book introduces the reader to

suggestions for the mechanically minded handyman—workshop hints, handy gadgets, plating, &c.—available now in an attractive cloth binding.

★ ★ ★ "PAINTING, FURNITURE FINISH-

ING AND REPAIRING." Published by the Popular Mechanics Company. Hard cloth cover, 96 pages. Australian price, 8/6 (approx.), postage,5d,

A book which will be welcomed by the home carpenter. It is a collection of typical "Popular Mechanics" articles covering painting, staining, polishing, and hints on the restoration of used and antique furniture. Freely illustrated with both line and half-tone pictures.

★ ★ ★ "CONCRETE HANDBOOK." Pub-

lished by "Popular Mechanics" Press. Hard cloth cover, 96 pages. Australian price, 8/6 (approx.), postage 5d.

There, is something very satisfying about well-executed concrete work, and this book is a source of hints and ideas for the handyman with this particular interest. Some suggestions are purely ornamental, others utilitarian: and the requirements of rural dwellers are not overlooked. ■

(All books on. this page were supplied for review by Angus ■and Robert- son Ltd., 89 Castlereagh St., Sydney.)

use to the reader. the general subject of chemistry, and The book has a typically English then explains just what an explosive is.

"flavor," but will make interesting In succeeding chapters he traces the reading for all enthusiasts who take invention and development of explosives this coil business seriously. right up to the present types manu-

★ * factured from cotton or coal. The book "FLIGHT HANDBOOK," Fourth concludes with a chapter of "frag-

edition, 1944. Hard cloth cover, 212 ments' explaining special aspects of pages. Australian price, 12/- (approx.), t'16 subject. postage 4d. ' ' An interesting little book for the

The quality of "Plight" publications Popular science enUiusiast. Is well known to aircraft enthusiasts, *

Announcing —

training courses in

PLASTICS

DO YOU rvallse the part Plastics are now playing in industry and domestic life? Look around and note the hundreds of Plastic articles that come into view—then learn of the tremendous volume of Plastics that are used in practically every phase of industry.

THE SATES of this vast and revolutionary field of Plastics are now open to YOU! Here is the awaited opportunity of acquiring a thorough training in basic principles—a course of study that will equip you with practical technical knowledge of the materials, manufacturing processes and appli- tions of Plastics.

THE PLASTICS Basic Knowledge Course, written and conducted by experienced Plastics engineers and chemists, wilt help to qualify you to become a Plastics technician. Ambitious men and women, eager to win for themselves a prosperous future in Plastics, and who âre prepared to devote a few hours weekly to home study, are invited to send for details, Dept. N.

BOX 4677. G.P.O., SYDNEY

A DIVISION OF PLASTICS TECHNOLOGICAL CENTRE

★ ★ ★ "POPULAR MECHANICS SHOP

NOTES," 1943. Published by the Popular Mechanics Co. Hard cloth cover. Australian price, 10/6 (approx.), postage 6d.

The style of the workshop features in "Popular Mechanics" magazine needs no introduction, being -well-known for their attractive combination of line drawings and half-tone illustrations.

Here are 200-odd pages of idteas and

RADIOTRON PHOTOTUBES |

SEVERAL types of phototubes are I available in limited quantities |

from Amalgamated Wireless (A1 asia) < Limited (Commercial Engineering De- partment). These include types 920 twin gas tube, 921 gas tube cartridge type, 922 vacuum tube cartridge type 923 gas tube, 925 vacuum tube for re- lay operation and 926 vacuum tube cartridge type particularly Intended for colorlmetry. -

Copies of the Radiotron phototube .chart are available free on application (3d. postage), from Amalgamated Wire- less Valve Company Pty. Llmyted, Box 25I6BB. GPO. Sydney.

PULSE-TIME MODULATION Development oi a system of

pulse-time modulation applicable to wire and radio, including broadcasting and television sound channels, was disclosed at a meeting of the Insti- tute of Radio Engineers by E. Labin and E. M. Deloraine, of Federal Tele- phone and Radicr Laboratories, associate of the International Telephone and Telegraph Corporation. It consists essentially in transmitting intelligence by pulses ot constant amplitude and duration.

Instantaneous amplitude of voice is translated into a variation of time in- tervals of successive pulses, the rate of variation corresponding to instantaneous frequency of signal. Its main advantages include simplification derived from the use ot more rugged repeaters capable of operating on trigger action, and thereby reducing the usual re- requirements tor stability of distortion and noise.

Distortions introduced in different repeaters are not cumulative. De- velopment work started in 1937 on the basis that with modern transmission technique a much wider band-width per channel is available than is strictly required by the elements of most sig-

nals transmitted. Compared with amplitude and frequency modulations, pulse-time modulation appears promis- ing for multi-channel, coaxial cable, telephone, telegraph and facsimile transmission systems, also point-to- point radio and ultra-high frequency broadcasting and television sound channels.

GUESSWORK usually involved in locating broken wires under the

insulation ot electrical extension cords and wires is eliminated when the electronic tester developed by the Consoli- dated Vultee Aircraft Corporation is used. Iir the unit, one electronic tube is connected as a self-excited oscillator operating on about 400 cycles frequency. The oscillator output is applied to the cord. A small amount ot signal energy is picked off the cord by the metal ring through which the cord is passed. Fed to a high-gain amplifier, signal amplitude is sufficiently increased to operate the output meter. When the break in the conductor passes through the ring, the sudden change in meter deflection instantaneously indicates the broken spot.

PAGE FORTY-TWO RADIO AND HOBBIES FOR JUNE, 1945

UNDER THE PERSONAL SUPERVISION OF THE TECHNICAL EDITOR J.L., of Hobart, asks •whether it would be

possible to connect a number of torch cell batteries In series to substitute for high- tension B-batteries.

A.; Actually, torch cells could be connected in this way, but to obtain the usual 90 or [ 135 volts would be a tedious and rather ex-

t pensive proposition. Each cell delivers only 1 1.5 volts, so that no fewer than 60 would be ' required for a 90-volt supply, or 90 for a ; 135-volt supply. The life would probably be 1 considerably less than obtained with regular Isuperdyne batteries.

E.P., of Preston, Victoria, sends In his year's subscription to "Radio and Hobbles," |nd asks about copper oxide rectifiers, i A.: Many thanks for your subscription, kdiich has duly been recorded. We have jiever described the manufacture of copper ixide rectifiers for the home-builder, but, in iny case, It would be a difficult matter io even approach the characteristics of commercial types. Por general technical Infor- nation, we suggest you write to the Ampllon Hy., Ltd., 36 Parramatta-road, Camperdown.

J.P. (Sydney) advises that he has managed \o clear up a difficulty In his receiver, following advice through our Shilling Query lervice. A.: Many rhanks. J.P.. for your letter, and ve are glad to know that our advice proved o helpful.

W.E.H.. of Brisbane, writes to say that he las completed the pendulum type electric clock, which is operating satisfactorily. He

now suggests that we describe a more advanced type, utilising the synchronome principle.

A.: Many thanks for your letter. W.E.H.. and for the report on the electric clock. The synchronome type was well known to us at the time, but the design published was ready to hand and had much to commend it. We are doubtful whether we will be able to give any further space to this subject tor the time being. Your suggestion for bound copies of "Radio and Hobbies" is a good one, but completely impracticable at the moment, as we have no stocks of back Issues available for binding. Nevertheless, many of our readers have the magazine bound pri- vately, for convenience and permanence.

L.M.T., of Lavender Bay. N.S.W., writes in appreciation of our past tuner, tone control and amplifier circuits, and suggests that we should go ahead and combine three such units into a Deluxe Radiogram. A,; We have received several suggestions along this line but have not complied, since we do not consider the time opportune. While a few readers may have the parts on hand to duplicate our design, the effect of the article might only be to promote a lot of unnecessary sales for parts which should go for more urgent requirements. However, do not despair, as the big set fan will have his day Immediately conditions Im- prove.

R.M., of Kingsford, N.S.W, asks several questions, which are answered in order: A.; (l) For the "Model Engineer" series,

we suggest you inquire at Walther and' Ste- venson, 395 Oeorge-staeet, Sydney, or at one or other of the technical booksellers advertising in "Radio and Hobbies." The same firms may be able to supply the other book you require but. if it Is now out of print, your only chance would be to advertise for it. (2) Articles on trick photography have been published from time to time In photographic magazines, but we have never come across a book dealing specifically with the subject. However, you can inquire at the booksellers for this one, too. In prewar days, dry ice was used occasionally as packing for ice cream in small quantities, and this was probably the source of dry ice for use in simple reaction-propelled toys. However, we have not seen anything of them of late, so that the idea may have to be shelved for the Ume being.

S.J.G. (Caulfield, Victoria) sends In his sub scriptlon to "Radio & Hobbies," and men- tions that he is experiencing some trouble with "Tiny Tim Two" on the shortwave band.

A.; Many thanks, S.J.G., for your subscription. which has duly been attended to From what you say, It seems likely that the Instability you mention Is In the nature of an audio howl, and only remotely related to the adjustment of the reaction coi'l. Try reducing the value of the detector grid resistor to 0.5 meg., instead of the 1.0 meg. resistor speci-

fied. Also "make sure that the plate wiring of the output valve is well clear of the tuning and detector grid circuit.

J.M. (Leichhardt) sends in his subscription for the ensuing 12 months, and comments on the multi-vibrator circuit described in "Radio & Hobbies" for February last.

A.; Many thanks, J.M., for your subscription, and also for the report on the two multi- vibrator circuits. Glad to know that they have turned out 8(4 successful.

R.K. (Lonwood, South Australia) sends in his subscription to "Radio & Hobbies." and tells of his experiments with small one and two-valve receivers. He has done much experimenting with broadcast colls wound on iron cores, and finds them very efficient.

A.: Many thanks, R.K., for your sub., which has duly been attended to. We read with interest your remarks about the iron-cored coils, and will be pleased to examine a more detailed report when you have an opportunity to prepare it.

QUERY SERVICES ORDINARY technical queriet will be |

answered on this paqe in strict rota- tion. Readers who desire answer by mail should enclose a postal note or stamps to the value of one shilling. We are short of staff, but will do our best to answer as promptly as possible. Make your letter clear and to. the point and do not ask us to draw special circuits, as fhis is impossible at tha

moment.

F.A.W. (Bendigo, Victoria) advises re a change of address, and also asks for the operating conditions of type EL3NG valves for push-pull with 275 volts on the plates.

A.: The data on hand does not give special operating conditions for EL3NG valves in push-pull, but the following suggestion should not be far out: Plate and screen voltage, 275; Cathode Bias resistor, 100 ohms; Plate to plate load, 14,000 ohms. You could expect a total current drain of between 70 and 80 milliamps, and a power output of nine watts.

H.H.C. (Milton, Queensland) asks whether It is possible to operate a 250 volt Neon lamp from a 40O volt supply. A.; Without knowing further details. It is difficult to say Just how much current your Neon lamp would draw. It may be anything from four or five miili-amps up, depending on the wattage rating. Your best plan would be to find out who is a manufacturer or agent in this country, and write to them for further particulars. Operation from 400 volts should certainly be possible, but the amount of series resistance will depend entirely on the current.

W.N. (Ineerim East, Victoria) sends in an account of his experiments with wind charg ers, and also a couple of photographs.

A.: Many thanks, W.N., for the interest you show In "Radio & Hobbles." and for taking the trouble to write out a report. The photographs and your letter have been filed tor future reference.

G.S.R. (Burwood, Victoria) reports having built up a couple of our small sets, and is now anxious to construct ' the "Dual Wave Little General" from parts on hand.

A.: Many thanks for your report on the small sets, and glad to note that they are operating satisfactorily. The "Dual Wave Little Gen- eral" could be constructed using ELS NO in the output stage, but it would be necessary to halve the value of the back-bias resistor, that is, from 4Q0 to 200 ohms. We doubt very much If you would be able to obtain a suitable cabinet for this receiver under present conditions.

J. McD. (Melbourne, Victoria) reports having built up our "Sergeant-Major" circuit from all kinds of odd bits and pieces. His only tools were pliers, screwdriver, hacksaw blade and hammer, with a 61n. copper nail serving as soldering Iron. Chassis was cut from an old aluminium saucepan, and a cabinet from scrap wood V?as covered with old shirting material, painted to iook like grey

leather. Excellent results are obtained on a collapsible curtain rod aerial or an outside aerial—this despfte the fact that the receiver is operated only a quarter of a mile from SAW's aerial.

A.; Many thanks, J. McD., for your report on this receiver, and glad to note that It has turned out so well, despite the varied nature of the components,

F.P. (MacksvlUe) has recently acquired a commercial dual-wave receiver, but the performance is apparently mediocre.

A.: We do not know the particular make very well, so that it is rather difficult to comment on the results you are obtaining. However, we would hesitate to blame the EK2 valve, since it has proved quite effective in this type of receiver. We would not expect any radically different results with the 6J8-G. Your best plan would be to have the align- ment checked, If you cannot do the Job yourself. J

J.F.M, (Goulburn) Is apparently anxious to make a study of efficiency charts for airfoil sections similar to those published in "R & H" for July, 1942.

A.: We have no literature available for distribution giving the information you desire, but suggest that your best plan would be to write to the Public Library. Macquarle-street, Sydney. Glad to know that you enjoy reading "R & H" from month to month.

J.F.S. (Cbarleville, Q.) writes tq say that he has had a similar experience to a correspondent in Melbourne, who heard strange shortwave signals on his crystal set. In the ease of J.F.S., the signals are apparently an aircraft beacon. He also asks one or two other questions.

A.: Many thanks, J.F.S., for your letter which was read with interest. The volite? across the field coil of an Ampllon N25 loM,^ ipeaker will depend entirely on the amojjfftt of current you are drawing through it. A normal current figure would be from 50 to 60 milliamps. which would result in a d-c voltage of from 125 to 150 volts across the loud-speaker terminals. We are well aware that not many circuits for d-c power mains are given In "R «Sc H," but there are various reasons for this. The most obvious one at the moment is the almost complete absence of rectifiers and power valves suitable for use on the d-c power mains.

M.D. (Kurri Kurri) writes In appreciation of r <K H," but suggests that we should occasionally describe the construction of cabinet to house the various receivers.

A.: Many thanks for your letter, M.D. but as you suggest, there are various reasons why the idea is not entirely practicable. In war time, the most obvious one, of course, Is the lack of suitable plywood.

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RADIO AND HOBBIES FOR JUNE, IV45 PAGE FORTY-THREE

ANSWERS

SHORT-WAVE REPORTS

K. Jonrs (Forbes. NSW): Pleased to hear you are still listening, good luck at your new job.

J. Meiers (Box Hill. Vic.): Always glad to welcome a new correspondent. \Vlll drop you a line soon.

D. G. Sanderson (Brisbane, Q): The Cen- tral Americans are coming In nicely now. pleased you are hearing them.

J. J. Lee (Darwin. NT): Thanks for the log; It was a bit late for our last Issue.

N. Handson (Merrylamls. NSW): Hope that ere this you have managed to hear a few of the morning stations.

A. E. Moore (New Farm, Q): Good luck on the new ones and the veries. You are having a good year.

G. Petersen (Australia): We replied to you. hope all the points were clear to you. Good luck.

Dr. K. B. Gaden (KUIamey, Q): Thanks for the letter. 1 agree with you on all points, but am hoping for the best.

Miss D. Sanderson (Malvern. Vic.); Both letters much appreciated. Hope all those veries come to light. . .

G. Smart (PI. Cook. Vic.): Will look Into the matter for you. Thanks for the South African news.

G. Gates (Stawell. Vic.): Thanks for your letter also. Will be interested In your logs.

A. Kew (Bankstown. NSW): Hope vou received our letter. Good work on the letter from the BBC. They are always glad to gel reports.

It. Maddeford (Galley, NSW); Looking forward to a bigger report from your post.

N. Simons (Mortdaie. NSW): Another new one from the same dlsglct. Keep at It and you will find more stations.

WANTED TO BUY, SELL OR EXCHANGE Readers wishing to buy, sell or eiehango goods are invited to insert an advertisemant in this column. The cost is 9d per line; minimum charge 2/3. Advertisements (or next issue must reach our office by Saturday, June 9, 1945.

/ANTED one 3-gang H Condenser. Mr. H. Crossley. Wellington Point, <)Id.

Mr ANTED back numbers R. & H.. Vol. 1. No. 1 to latest. In good order. Genuine

buyer. Particulars to A. Zerbst, Chinchilla, Q. Mf ANTED—Good Magnetic or Crystal Pickup,

also Dual Wave Coll Unit. Price and particulars to L. A. Jantke. Gnlgn. S.A. AT/ANTED. R. & H.. Vol. 6. Nos. 1. 2. 3. 5. 7. '' 10. Price and partlcularc to D. R.

McGulre. 2(1 Godfrey-street, Toowoomba, O.ld, (Tl/ANTED TO BOY. Magnetic Pickup.

complete. Ken McLennan, Woodcnbong, via Kyogle. (Vl/ANTED to buy Radio & Hobble?. Vol. 1. *' Nos. 1 to 8. Good condition. A. G.

Squires. 35 Bowmer-slreet, Banksia, N.S.W. AT/ANTED: Collaro or similar Pick-up or '' Head only, must be swivel, detachable

type, pay good price. J. E. Raven, -182 Chapel-road, Bankstown, N.S.W. UX0809.

- H

Triplets. £1/10/- each. As new.

QELL. Qty, 1W Curb, Resistors, 3 Gng. Var. ^ & Mfr. type flat ppr. Condensers, etc. Write for price list. Smith, 53 Bellevuc-ave., W. Hyde, N.S.W. CELL; Q.S.T. 1937 and 1933 22/6 Weston

0-190 m.a., £2/10/-. Wanted: Q.S.T. Yearly Binders, D104 Crystal Microphone or Shurc Double-button Carbon Microphone. J. F. Anderson, Nullawarre, Vic. T7*OR SALE: 9 Valve Communications Re- ' celver. 9.5 to 550 Metres. Slorrar, l£0 Penshurst-st., Penshurst, Sydney. Tel. 1.112191. ITSOR SALE; K475 1-0-1 M.A. Meter, 600-0-600

• scale. Best olfer, C. J. Reid, 24 Eramclt- strect. Smithton. Tun. TOOB SALE; RCS. DW35, Coil Dnll. RP. Det,

Oso. B/C and S/W. £2. 9 Flat. 96 Frenchmans Road, Randwick. Sydney. TTtOR SALE. Complete kit parts build 6- -1 valve battery radio, valves, speaker, chassis. £5. R. Markham, GwabeBar, N.S.W. (lOR SALE. R-C.S. D.W. Coll Kit. with R.P.

M/ANTED Vol. 1, Nos. 1, 2. 3. 4. 5, 6, and Vol. 2. No. 12. of "Radio & Hobbles,"

good price given. L. S. Lynch. 264 Commer- cial-street, Mr. Gambler, sth. Aus, [WANTED In good order 51n.-61n. cleclro- 1 ' ' magnet Speaker, 7000 ohm. field matched to single pentode: 2-ganK "H" Condenser. J. Stack, 24 The Boulcvarde. Cammcray, Sydney. WANTED: "R. & H." Apr.. 1943. Can ex- ' ' change Aug. or Sept., 1942. J. Edmonds,

31 Anlhony-st., Ormond, Vic. Y\7ANTED: 32L7GT Valve, new or good used. '' Chief Telegtapbist Lewis, F.N.D., West-

ernport, Vic. WANTED: Vols. 1 and 2 "R. & H.." also ' June. July, 1941, and Jan., 1945. Also

Pick-up, Cheap. For Sale or will Exchange for above articles; One "B" & "C" Eliminator plus 2.6V. to 6.0V. Heaters. £5/5/- or oiler. Also 2 Chassis, old Speakers. &c. Send for List. J, Howard, 60 Cheltenbam-rd., Beceroft, N.S.W. 4^1 OLP BALLS wanted, new or good condi-

tlon. Used Balls. Buy any quantity. Walker. 4AT, Atherlon. Q'uecnslaml. / 'ONDS., Valves, Transformers, Eliminators. ^ Pick-up. Oflers. T. Cooke. Brlgg-road,

F-PP'"g. tCOMPREHENSIVE Home Study Short Story

^ Writing Course, modern, £3/10/-. G. Lloyd, "Shangri-la," Alan-street, Cammcray. SELL—2 meters 0-10 m.a. Radio Corp. and

Trlpl . Ryan, Coolup, W.A. J^tNE Wlndcharger, 'complete. Assembly,

Generator, Propeller 6fi., Axles, Bearings. Gears. £5/10/-, XWg497. IJELL Pickups (2) Xtal. laboratory type In-

struments, offset heads, black finished base and head. Chrome arm, perfect balance. Never used, £12/10/- each. W. Scolt. 316 Riversdale-road, Hawthorn Vic.

Stage and two I.P.s to match. £3/18/-. V. J. Valden. Cedar-Party, via Wlngham. rjtOB SALE: New and Used Parts, Gangs.

Colls, Speakers. Trannies, &c.. and Valves, including two SOV's. Wanted. Lathe, A.C. Motor. Vs-Va h.p. B. W. Pearson. Walgctt. lÔR SALE; Trickle Charger £2, 'A amp. 4- £3/10/-. also larger "B" Eliminator, new rectifier, £4. 4-gang Condenser. £1/5/-. Also 2. 3 gang. G. Hlllicr, Box 13, Edgeclllf, N.S.W.

R SALE: 150 M.A. Trans. Prl. UOV. Sec. 1^6 600-0-600V. PH.. 2.5V., 7V. and 14V. Plus 240V.-110V. Trans, to suit above. Also two S.H. 50's. Excel, cond. Apply U. L. Semmler, 195 Greeiihlll-rd., Toorak Gdns., S.A. 1[COR SALE: Brlggs and Stratton Home Light-

ing Engine and Dynamo, 6-voll. as new. £25. Two Old Receivers, with Valves, Speak- ers; 5V. Neutrodync. 6V. Ddlsco, £3 ea. II. Turner, 141 Carlingford-rd., Carllngford, N.S.W. TJVDR SALE: Complete Vibrator Power Umt L (new Vibrator), plus Filament Choke and Condenser, together with new 6D6 and 76 Valve, also Morse Key and Buzzer. The Vibrator Unit Is from a set converted to A.C. operation. The lot for £5, add freight. J. Watt, 15 narllcur-st.. Deniliquin, N.S.W. IÔR SALE: DC multimeter, perfect order,

£6 , Console Wireless. 45 Balmoral- St.. Waltara, NSW. r|SAKE any oiler One Complete 12ln. Mag- -L navox Speaker. 405 rectifier type with handle, suit amplifier; two Morse Keys, two Buzzers: one pair Phones; one Double Pilot Choke (30 Henry 30 Henry); one 8-inch Gul- bransen Speaker. 7500 field, no trail. Single Gang .0005 Var Condensers: also reaction. A. E. Winter, Booker Bay. N.S.W. I(VOIt SALE:—New and used Valves, Plug-In J- Cell Formers, Reaction, single and 2-gang Condensers, Resistors, fixed Condensers. 75- watl Soldering Iron, Permag Spkr., Spring Gramo. Motor. Flex, coll-wlndlng wire. Audio- trans, 28 copies "Radio & Hobbles" from October. *42. 12 copies "Radio World" from Jan., *44, plus a lot ol haudv "Junk." Write for list to G. Dcwey, P.O., Moss Vale. N.S.W.

A. E. Eyres (Kingaroy, Q): It seems the receiver is going well now.

B. Uatlis (Coraki. NSW): A fine log as usual. You are experiencing very fine reception. Will write soon.

D. Lanyun (.Mildura, Vic.): Hope that the report to VQ7LO Is on the way; a letter is sent from this one.

J. MelvMIo (Auckland, NZ): Our hopes that the receiver is OK. Plenty of scope for you now.

J. Cochranc (Croydon. NSW): Thanks for the curd, will return same very soon.

G. Glllelt (Dudley Park. SA): Very grale- ful for your help. Good log from you also. I have noted the mention on the veries.

A. Cushen (Invercargiu, NZ): Your letters much appreciated, Nice log again this month. Will no doubt receive th» book this week.

J. Dixon (Parramatta. NSW): Sorry that things look so black Just now. Will get you more schedules as soon as possible. Regards.

R. Collins (Gunning. NSW): Will look forward to a bigger log next month. Yon may be able to look us up while down here.

K. Burke IKillara, NSW): Interested in the dope on the Australians. The schedules of many stations are changed now.

J. Paris (Prospect. SA); Good work this month. Will be glad to hear from you. as possibly you have a few suggestions.

F. Hampshire (MoKlnnon. Vic.):: Thanks lor the address, hope you are pleased with the veries.

K. Oulten. Ilaberfleld (NSW): The 4ZR card Is something new, a letter has been Issued In the past. Notes about APRS Noumea appear on our DX page.

A. Zerbst. Chinchilla (Qld.): Pleased to hear about your veries. Glad you like our magazine.

H. Shcra, Rockhamplon (Qld.): Shall write you concerning our hobby.

A. Platt. Ashficld (NSW): Pleased to hear about the set you built, shall write you shortly.

W. Wall, Snowtown (SA): Shall forward by mail addresses required.

I.AC G. Peterson (Nth. Qld.): Believe 4PM Is now oil the air.

I. Tonkin. Ferntrce Gully (Vie.): Pleased your 3UL card arrived.

L. Gllddon, Cpwey (Vic.): Thanks a lot for VHO notes, glad you liked the book.

A. Towns, King Island (Tas.): The KXEL folder Is certainly attractive. Your reception notes make Interesting reading.

C. Reid, Smithton (Tas.): The proposed Darwin -station was reported last month, with call-sign SDR.

A. McDonald. Euroa (Vic.): Pleased you've visited Melbourne again. Hope you soon get the rain you need your way.

A. Peterson, Charleston (SA); OCI's channel will be 1430kc.

M. Phillips. RAAF: Many thanks for WSYJ and WVTL notes.

S. Smcllle, Croydon (NSW): Pleased to hear about your veries, and very glad you like our magazine. /

B. Baker, Hermidale (NSW): Interested AO know 2CH is not verifying yet.

K, Jones, Forbes (NSW): I note that the landllne dispute has thus far prevented your 2PK Joining the Macquarle news network.

J. West. Kogarah (NSW): Pleased to know you are rapidly becoming Interested In DX. Lot's hear from you some more.

E. Moore, New Farm (Qld); Your latest veries are Jolly fine.

O. Kelly. Bowcn Illlls (Qld.): Pleased you. loo. have the new 4ZR card. The new WOAI folder Is very nice.

BELIEVE IT OR NOT We can supply practically any type of radio valves for almost any type of set, including English, European, American, and Australian types. Don't delay, write now. as our stocks cannot last for ever. DENHAM'S (M'bro.) Pty. Lrd.

Maryborough, Queensland.

Printed and Published by Associated Newspapers Ltd. (successors to Sun News- Spers Ltd.) at the registered office of tho

mpany. 60-70 Elizabeth-street. Sydney.

PAGE FORTY-FOUR RADIO AND HOBBIES FOR JUNE, 1945

JUNE, 1945 RADIO AND HOBBIES IN AUSTRALIA PAGE III.

MORSE COl>E KEY SETS AND niZZER.

/V ■si (iin.

.Morse Sel. Hiebesl Grade Adjust- able Morse Key. P.M.G. Type I with Ilieh Tone Buz/er. Mounted with Battery. 27/B.

Tho Handy- man's Mir- ror. HI/!), or 11 - posted handle, Iin.

mirror. All nlck- ellcd silver. For all Tradesmen. Radio Builders. Watehmakers. etc. See Into the cor- ners and hidden places. It's all metal and hean- (ifnlly made.

|V OF&a\*r,

Adjustable Morse Set. Buzzer Battery. Fittings. Mounted read> for use. on wooden baseboard. P.M.G. De Luxe Adjustable Mors< Set on wooden base, with Buzzer Light Switch, and Battery. .W- Morse Set. Adjustable He Luxe Key, Buzzer, Switch from lieht to buzzer. Battery, mounted on baseboard. 25/-.

The Second . (Overseas) '

Edition of the British

Radio Amateur's Handbook. 10/0.

or II/- posted and packed. Containing

3*28 pages of the most valuable data on Modern Radio Science.

f Radio \ WaNDBook.

"Vtfcla, Radio

P.M.G-V£ IMG rrp' •OONDFR

35/- 19/6 \djustablc ■ Ml/

Morso Keys. 2/0, plus — postage. Adjustable Buzzers.

i

m

Electric Soldering Irons. Highest

possible grade. One Year Guar- antee. Flex, 1/3 yard extra. Add iiilTicient postage. 1011-watt Light Duty. 33/-; 100 watt Heavy Duty, 16/6; ISO-watt Heavy Duly. 53/0.

Folding Leather

Pocket and Note Wallet

Combined. Gold

Stamped A.I.F., R.A.N., or R.A.A.F. Symbols 5/6, or 0/- posted. Now Ready 05 Postcard Size Photos

of planes and all particulars 15/- Set. plus postage. All the World's Most Renowned Planes in Fullest Detail. Aeroplanes in Detail from Original Drawings. A wonderful publi- cation, 5/3. The best of Its kind.

BO I I N CIGAR- «OLIX ETTE ROLLER. '/!' posted

Aircraft Idcntiftca- tion, prepared by

the Publish ers of ■•Aeroplane." 3/9 each, oi t for M/-. plus postage Full of pic-

tures and fullest latest details Part I. British Monoplanes; 2 German Monoplanes; I. Amerlcar Monoplanes with the R.A.F.: 3 Japanese Aeroplanes.

Two Famous Books by Gbirardi.

Each 42/fl. plus 1/3 postage.

Radio Physics Course. En- larged Second

Revised Edi- tion. A Com- plete, Up-to- date, Authori- [lative Course.

Explains ___ Sound Elcc- />H " tricity. Radio.

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Modern Radio Servicing.

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Volume. Self-Study Training Course In Practical Repair for all kinds of Radio. Explains thoroughly Radio Equipment Installation. Adjustments and . Maintenance, also how to operate a Radio Repair Service. 700 Illustrations. Nearly 1400 pages. 12/0. plus postage.

BROWN'S BOOK OF SIGNAL- LING. Learn International (odes and Sig- nals. Ail Mefh- ods Explained. Colored Plates. Learn Morse by Light and Sound Semaphore with Procedure.

Ship's Signals, Flag Signals, etc.. etc. II/- posted.

Jeweller's Magnifying Eye Glass for Stamp Collectors, Mechanics,

etc. Nirkelled metal finish. II/- posted.

Levcnson's F u n Book. For Home, Camp, Parties, etc. Endless fun. Thou-' sands of Laughs/ Jokes and Puzzles/ Ventriloquism, Card Tricks, F ii n n y

Stories. Mono- amcs. Conjuring Tricks. Fun for Boys and Girls. Recitations. Card Games. Forfeits, and other Features. New Party Gamps. New Ideas. New Jokes. Price 2/9, 3/- posted.

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Grade MAG ING GLASS. Nick-

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CAR AERIALS. Chromed Mela L Three Section Tele- scopic Car Aerials, extendable 2« to «K Inch. 35/-. plus postage.

The Book of Practical Tele- vision. By Dow- ding. Over 3011 Pages. Fully Illustrated. A Thorough Out- line of a Most Interesting Sub- jet. «/«, or »/- posted.

POCKET KNIVES with Real Steel Blades. Hard, Long - wearing Serviceable Com- bination Pocket or Bell Knives, for all purposes. For the Man in the Street, the Bushman, Sea-

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10/- posted. 1-Bladcd with Top Lifter. I/I I. or 5/3 posted. All for hard wear.

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Makes 'cm like the factory. Full Directions.

Kcliable Cigarette Lighters, small pocket tubular type, as Illustrated. 3/9 re- tail. Packed and posted, 4/3. Also Storm proof, 12/- posted.

IN" LUMINO

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3/9 posted.

Plans To Build 0 Miniature Models of Famous R.A.F. Planet (Non-Flying). The Spitfire. Hur- ricane, Falrev Battle. Wellington. Harrow Bomber, Blenheim Bomber. Six Plans for 2/0. oi 2/9 posted. British Products Just Arrived: Clear Celluloid Circular Protractor. 5in., 7/II; Serol-clrcle, flln., 4/-. Dour las Combined Protractor and Parallel Rule, 6/U.

NEW BOOK. Just from London.

Simple Metal Works. 19/- posted. One of Famous "How To Do It" Series.

The Blade- v\>- Saver Razor \Jlj Blade Sharp- ener. with Strep at base. Easy to use. 3/-. or 3/0 posted. Just arrived. New Book from Lon- don. Add postage. British Air- craft. by Savillc Sneath. In two parts. 9/9 each part, plus postage Long Playing G\*m

K0'

phone Needles. 4/11; 5/3 packed and posted. 1(H). each plays 10 minutes.

Build Your Own Models from Simple Easy To Build Plans. 00 Gauge Models Make Realistii Miniatures. The full Sel of Plan: 2/9, or 3/- posted. Terminal Station. Line Side Hut, Loading Gauge. Weighbridge. Loco Shed Buffer Stops. Cattle Pen. Signal Goods Shed. Footbridge. Signal Cabin.

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Stormproof Sure-To- Llght Cigarette Lighters, 11/6, or 12/- packed and posted.

©:

Mode] Plane Kits. Solid Models, 3/3. or 4/- packed and posted... .. _ . ... tt-,. Catallna. Spitfire, Lockheed. Lan-!L<a",fr robacco Pouches 13/0. caster. Tiger Moth. Short Stirling, Packed and posted. Dragon Six, Mosquito. Always make second choice. ft/11, or (1/8 packed and posted: Blackburn Roc.. Harvard Trainer 30 Therraalidcr, Russian Red Stai

Men's Plaited Kangaroo Waist Dress Belts. 8/0. or 9/- posted. Tan finish.

Kangaroo Leather Plaited Belts Fighter. Westland Lysander for Men and Women. 8/11, or 9/0 Alwavs make second choice. packed and posted.

J. LEVENSON'S RADIO Games, Hobbies. Novelties and Slot Machine Specialists.

220 PITT STREET, SYDNEY. Everything from A to 7. In Radio at Sane Profit Prices. Phones M2525 and M2526-7 Goods forward C.O.D. Post or Rail over 10/-. (C.O.D. Rail within N.S.W. only; not Interstate.)

PAGE IV. RADIO AND HOBBIES IN AUSTRALIA JUNE, 1945

Tteimo brixrih '***"'

r.

/

x

NOTHING

SUCCEEDS

LIKE

PROFICIENCY

HERE'S PROOF "I'm blessing fhe day I started with A.R.C.

Already I've earned enough to cover all expenditures, including (I) Course paid for. (2) two Meters value pre-war £26. (3) four Radios to learn on and experiment on, plus a fair amount of stock, value, roughly. £ 15—and best of all. worth more than all—A DECENT

H.B., Western Australia.

TRAIN AT HOME, IN CAMP, OR AT OUR

BENCHES A.R.C. offers ambitious men a sound, proven course in Radio Engineering. Sound because •t is the result of many years' successful operation, proven because hundreds of ex- students owe their present success to the college You can learn with equal facility at home, or even in camp with your unit (by means of our Correspondence Course), whilst the modernly- equipped College workshops are available to night students

THE end of fhe war must find you prepared and proficient if your Future is to be assured. An unskilled

man will be at a great disadvantage in the Post-war World with its keen competition and commercial readjustments. Radio is a young industry which has shown remarkable progress in the last few years and its future possibilities are unlimited. Radio engineering wants trained men urgently, ambitious men make big money. You can assure your Future by embarking on a sound course of technical training now. Don't delay, the sooner you start to train the sooner you can take your place in one of the most vital and fast moving professions.

0

Measurements of one millionth of ...

inch by Radio is now possible. Think of it, these incredibly small dimensions may be accurately read with electric gauges. These gauges respond to changes in reactance caused by the thickness of the material under test. Such electric gauges are being used to measure the thickness of films or coating on magnetic surfaces, metal platings, and the thickness of insulating material and iron and steel. Here is a remarkable new application of the 20th Century's "wonder worker"—RADIO!

ARCI042.

YOU CAN START RIGHT AWAY

Right now openings in Radio are greater than the number of men available to fill them. Here are three good reasons, more- over. why A.R.C. Radio Training must interest you so vitally: (I) You will enter to-day's most progressive industry: (2) You will be pulling your weight in the war effort; (3) You will have a splendid career ahead of you when the war Is over.

IT COSTS LITTLE Think of this—for a few ponce per day—

actually less than many fellows spend on tobacco—you can prepare yourself for a man-sized job in Radio NOW.

AUSTRALIAN

RADIO

COLLEGE

PTY. LTD. Cnr. Broadway & City Road, Sydney. Phone M6391, M6392

PREVIOUS KNOWLEDGE UNNECESSARY

You don't need 3 knowledge of Radio or Electricity—we'll give you all you need of both, in a simple, practical manner that makes learning easy, presented, too, in such a way ♦ hat you remember what you're taught and speedily gain the opportunity to PRACTICALLY use your knowledge A.R.C. Training fully covers Radio Service Men's Licencing Requirements.

SEND FOR THIS BOOK First thing to do if you want to secure vital Radio facts is to send for "Careers in Radio and

Television," a lavishly illustrated book published by the College and available to approved enquirers. Send Coupon for your FREE COPY NOW!

I To Mr. L. B. Graham. Principal. | I Australian Radio College Piy Ltd.. | I Broadwap. Sydney. 'Phone 3f6391-2. I J Dear Sfr.—/ am interested m Radio. J

Please send me. without obligation on - . my part, the /ree book. "Careers in J J Radio and Television."

.\'AM£ ADDRESS

Documents

t f-W*- -nr. r'r PLANS-TEMPEST & FIREFLY · >OV-en s\ sc^ \PC- C' e ->1 in IllS ... Thomas—Electricitywe owe to our children ... The problem of stowage was one