Paae Four

r;~pOF TOWERL 750 FEET

/WE TAKE radio for grant-

ed. We sit in our livingrooms and turn on a

switch. We dial a station. Ifwe like the program of the mo-ment we listen. If we are dis-pleased we turn it off. But wedon't ask many questions aboutits magic.

If some one asks, ••How doesradio really work?" one can,of course, dismiss him lightly byexplaining: ••As I understandit, sound goes into the micro-phone, it's sent through the air,and then it comes out of theloud-speaker."

But it isn't as simple as that.No. But some day your curios-ity may be piqued. It will be ifyou chance to drive by W-G-N'slofty new radiator some twentymiles. northwestward from Chi-cago.

Let us say you are bowlingalong Rohlwing road (route 53)on a Sunday afternoon. Sud-denly you behold a tower sweep-ing skyward. Up. Up. Up.Higher than Tribune Tower. Asyou draw nearer you realize thatit is probably the highest thingyou have ever seen. Soaring up750 feet, this new transmittingtower is the tallest man-madestructure in all Chicagoland.

Silhouetted against blue skyand fleecy clouds, it hangs therelike a giant needle, suspended,perhaps, from the heavens byan invisible thread. On closerview you find that it actuallyappears to rest on the earthand that it is kept in position bytwo sets of guy cables that an-chor it to the ground. A beau-tiful, graceful tower of steel.

As you drive on you may ask,••Why build such a tower?"The answer is progress. Andprogress in this instance meansgreater public service. W·G-Nis committed, as are all broad·casting stations, to operate ••inthe public interest, convenience,and necessity." W-G·N meetsthis responsibility fully.

Since 1935W-G-N has spent amillion dollars to offer listenersthe best station in America.Three-quarters of a million dol-lars went into its new studioquarters. During the last yearW-G-N spent an additional quar-ter million dollars to increasethe efficiency of its transmissionsand to make its reception thebest.

Already much evidence hasbeen accumulated proving thatW-G·N's objectives are beingrealized even more fully thanhad been expected and that theyare meeting a wider public ac-ceptance t han eve r before.Today no station has a finersignal or greater coverage.

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(Tribune photo.)

The radiator, or tran.mitting tower. Irom which emanate wave. carryingW-G·N programs. Whit. building is tuning house.

If you happen to be a Chlca-goan you may say that W·G·N'sreception has been irreproach-able. All you needed to do wasto turn to 720kilocycles and yougot what you wanted. Trueenough.

But there were localities awayfrom Chicago where receptionconditions were not all that wasdesired. Listeners at a distancewho sought programs bearingthe characteristic s tam p ofW-G·N were sometimes disap-pointed.

Radio interference just whenthe bases are filled is an aggra-vation. These problems of un-favorable reception long chal-lenged the ingenuity of the tech-nical men of radio. Now theyhave found a partial solution inthe vertical radiator.

The vertical radiator, or trans-mitting tower, has been foundto be much superior to the oldtwin towers with antenna strungbetween them. Under the oldsystem the wires drawn betweenthe towers were responsible forthe radiation, or dissemination,of the radio waves. The towersthemselves in most cases servedprimarily to support the anten-na and only secondarily had anyeffect on the transmission ofprogram matter. Often specialprovisions were made to mini-mize the effect of the towers onthe transmission.

The old antenna system usedby W-G-N at its Elgin plant wasof the ••T" type, that is, it con-sisted of a vertical wire support-ed by a horizontal conductingmember at the top. Its endswere insulated from and sup-ported by two towers spaced 500feet apart. Each tower was 250feet high.

A few years ago it was dis-covered that an ideal antenna

CLieaao Sunday Tribune

would take the form of a giantpole hanging from the sky.Such a position, it was found,would provide for the more ef-fective dissemination of radiowaves. But a giant ••curtainrod" can't oe hung from acloud. And even-if it could, howcould one attach the wire carry-ing the potential speech andmusic from the studios to it forsending into the sky? So engi-neers did the next best thing.

They fashioned a tall towerand balanced it on end. Thiswhole tower is electrified fromthis pin point to its tip. Radiowaves fly out at every point andangle along its whole height.The tower itself has taken theplace of the old style antenna.

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The new W· G . N radiator,which r i s e s 750 feet aboveground, is of the vertical type.Its uniform cross section simu-lates the effect of a single wireor a cage of wires.

A radio tower is a little likean iceberg. What you see abovethe surface is only a small por-tion of the whole. It tells onlya fraction of a fascinating story.

In building W-G-N's new trans-

By LARRY WOLTERS

cons are employed to serve aswarnings to aircraft.

W-G·N's tower is surmountedby two 5()().wattflashers produc-ing alternate luminous periodsof one second and darkness ofone-half second. Lights of avia-tion red (a sort of orange red)are inclosed in prismatic globes.From the 650-level downwardthere are lights at 1oo-foot inter-vals. Since the lights have a li!eof about 2,000 hours, frequentclimbs all the way to the topare required by a service manto make replacements.

An electric eye (photo-electriccell) pointing into the north skyatop the transmitter house athousand feet away automatical-ly assumes the chore of turningon the tower lights when thelevel of daylight falls below acertain minimum.

The tower is painted with al-ternate bands of red and whiteto serve as warning in the day-time. Nothing in the public In-terest and safety has been ror-gotten.

Weighing 65 tons <l30,000pounds), the tower is supportedby a single pivotal base of porce-lain less than a foot in diameter.From this ••pin point" base the

With the new type of antennaas a radiating element it is pos-sible to produce a discriminationin favor of waves transmittedhorizontally along the groundas compared to tho s e sentangling skyward. This is im-portant. This discrimination en-abIes the station to increase andexpand its ••primary servicearea." (There is also a ••second-ary service area," which will betouched upon later.)

With the new antenna a con-centration of radio energy inthe space just above the earth'ssurface occurs, and a correspond-ing reduction of energy sent sky-ward results. This coneentra-tion is desired because it is thispart of the radio wave which isused to serve territory within300 to 400 miles of the station bydaytime.

Beyond this distance the radiowave just above the ground(called ground wave by the radioengineering fraternity) becomestoo weak and is no longer useful.

Anything that can be done toincrease the strength. of this sig-nal will increase corresponding-ly the primary service area.

That the new radiating systemhas reached out farther is evl-dent from reports of improved

ful value. {Radio waves bounceback from the atmosphere muchlike a handball thrown againsta wall. If thrown directly at thewall the ball returns almost tothe spot from whence it wasthrown. If thrown at angles itwill return at varying distances.The greater the angle the great-er the distance.>

When a high-angle signal isreflected back to earth at a pointwhere the ground wave still hasstrength we have in effect atthis point two signals. The re-flected sky wave at this pointwill interfere with the groundwave. This causes the undesir-able phenomenon k now n toevery listener as fading.

The fading effect may be corn-pared to the reverberations orechoes noted in a large, bareauditorium. Reflections of aspeaker's voice may make hiswords unintelligible in certainparts of the hall,

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This radio interference will bemost destructive at points wherethe two signals (ground andsky) are of nearly equal value.The affected area exists at theouter boundary of the primaryservice area.

Clearly, then, at night an un-desirable condition exists. Thismust be minimized or rectifiedif possible. That is exactly whatthe new W-G-N radiating systemattempts to do-to push the fad-

Diagram showing how radio waves are reflected by the Heaviside layer.

mitter plant many interests hadto be considered, many obstaclessurmounted, numerous problemssolved. Several factors were in-volved in selecting the site. Itis important, for instance, thatthe subsoil be suited for radiotransmission. An ideal locationwould be a tidal flat where saltwater could lap the base of thetower. It is imperative to avoidgravelly or sandy soil. Depositsof ore must be avoided. In thisregion tests show a good clay(truck garden) subsoil, whichcleaves tightly, is the best. Thesite chosen answers to this speci-fication.

Public sa f e t y, convenience,and pleasure had to be remem-bered. Old receivers and faultyinstallations in homes' some-times result in interference fromn ear b y transmitters. ThusW·G·N sought a sparsely populateed area. It found the most thin-ly populated area in the countynortheast of Roselle. Fewerthan 4,000 persons live withina radius of five miles.

Measures to protect the publicsafety: The radiator is built ona tract of land of 101 acres andat a point a quarter mile fromthe highway. Even if it wereto fall-and that is not anticipat-ed, since it is designed to with-stand gales upward of 110 milesan hour-it could topple in anydirection without striking thetransmitter house or any otherstructure. The entire tract isadequately fenced to restricttrespassers who might be imper-iled by high voltages.

The tower is almost five milesoff regular air routes. It can-not be a hazard to air travelers.No radiators may be built ex-ceeding 490 feet in height on ornear regular flying lanes.

Radio towers on air routesmust be topped by rotating bea-cons. When located off the reg-ular flying courses flasher bea-

shaft spreads out into an equi-lateral triangle ten feet on aside, and in this shape risesstraight upward 750 feet.

The guy cables, also insulatedfrom the tower, are so tightenedthat they exert a tremendousdown pull on the insulator,which can support. 900 tons.

A factor exerting a profoundinfluence on the strength of theradiated signal is the groundsystem installed beneath thetower. From a copper mesh 48feet square lying directly underthe tower 120 lengths of copperstrips stretch outward radially800 feet from the tower like thespokes of a wheel. These strips,one-half inch wide and 1/32 inchthick, are buried eight inchesin the ground. More than 18miles of these strips are used inthis underground system.

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These ground wires and towertogether form what is called theradiation system. Its counter-part in the home on a smallerscale is the antenna, or aerial,and the ground to which the re-ceiver is connected.

A W·G·N engineer gave thisexplanation of why a groundsystem is needed in conjunctionwith the antenna for good sig-nals:

••To establish an electricalcurrent in the tower a ground isneeded.

••The cur r e n t establishedin the tower is responsible forthe signal. But the ground sys-tem is required for establishingthe current. The ground sys-tern does no radiating; the towerdoes that."

The new type of radiating sys-tem is used because its formand dimensions have been foundto produce g rea t I y superiortransmissions to those previous-ly employed.

reception from every direction,particularly fro m Michigan,Iowa, Wisconsin, and, of course,Illinois.

Strengthening of the groundwave has improved reception topoints 400 miles or more away.The signal strength has beenraised about 40 per cent and theprimary service area substantial-ly increased.

The night time transmissionsalso are improved by the newradiating system. To under-stand how, it is necessary to be-come acquainted with a phenom-enon known to scientists as theKennelly-Heaviside layer. This••layer" consists actually ofmany strata of gases one abovethe other up in the" ionosphere"which surrounds the earth likethe stratosphere does. The Ken-nelly-Heavlslde layer, named forits co-discoverers, v a r i e s inheight from 60 to 200 miles.

Radio signals sent upwardfrom the antenna at night arereflected back to earth at vary-ing angles from these layers. Aportion of the wave reflectedback to earth is directly respon-sible for long-distance reception.This distant area lying beyondthe primary service area iscalled the secondary servicearea.

In this area radio service isreceived almost entirely fromthe wave reflected from theupper atmosphere-from the skywave--because the ground waveat this distance has been ab-sorbed.

The distant reception is pro-vided by that portion of thewave reflected b a c k at lowangles (see diagram for clarity).So this portion of the wave isdesirable. But signals are radioated also from the antenna sky-ward at high, or steep, angles.These cause trouble. They comebouncing back to earth wherethe ground wave still has a use-

Ing area outward from the trans-mitting station.

By reducing the signal sentskyward at high angles and in-creasing the signal sent out dt-rectly above the earth at low

.angles the fading area is reducedand the area served by theground wave augmented.

The new radiating system hasdemonstrated that it has accorn-plished these results-expandingthe primary service area, whilemaintaining coast-to-coast recep-tion (secondary service area)with a minimum of fading area.

In the above discussion termssuch as ••along the ground,"••into the sky," ••ground wave,"and" sky wave" have been used,However, these are descriptiveonly. It should be rememberedthat radio waves, in commonwit hot her electromagneticwaves, including light, requireno material medium for trans-mitting or carrying them.

They appear to travel throughempty space. The inability tounderstand the propagation ofthese waves without requiring amaterial medium led scientiststo postulate an ••ether" or ••all-pervading medium." But theexistence of such an ••ether" hasnever been affirmed.

Much more than a new radiat-ing tower is required to providesuperior W-G-N service. Behindthe tower is the new transmitterhouse, where the radio pro-grams, or their electrical equlv-alents, are made ready for send-ing out. Beyond the transmit-ter house are power lines forbringing the tremendous volt-ages required in a modern radiop I ant, the special telephonewires that carry the programsfro m the studio at TribuneSquare. And behind the micro-phone are the performers them.selves.

To appreciate the rOle of the(Continued on page live.)

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Putting "Voice of the People"

Rear new of the traumitter house. where .,oltage ia recei.,ed fromcommercial power .ubstationa.

(Continued from perge four.)magical new transmitter plantlet us start at the beginning:

A pianist, let us say, strikes anote-middle C-in W-G-N's bigaudience studio. Before the per-son in the last row has heard itradio will have carried the tonearound the world. FOr radiotravels with the speed of light-more than 186,000.miles a sec-ond. Sound waves travel justa little over 1,000 feet a second.

For radio, then, it is necessaryto combine sound waves' withradio waves. A sound wave setsair in motion. The pitch deter-mines the number of vibrations.For middle C it is 256 vibrations

a second. For higher notes thenumber of vibrations would becorrespondingly greater.

These vibrations in the airare converted into electrical im-p u I s e s by the microphone.When middle C is struck themicrophone will vibrate 256times a second. Behind its sur-face flows electric current. Asthe microphone responds to themiddle C Vibrations, so does theelectric current.

The microphone con v e r t ssound waves into electrical fre-quencies in exact accordancewith those set up by the soundwaves.

These vibrations of electricalenergy in this form will notcarry through space. So theyare conducted by telephonewires to the radio transmitter.

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Here these electrical equiva-lents for sound are built up totremendous intensities; the yare ••modulated," or superim-posed on radio waves. Finallythey are radiated from thetransmitter system into space.In the receiving sets of the na-tion they are reconverted intosound.

All this takes place practicallyinstantaneously. But it is avas t I y complicated matter.There is the matter of obtaininga supply of electrical power andpreparing it for broadcasting.

Two power lines carry to theW·G·N plant the electricity nec-essary to operate the many unitsthat are needed. One line car-ries 33,000volts from Waukeganto W-G·N's If north" substation.The other carries 12,600 fromMaywood to a If south" substa-tion. The first is the regularsource of power, the second an

••Hot .tic:k" iD use to c:lo.. .witch in the powerdiatribution room. It .afeguards the operator.

HeatiDg unit for traumitter house and part of cooliJlg .y.tem fortube. u.ed in tran.miuion.

The Story of a Mighty.Transmitting Station

alternate or emergency source.These substations are just offthe road on the W-G-N site.

The substations contain trans-formers for reducing the volt-ages to 2,300volts. In this statethe power is carried by under-ground cable to the basement ofthe transmitter house, Here itis metered and distributed.

That portion of the powerwhich is to be used in the trans-mitter proper must undergo con-

Front Yiew of the traumitter hOWie,in which are located iDJItrumenta

pictured on thia page.

siderable refinement before itis usable. Up to this point it is••raw" alternating current. Be-fore it can be used it must bechanged into If pure" or If untpo-tential" current. This refine-ment is made in a unit called arectifier.

Then the rectified current ispassed through a filter. Herefinal traces of "ripple" are' reo.moved. If this were not donethe radio or carrier wave wouldproduce an annoying hum inhome receivers.

The current is now ready foruse in modulation. Modulation,you remember, is the coupling ofthe signals, or sounds from thestudio, with the radio wave orcarrier. A carrier wave is just

about what it says. Like ahorse, it carries a "rider," therider in this case being the mid-dle C note that has been sent outto the transmitter from thestudio. This" load" is broughtfrom the studio through specialtelephone wires. .

The signals from the studioencounter the modulator, whichunites them wIt h the radiowaves, created by a crystal oscil-lator. The loaded carrier must

operate in a given pathway.That is the station's frequency.W-G·N is assigned to 720 kilo-cycles. Each station must stayexactly on its pathway of rre-que n c y. In the transmitterhouse are instruments to checkon its adherence to the channelon which it is licensed to Opeerate.

A cannon cannot be fired with-out ammunition. That is true ofradio waves, too. Before theyare ready for projection theymust be tremendously strength-ened, or amplified. This takesplace in the tubes of -the trans-mitter. There are six stages' ofamplification. Four types oftubes are used. These vary insize. The largest cost $1,650each.

A whole set of tubes costsaround $7,000. A' complete set

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of spares must be kept on handat all times.

High power in radio transmit-ters is possible only because ofwater cooling in the tubes. Thetubes are not very efficient.They waste power in the formof heat, Alr-cooled tubes ofmore than 5,000 watts are im-practical. But water -cooledtubes of 100,000-watt capacityare practical and in regular use.W·G-N uses two such tubes.

An elaborate water -coolingsystem is employed to keep thetubes cooled to a safe operatingtemperature. One hundred gal-lons of distilled water is pumpedthrough the jackets of the tubesystem each minute. Some ofthe heated water is divertedthrough a ventilating systemand provides regular heat forthe building in the winter time.

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In describing a process that isexceptionally elaborate it is easyto err on the side of slmplfflca-tion. A transmitting station isa vastly complicated combina-tion of electrical and mechani-cal units. These play manyrOles, some obscure to laymen,but all necessary.

The transmitter house is filledwith automatic devices designedto keep a broadcast on the airin the event of many types offailure - electrical, mechanical,or human elements. In the eventof the failure of a normal sourceof power supply a selectorswitch will employ an auxiliaryor emergency line.

Complicated organisms re-quire a nerve center to operate'and control them. As may beexpected. a modern transmitterhas such a coordinating center.It is called the master. controldesk. In it are located a scoreor more controls. Many indiocators are watched by an oper-ator who sits in a comfortablechair.

Some of the things indicatedor controled on its panel are:

Power line voltage and cur-rent. .

P I ate voltages on varioustransmitter units.

Current in the antenna.Audio program level going

into the transmitter.Percentage of modulation.Deviation from the assigned

frequency.Lights indicate the proper op-

eration of numerous units in thecomplete transmitter. There aremany other controls and indiocators-batDing and mystifying

View toward radiator from 'traDa-mitter hou.e.

p••• Five

on the AirW-G-N-Modern Radio MarvelA Tour Through the Plant That Makes

Possible Your Favorite Program

Basement tank .toriDg diatilled water. and pumps that circulate it throughtube cooliJlg .y.tem.

W. R. Crane of W-G-N .taff at the master control boaret. where are located automatic device. to maintain contin-uity 01 broadca.t. Thia i. the ne"e center of the traumitter unit.

to anyone but a technical ex-pert. To him they are filled withmeaning. They give him controlover mighty forces with his fin-ger tips. This type of controlmakes for greater efficiency inoperation, as well as for safety.

A radio station is never un-attended. Even when it goes offthe air it requires the presenceof technicians to care for it.

After the radio cargo has beengiven its last boost in amplifica-tion it leaves the transmitterhouse, whence it is sent by atransmission line to a little cubi-cle at the base of the insulatorcalled the tuning house. Hereit is given one final touch beforeit is ready to go out on the air.

And then comes the final dra-matic step of transmitting, orthe flashing of the s i g n a I sthrough space.

To capture this electric cargoyou must know the roadway it istraveling. In this intance setyour dial at 720 and the receiverwill do the rest. In a fiash mid-dIe C will be sounding in yourears. While it took many min-utes to read this article, it reoquired only the tiniest part of asecond for this note to reach you.Such is the magic of radio.

One of the giant tube. u.ed intransmitter and mentioned in con-

nection with picture at right.

Telephone amplifiers through which pay electrical impul.es carrying pro-gram from W-G-N .tudio •• Checking panel is used to keep tab on equip-

ment.

Tranaulltter front panel. Behind doors are giant tube. u.ed to amplifypower. (Tribuae photo ••)