E L E C T R I C A L A N D M E C H A N I C A L

E N G I N E E R I N G R E G U L AT I O N S

T E L E C O M M U N I C A T I O N S

R E C E P T I O N S E T A R - 8 8

D E S C R I P T I O N

(Provisional)

This information is provisional and is supplied for guidancepending the issue of more complete instructions. All errorsof aTechnical nature should be reported in accordance withE . M . E . R . T e l s . A Y - 0 0 9 *

' i

I s 0 u e 1 , D i s t r i b u t i o n C o d e N o , 4 May 1945

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ELECTRICAL AKD MECKLNICALE N G I N E E R I N G R E G U L AT I O N S

TELECOMMUNICATIONSG¥-6aa-

R E C E P T I O N S E T A R - 8 8

D E S C R I P T I O N(Provisional)

This Informtion is provisional and is supplied for iuidancepending the issue of more complete inst ruct ions,o f aTechnica l nature should be repor ted in accordance wi thE . M . E . R . T e l s . A Y - 0 0 9 ^

A 1 1 e r r o r s

G E N E R A L I N F O R M A T I O N

G E N E R A L D E S C R I P T I O N

1 . The Reception Set AR-88 covers short wave, standard broadcast, and C.W.services, its principal use being for high frequency communications. It is designedto withstand severe climatic and line voltage variations without appreciable impairmentof performance. Its features include five degrees of selectivity, three of which in¬clude acrystal filter. The frequency coverage is arange of 535 to 32,000 Kc/s in sixb a n d s .

E L E C T R I C A L D E S C R I P T I O N

The circuit consists of two stages of R.F. amplification, first detector, localoscillator; three stages of I.F. amplification, second detector,, noise limiter, B.F.O.;one A.F. amplifier stage, and an output power stage and power supply system.

The frequency range of the set is 535 to 32,000 Kc/s covered by six bands as

2 .

3 .f o l l o w s :

B a n d 1B a n d 2

B a n d 3B a n d 4B a n d 5B a n d 6

535 to 1,600 Kc/s1,570 to 4,550 Kc/s4,450 to 12,150 Kc/s

11,900'to 16,600 Kc/s16,100 to 22,700 Kc/s22,000 to 32,000 Kc/s

I

The aerial coupling system is designed to provide optimum coupling from a200 ohm transmission line, (except in the broadcast band). The first tuned circuit isprovided with atrimmer condenser adjustable from the front panel, which ensuresthe proper tuning of this circuit with any aerial system. For the standard broadcastband, conventional aerial and earth connections should be used.

The aerial terminal board is provided with three terminals, two of which maybe joined together with alink. When asingle wire is used, the link should be closed

4 .

}

5.

Issue le Vey, 1945 D i s t r i b u t i o n C o d e N o . 4 Page 1

ELECTRICAL AND MECHANICALE N G I N E E R I N G R E G U L AT I O N S

TELECOfiMUNICATIONSG¥-622

and the aerial connected to ‘‘A”. If an earth is used, it should be connected to “G’’.If atransmission line or balanced input is used, the link should be opened and the lineconnected to terminal “A” and the centre terminal.NOTE: The receiver is manufactured with apermanent bus wire connection to the rearof the aerial terminal board, between the centre and earth terminals. If balanced in¬put operation with open link is required, this connection on the rear of the aerialt e r m i n a l b o a r d m u s t b e r e m o v e d .

The outputs available from the set are three:

2.25 ohms impedance for loudspeaker output from the terminals at the rearmarked ^^2.25 ohms’’,

(b) 600 ohms impedance for input to line from the terminals at the rear marked600 ohms”,

(c) Headphone output at the panel jack marked ‘‘PHONES” for phones of im¬pedance up to 20,000 ohms. With phones plugged in to the first positionthe loudspeaker output remains on, but plugging the phones right homecuts out the loudspeaker. NOTE: Hneither the 2.25 nor the 600 ohm out¬put is in use and it is desired to use phones they must be plugged fuUyhome to load the output valve correctly.

6 .

(a)

U

7 The power pack is movinted on the receiver chassis and consists of apowertransformer, rectifier valve RCA-5Y3GT, and filter. Atap switch is provided at the

for changing the power transformer voltage tap. The voltage for which the switchis set may be read directly on the switch. The receiver may also be operated from6V L.T. and 250 to 300V H.T. batteries, or from aVibrator Supply Unit such as theR.C.A. MI-8319 (See Tels. IY-212/2).

r e a r

MECHANICAL DESCRIPTION

8. The receiver and its main power supply are built on one chassis with the frontpanel which slides into ablack crackle finished cabinet and is bolted in position withtwo metal strips which run down either side of the panel. The cabinet is provided withahinged lid to enable the valves to be reached easily. The R.F, Unit is avery rigidsub-assembly, bolted to the chassis proper, which may be replaced comparitivelyeasily as aunit. \

9. The slowr motion drive to the main condenser shaft is specially designed forlow backlash and smooth operation, incorporating anumber of spring loaded doublegear wheels and aflywheel. The main dial is calibrated in frequency for each of thesix bands and at the bottom has 16 main divisions each of which is subdivided by thevernier dial to the right of the main dial into 100 smaUer divisions. Thus it is possibleto log accurately the turning point of any particular station.Page 2 Issue 1, May, 1945

ELECTRICAL ARD MECHANICALE N G I N E E R I N G R E G U L AT I O N S

T3LECOMMUNICATIOHS-SY-6a2

10. Weight and Dimensions.

Weigh t :Height :W i d t h :Depth:

9 7 l b s .1 1 i n c h e s19-1/4 inches19-1/4 inches

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I.-'

G Y - 6 2 21 - 1

F I G . 1 . F R O N T PA N E L V I E W

P A N E L C O N T R O I S

T U N I N G C o n t r o l

11 . The single tuning control in the centre of the panel operates the main tuninggang condenser and the two dials. The left hand dial is calibrated in Mc/s except inthe case of the lowest frequency band which is calibrated in Kc/s. The main dial hasascale for logging, which the vernier dial simply subdivides.

i

1

O F F - T R A N S M I T - R E C E I V E M O D U L AT I O N - R E C E I V E C . W . S w i t c h

1 2 . This is aTour-position switch. Starting from fully counterclockwise thesep o s i t i o n s a r e :

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TELECOl f t ^UKICATIOBS ELECTRICAL AND HECHANICAL 'E N G I N E E R I N G R E G U L AT I O N S

Transmit. Position which gives energized valve filaments, H.T. off, andshor ted terminals for a t ransmit ter re lay on the speaker terminal boardon the back of the chassis. Connect arelay to these.two terminals for trans¬mi t ter operat ion.

2 .

R e c e i v e M o d u l a t i o n . N o r m a l r e c e p t i o n .3 .

Receive C.W. Beat frequency oscil lator switched on.4 .

R A N G E S w i t c h

Situated to the right of the Off-Trans.-Rec. Mod.-Rec. C.W. Switch is theRANGE switch marked in six positions. These are the band numbers as stated in para¬graph 3and the desired band is selected by turning the switch.

13 .

R . F. G A I N C o n t r o l

This continuously variable sensitivity control is for use in conjimctionwith theaudio gain control for all manual gain operation. With A.V.C. on, it should, as arule,be set to eliminate interference, otherwise R.F. GAIN should be at maximum.

1 4 .

A U D I O G A I N C o n t r o l

15. See paragraph 14.

S E L E C T I V I T Y S w i t c h

16. This is afive-position switch with the following functions:

1. I.F. bandwidth for high fidelity modulated reception.(19.2 Kc/s wide at 20 db down).

2. I.F. bandwidth for normal modulated reception.(12.8 Kc/s wide at 20 db down).Crystal Filter in -for C.W. telegraphy or sharp modulated signal reception.(8.8 Kc/s wide at 20 db down). .

4. Crystal Filter in -for sharper C.W. telegraphy.(7.6 Kc/s wide at 20 db down).

5. Crystal Filter in -for sharpest CWtelegraphy.(5.6 Kc/s wide at 20 db down).

NOISE L IMITER -A .V.C. Swi tch

3 .

This is afour-position switch and starting from the fully cotmterclockwise' 1 7 .position the settings are:

-No. A.V.C. and no noise el imination1 . M A N .2. MAN.N.L. -No. A.V.C. but with noise elimination

Issue 1, May, 1945Page 4f

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E L E C T R I C A L A N D I f fi C H A K I C A LE N G I N E E R I N G R E G U L AT I O N S

TELECOIJMIINIC ATI ONS

£

3 . A V C . N . L .4 . A V C

- A . V . C . w i t h n o i s e e l i m i n a t i o n-A.V.C. only, without noise elimination

B . F . O . C o n t r o l

18. This control is used for C.W. code signals, or for the detection of weak R.T.signals. It gives the reqvdred audio pitch after tuning the receiver, and usually shouldbe set slightly off central position for the desired beat frequency.

N O I S E L I M I T E R C o n t r o l

1 9 . This control sets the receiver for operation at the required percentage valueof Noise Limitation. The fully clockwise position limits the noise interference to de¬sired signals with 100% modulation only. As the knob is turned counterclockwise,the noise interference is limited to continuously lower percentages of modulation, sothat in the fully counterclockwise position the Noise Limiter is operative on any mod¬ulation whatsoever, but this position gives bad intelligibility to well modulated sta¬tions. Normally the fully clockwise position will be used, but imder extreme conditionsof interference abalance point should be fotmd for maximum intelligibility of signalw i t h l e a s t d i s t o r t i o n a n d l e a s t n o i s e .

T O N E C o n t r o l

This is avariable control for reducing H.F. response. In the fully clockwiseposition the full tone is obtained and as the control is tm-ned counterclockwise, hightones are lessened. It should be set to suit the particular tonal conditions for thesignal being received.

Aerial Tuning (‘‘ANT”)

2 0 .

2 1 . The tuned circuit to which the aerial is coupled is provided with this trimmercondenser to enable any aerial to feed the R.F. stage as efficiently as possible at allfrequencies. It should be adjusted for maximum signal strength.

T E C H N I C A L I N F O R M A T I O N

To follow the detailed operation of the circuit, afew words of explanation arenecessary of the conventions used for the bank of switches S1-S24 which appear onthe circuit diagram. Figure 1001.

(a) Switches are shown as they would appear to an observer looking from thefront of the receiver, i.e. aclockwise rotation of aknob turns the centrering of the switch in aclockwise direction on the circuit,

(b) Atag shown thus^l indicates that it is used solely as asoldering tag andh a s n o e l e c t r i c a l c o n n e c t i o n w h a t s o e v e r w i t h t h e s w i t c h .

2 2 .

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ELECTRICAL ARD MBCHAKICALE N G I N E E R I H G R E G U L AT I O N S

t e l b c o u e u n i c a t i o n sG I - 6 2 2

(c) Atag shown thus with no wire apparently leading from it indicates thatthe tag is electrically connected to its corresponding number on the reverseside, e.g. tags 1on S13 and S14 are joined together,

(d) All switches are shown in their furthest counterclockwise position.

As inferred in (c) above, each switch section has afront and back switch to it,i.e. one piece of insulation is used for the two switches, and they are numbered with thelowest number to the front of the receiver, running in pairs SI and S2, S3 and S4 andso on. S23 and S24 are exceptions to this in that S23 is asingle layer wafer and S24is an ordinary mains on-off switch.

2 3 .

R.F. Stages

Table 1lists the tag numbers of each switch which are connected together ateach of the RANGE settings. This table will assist in following the operation of thecircui ts expla ined later.

2 4 .

R A N G E 5 R A N G E 6R A N G E 4R A N G E 3R A N G E 2R A N G E 1S W

1,3,11,121,3,11,122,77,8,101,3,5,6,117,8,101,3,5,6,9,111,5,112,3,67,8,101,3,5,6,9,111,5,112,3,67,8,101,3,5,6,9,11

1,3,11,121,11,123,11,121,3,12S I2 . 92,52,31,22,11S 28,9,103,5,6,7,11

4,5,81,3,6,114,5,81,3,6,7,9,111,7,112,3,44,5,81,3,6,7,9,111,7,112,3,44,5,81,3,6,7,9,11

2,3,41,6,112,3,41,5,6,7,9,111,5,7,11

1,2,4,122,10,11,125,6,72,10,11,121,3,5,6,7,91,3,5,7

S 3

6,7,111,2,4,123,5,6,7,9,113,5,7,11

S 48,9,101,3,5,6,7,11

S 5S 6

1,5,7,113,8,98,9,101,3,5,6,7,111,5,7,11

S 7S 8 2,31,99,11

2,3,41,5,6,7,9,111,5,7,11

1,2,4,123,5,6,7,9,113,5,7,11

2,10,11,121,3,5,6,7,91,3,5,7

S 9S I OS l l

8,92,31,9S 1 2 9,118,9,101,3,5,6,7,11

2,3,41,5,6,7,9,11

1,2,4,122,10,11,121,3,5,6,7,9

S 1 33,5,6,7,9,11S 1 4

9,117,115,113,111,11S 1 58,11 10,116,114,112,1111,12S 1 6

TABLE 1. TAGS WHICH ARE CONNECTED TOGETHER AT EACH POSITION OFT H E R A N G E S W I T C H

The R.F. amplifier is designed to provide ample selectivity ahead of the firstdetector for minimizing cross modulation and blocking effects from strong inter¬fering signals and for obtaining ahigh degree of image signal suppression. The amp¬lification is adjusted to provide optimum signal-to-noise ratio by making the gain ofthe first valve as high as practicable. The set is provided with the two R.F. stagesusing 6SG7 valves as conventional amplifiers deriving grid bias from the A.V.C, line.

!The aerial is coupled to the first R.F. stage by transformer coupling and the twostages are similarly inter-coupled.

2 5 .

1

l e s a a M a y , 1 9 4 5Page 6

T E L E C O M U N I C AT I O N S

The H.T. to the two stages is taken from the Main H.T. Line and is decoupledby R3 and Cll for the anode and further by R1 and Cl for the screen grid of VI. Thedecoupling for V2is RIO and C63 for the anode and further by R6 and C33 for the screen.Band switching is accomplished by means of aganged bank of switches numbered Sl -S16 of which Sll -S16 are used in the first R.F. stage, and S7 -SIO in the second.These switches are in pairs, afront and arear portion -the front one having thelower Snumber and switching in the coils required, while the rear portion generallyarranges that certain coils which would normally be ‘‘floating” are, in fact, earthed.

On the input side to VI, S16 connects the aerial to the appropriate input coilLI, L3, L5, L7, L9 or Lll, while SI5 puts an earth on the lower end of the coil sele¬cted by S16. It should be noted that if abalanced input is used, i.e. the bus wire andlink from TBl are removed and the balanced input connected to the top two terminals,that these two switches apply this input across the appropriate input coil, except in thecase of the L.F. band, RANGE 1, where the lower end of the coil LI is permanentlyearthed. Also, in the case of the RANGE 1, awave trap comprising the series reso¬nant circuit L57 and C12 is included in the input circuit to provide alow impedancepath for the intermediate frequency of 455 Kc/s. S13 connects the appropriate second¬ary of the input transformer L2, L4, L6, L8, L10.or L12 across its main timing conden¬ser, C3 or C6 or the two in parallel as the case maybe, and couples this tuned circuitvia C4to the grid of VI. C3 andCG are two condensers on the main tuning gang assem¬bly and are chosen to give agood L/C ratio on each band. The two L.F. RANGES 1and 2are tuned by C3 and C6 in parallel, RANGE 3byC3 alone, and the H.F. RANGES4, 5and 6by C6 alone. The “live” ends of these coils are earthed when not in useby the switch S14. RANGES 3, 4, 5and 6are provided with extra capacity by C7, C9,CIO and C120 respectively. The output from VI is coupled to the input of V2 by eithertransformer coupling or capacity coupling. On RANGE ithe anode circuit of VI com¬prises L13 and C36 in parallel, resonant off the L.F. end of the range to give amorelinear gain characteristic. (Generally, an untuned coil at the L.F. end of any band hasamuch lower impedance than at the H.F. end and so the gain of the stage is reduced).On RANGE 2the anode circuit comprises LI5, shunted by R8 to give amore constantgain over the band, coupling into L16. On RANGES 3, 4, 5and 6the anode load is L17coupling into L18. On RANGE 3transformer action couples the two R.F. stages. OnRANGES 4and 5the coupling is by the capacity of C8 and C5in series, while on RANGE6the coupling is through condenser C5 only, C34 being the grid condenser. It will benoted that there is aseries resistor R7 on RANGE 1between the input coil and switchS9, which is included to keep the gain of the stage down to the required figure by de¬creasing any regenerative effect which tends to occur at the low frequencies concerned.Sll is the earthing switch, and on every RANGE earths the “Live” end of the two ofthe three coils L13, L15 and L17 which are not in use.

ELECTRICAL AKD MECHANICALE N G I N E E R I N G R E G U L AT I O N S

26.

2 7 .

Switches S7-S10are similar in their operation to switches Sll -S14. S9 con¬nects the appropriate coupling of the grid coil, L14, L16, L18, L19, L20 or L21 acrossits main timing condenser,. C35 or C40, or the two in parallel as the case may be, andcouples this tuned circuit via C34 to the grid of V2. The two L.F. RANGES 1and 2are tuned by the two condensers C35 and C40 in parallel, RANGE 3by C35 alone, andthe H.F. RANGES 4, 5and 6by C40 alone. The “live” ends of these coils are earthedwhen not in use by the switch SIO. The output from V2 is coupled to the signal input

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ELECTRICAL AND MECHANICALE N G I N E E R I N G R E G U L AT I O N S

grid of V4 by either transformer coupling, or by capacity coupling. On RANGE 1theanode circuit of V2 comprises L23 and C58 in parallel, resonant off the L.F. end asexplained above, coupling into L24. On RANGE 2the anode circuit comprises L24,shunted by R18 to give amore constant gain over the band, coupling into L26, and onRANGES 3, 4, 5and 6, the anode load is L27, coupling into L28. On RANGE 3trans¬former action coupled the 2nd R.F. stage to the mixer. On RANGE 4the coupling isby C61 while on RANGES 5and 6the coupling is directly on to the grid condenser C57.S7 is the earthing switch, and in every Case eafths the '‘live’' end of the two of thethree coils L23, L25 and L27 which are not in use, through C63. The trimmers on the2nd R.F. grid circuits are C37, C38, C39, C41, C43 and C45 on RANGES 1to 6res¬pectively, and, in addition RANGES 4, 5and 6have extra capacity C42, C44 and C46 ;respectively.

L o c a l O s c i l l a t o r

The local oscillator is aligned to track with the R.F. amplifier at 455 Kc/shigher than the signal frequency, thus producing a455 Kc/s intermediate frequency inthe mixer anode circuit which is amplified further in the I.F. stages. The oscil latorvoltage is regulated by the RCA VR-150 regulator valve to provide maximum frequencystability imder conditions of variations in power supply voltage.

The circuit employs a6J5 valve in amodified Colpitts circxiit which has beensimplified in the cases of RANGES 1and 6in Figures 2and 3respectively. The cir¬cuit for RANGES 2and 3is similar to that for RANGE 1except for component valueand nomenclature, and in the same way the circuit for RANGES 4and 5is similar tothat of RANGE 6. S3 connects the anode of V3 viaC14 to the "anode end” of the appr¬opriate coil and also connects the desired timing capacities C50 and C49 in parallel

RANGES 1and 2, C50 alone on RANGE 3, and C49 alone on RANGES 4, 5and 6. S4earths the "anode ends” of all coils of the. frequency ranges lower than the one in use

! (with the exception of the RANGE 1coil in the RANGE 6position), as such un-earthedi coils may resonate with their self capacity and create an imdesirable absorption effect.

Incidentally, other coils axe also earthed. S2 connects the grid of V3 via C13 to thegrid end” of the appropriate coil while SI earths those ends of the coils which are

not in use. Referring to Figures 2and 3, C13 and R4 form the grid leak system forthe oscillator while C14is chosen to give the .right degree of feedback. C17,C20, C23,C24, C28 and C30 are the condensers on RANGES 1to 6respectively which are usedfor tracking purposes. C16, C19, C22, C25, C27 and C32 are trimmers for RANGES1to 6respectively, while C15, C18, C21, C26, C29 and C31 give additional capacity.The local oscillator output is coupled to the mixer, V4,-via C53 on to its control grid.

2 9 .

3 0 .

o n

i t

M i x e ri

The two inputs to the mixer, V4, the signal and the local oscillator have al¬ready been discussed. The valve is cathode biassed by R13 and C52 and the controlgrid is "tied” to earth by R14. The screen supply is obtained from the screen supply

!of V5, decoupled by R19 and C54. The six different grid coils for RANGES 1-6 areI L24, L26, L28, L29, L30 and L31 respectively which are selected by S5 in asimilar

manner to the selection of coils in the R.F. circuits. At the same time S5 connects

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Issue lo May, 1945

t e l e c o m m u n i c a t i o n s€ ¥ - 4 2 £ELECTRICAL AND MECHANICAL

ENGINEERIHG REGULATIONS

R l lC I 4

\ [ W W W W H T +

V 3K >

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_ / C 4 6==g. z ; c i 67C49 7

ooooo R 4o

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1 - 2

fig. 2. SIMPLIFIED OSCILLATOR CIRCUIT -RANGE 1

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VWWW\A H.T +w) o V 3oo C49 ^o C32 = C 3 I

7 - Too

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FIG. 3. SIMPLIFIED OSCILLATOR CIRCUIT -RANGE 6Page 9Issate 1* May, 1945

T E L E C O M r a i C AT l O N SCI«6.22..

ELECTRICAL AND MECHANICALE N G I N E E R I N G R E G U L AT I O N S

tuning condensers C77 and C70in parallelfor RANGES 1and 2, C77 only for RANGE 3and C70onlyfor RANGES 4, 5and 6. It will be noted that the series resistor R17is in¬cluded on RANGE 1between the input coil and switch S5 in order to reduce the gainto the desired value by decreasing any regeneration which tends to occur at these lowfrequencies. S6 is the switch which earths the '^live^’ ends of the coils not inThe anode load of V4 is the tuned primary of the I.F. transformer L32 -L33 reson¬ated by C55, damped by R15 to give aflatter response, and the H.T. supply for theanode is obtained from the Main H.T. Line, decoupled by R16 and C56.

u s e .

S E L E C T I V I T Y S w i t c h

3 2 . The table below indicates the connections made at the various positions of theSELECTIVITY switch and should be used for reference during the description of theI.F. stages.

P o s i t i o n 1 P o s i t i o n 3 P o s i t i o n 4 P o s i t i o n 5P o s i t i o n 2

2, 3,41, 11, 122, 121 , 4

2, 3,41, 11, 12

2, 3,41, 11, 12

2, 3,41, 11, 122, 11

2, 9, 106, 7, 11

S 1 7S 1 8S 1 9

1, 31 , 21 , 8S 2 0 1 , 8

TA B L E 2 . TA G S W H I C H A R E C O N N E C T E D T O G E T H E R AT E A C HP O S I T I O N O F T H E S E L E C T I V I T Y S W I T C H

First I.F. Stage

The first I.F. stage consists of the 6SG7 valve V5, cathode biassed byR20, \m-bypassed as there is ample gain without coimteracting Hie degeneration. The outputfrom the first I.F. transformer L32 -L33 is tuned byC72 and with the SELECTIVITYswitch in positions 1or 2the ^^top” end of L33 is connected directly to the grid of thefirst I.F. stage while the centre is at R.F. earth potential due to C76. However, inany one of the three narrow positions of the SELECTIVITY control 3,4 or 5the ^Hopend of L33 is connected to V5 grid through crystal Al,455 Kc/s, while the bottom endof the coil is connected to V5 grid through variable C75 to the grid of V5 to give ananti-phase component balancing out the effective shimt capacity of the crystal and itsholder. This is the conventional crystal bridge circuit, but the Qof the coils is notexcessively great. The bandwidth at 6db down is adjusted to 400 c/s, 1,500 c/s or3,000 c/s on settings 5, 4and 3respectively. The anode circuit of V5 comprises theload introduced by transformer L35 -L36 whose primary is resonated by C78. H.T.,is supplied from the Main H.T. Line decoupled by R22 and C79 for the anode potentialand from the Secondary H.T. Line bypassed by C71 for the screen potential.

3 3 .

Second I.F. Stage.

V5 is coupled to the second I.F. valve, V6, through adouble transformer com¬prising L35 -L36 and L37 -L38. In addition, L35 -L36 has afurther winding L39,

Issue 1, May, 1945

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TELECOVMUNICATIONSGaf-£22_

ELECTRICAL AND MECHANICALE N G I N E E R I N G R E G U L AT I O N S

and L37-L38 has L40. In positions 2, 3, 4, and 5of the SELECTIVITY switch L39 andthe two windings of each transformer to give abroader (and squarer) pass band. L36and L37 are tuned byC89 andC90 respectively, and the jimction of these two condensersis held at R.F. earth potential by C92. The output of this transformer is developedacross L38 timed by C91, and is connected directly to the grid of V6. The anode loadof V6 is that introduced by L41 tuned byC94 and the anode receives its H.T. from theMain H.T. Line decoupled by R26 and C95, the screen voltage being obtained from thesame point as the screen voltage for V5. The cathode has abias resistor R25 which,similarly to V5, is un-bypassed.

Third I.F. Stage

The third I.F. stage is always operated at full gain, being connected neither tothe A.V.C. line nor to the R.F. GAIN control. The object of this is to ensure that thereis always asufficiently large A.V.C. voltage applied to the grids of the controlledvalves to avoid there being over-loaded by the incoming signal. This also permits theC.W. oscillator to be coupled to the grid circuit of this stage, giving acomparativelyhigh detector excitation voltage with small electrical coupling to the oscillator circuit.The method of coupling the output from V6 to the grid circuit of V7 is similar to thatfor inter coupling V5 and V6. In the case under consideration the double transformerconsists of L41 -L42 and L45, and L43 -L44 and L46. The intermediary timing con¬densers are ClOO and ClOl, the common point of which is held at R.F. earth potentialby C102. Valve V7 is cathode biassed by R32 and C106 and the D.C.path from grid toearth is completed by R33, the output from L44 being applied between earth and gridof V7 via C105. The anode load of V7 is that introduced by L47 tuned by C108 and theanode receives its D.C. potential from the Main H.T. Line through L47 via decouplingR 3 4 a n d C 1 0 7 .

3 5 .

S e c o n d D e t e c t o r

The output from the 3rd I.F. stage is coupled into the second detector, one ofthe diodes of V8 through the transformer L47 -L48. 1^8 is tuned byC114 and is con¬nected in the normal manner in ser ies with the diode and i ts anode load R48 and R49.This load, which is by-passed for R.F. by Cl 15, also provides voltages for the NoiseL i m i t e r c i r c u i t a n d A . V. C . w h i c h a r e d i s c u s s e d l a t e r .

36 .

A u t o m a t i c V o l u m e C o n t r o l

The A.V.C. vo l tage is obta ined f rom the second detector va lve. Avar iabledelay is obtained depending on the setting of the R.F. GAIN control. The second heter¬odyne (C.W.) oscillator excitation voltage is just lower than the delay diode bias vol¬tage so that it does not decrease the sensitivity of the receiver. The 2nd diode in V8is used as adelay diode with R47 comprising its main anode load. Asimplified dia¬gram of this portion of the circuit is shown at Figure 4, and to which reference is nowmade. The incoming signal, rectified, provides aD.C. voltage across R48 and R49making the point Anegative with respect to B(earth) by an amount depending on thestrength of the received signal. The cathode of the delay diode is similarly negative toearthby virtue of the voltage drop across the ‘earthed’ end of the R.F. GAIN control R46.

Page 11

3 7 .

!

I

Issue 1. May, 1945

ELECTRICAL AND MECHANICALE N G I N E E R I N G R E G U L AT I O N S

TELECOMMUNICATIONS

T O S E C O N D D E T E C T O RD I O D E O F V 8

A . V . C . D I O D E L O A D D

WW\AAA T O A V . C . L I N EA I y

T O N E G A T I V E O F

P O W E R P A C K

D E L A Y D I O D ES E C O N D

D E T E C T O R

D I O D E

L O A D

R 4 8&

R 4 9

+

G A I NR 4 6 & R S 5

+

B

T W

F I G . 4 . S I M P L I F I E D A . V. C . C m C U I T

Roughly speaking the diode will only conduct when the voltage developed by the signalacross R48and R49 is less than that applied to the cathode, and consequently for smallsignal inputs the diode conducts and the anode potential at D, from which the A.V.C.voltage is taken, almost drops to cathode potential, i.e. to apotential determined bythe setting of the R.F. GAIN control. When the input signal develops across R48 andR49 avoltage greater than that applied between cathode and earth the delay diode isrendered non-conducting and the potential at Dis the same as that at A, so that thevoltage fed to the condenser C48 is the full rectified voltage of the input signal..

The valves receiving bias from the A.V.C. line are the two R.F. stages and thefirst two I.F. stages. The voltage is taken from C48 and fed to V6 via filter R27 andC93 and to V5 by R23 and C76. The voltage to VI and V2 is filtered by R9 and C47and fed to VI via R2, and to V2 by R5. The A.V.C. On/Off switch is combined with thenoise limiter On/Off switch and in the positions marked AVC.NL. or AVC. the AVCcircuit is as described but in positions marked MAN. or MAN.N.L. the main A.V.C.action is eliminated by means of S22 which bridges the anode and cathode of the delay

Idiode. It will be noted that acertain percentage of the A.V.C. voltage (not delayed) isfed to the controlled grids in series with the voltage developed across the slider ofthe R.F. GAIN control by virtue of the voltage drop across R42. This is to help avoid

blasting” by sudden strong signals when using the receiver in the manual gain posi¬tion, the usual procedure when receiving C.W. The A.V.C. action is suitable for useon C.W. because it is arranged that the D.C. voltage at the 2nd detector, produced bythe introduction of the B.F.O. voltage, is less than the delay voltage, and thus switch-

jing on the B.F.O. causes no drop in the sensitivity of the receiver.1

I P a g e 1 2

3 8 .

1

t

Issue !● May, 1945

TELECOMirUNICAT IONS0 5 - 4 2 2

ELECTRICAL AM) MECHANICALE N G I N E E R I N G R E G U L AT I O N S

^ 7 ^N o i s e L i m i t e r - A . V . C . S w i t c h

T h e t a b l e b e l o w i n d i c a t e s t h e v a r i o u s c o n n e c t i o n s w h i c h a r e m a d e a t e a c hposition of this switch, S21, and it should be read in conjunction with the text whichf o l l o w S o

3 9 .

M A N M A N . N . L ^ A V C . N . L . A V C

S 2 1 3,9 7,9 7,9 3,92,11 2,11S 2 2

TA B L E 3 . TA G S W H I C H A R E C O N N E C T E D T O G E T H E R AT E A C H P O S I T I O N O FT H E N O I S E L I M I T E R - A . V . C . S W I T C H

N O I S E L I M I T E R

The noise limiter circuit employed is of the ‘^Series Limiter’’ type, the fimda-mental circuit of which is shown in Figure 5. Consider an unmodulated carrier tunedin and being rectified by diode rectifier No. 1. Assume the carrier is of such strengththat point Aon the diode load resistor is -10 Volts D.C. with respect to earth. ThenBon the diode load resistor will be -5V D.C. (if R48 =R49) which is also the potentialof the anode of diode No. 2. The cathode of diode No. 2returns through R50 and R35to Aand, therefore, diode No. 2will be in aconducting condition. Now if the carrier ismodulated 100%, the peak voltage at Band Cwill rise to -10 volts, and DwillremMnat -10 volts because ̂ e audio from the modulated carrier at Ais filtered out by R35,R50 and C109 and Cl 10. Up to this point (100% modulation) diode No. 2remains con¬ducting and the audio modulation passes through it to the audio amplifier. If the carriermodulation is now increased beyond 100% by apulse of noise or other signal, the peakvoltage at Band Cwill rise correspondingly to more than -10 volts, while Dwill re¬main at -10 volts. When this happens and Cis negative with respect to Dfor the dur¬ation of the modulation above 100%, the diode rectifier No. 2is cut off, and no audiosignal above 100% modulation can pass to the audio amplifier. Therefore any noisepulse or signal whose amplitude is greater than the modulated carrier peak will causethe diode to cut off, and the audio signal wHlbe limited to that value representing 100%m o d u l a t i o n o f t h e c a r r i e r .

4 0 .

Figure 6shows the circuit actually used in the receiver. In practice, it is nece¬ssary to make R48 somewhat greater than R49 since R35 and C109 and CllO act as ashunt A.C. load on R48, and if R48 were equal to R49, distortion would be encoxmteredwell below 100% modulation. It will be seenfrom Figure 6thatR48is apotentiometerwith the arm connected through R35 and R50 to the cathode of diode No. 2. This isdone to provide acontrol which will determine the percentage modulation at which thelimiter begins to cut off. It is evident from the previous description of Figure 5thatif the arm of the control is set at the Aend of R48, the limiter begins to work atapproximately 100% modulation. If the arm is set at the Bend of R48, the limiteris effective as soon as any modulation whatever is impressed on the carrier. Between

4 1 .

Page 13Issue le May, 1945

TELBCOMMUNICITIONS ELECTRICAL AND MECHANICALE N G I N E E R I N G R E G U L AT I O N S

< -

CL F A M R

R 4 8 R 4 9B

D

N * 2

C 1 1 5

I I

R 5 0R 3 5

‘“lAAAAAAAH T +

X T O A U D I O A M P .C I O S A N D C l i o- t - G Y - 6 2 21 — 5

FIG. 5. SERIES NOISE LIMITER CIRCUIT

♦

cL F A M P

R 4 9R 4 - 8 B.AvwvVW'

I I < IN 2 2N fi . I

C l 1 5

C I I 6R 5 0 D

uR 3 5

SAAAAAAA A y

E

A . F A M P.G R I D . R S I

C I 0 9 A N D C l i o

H T +

N * 3- t G Y - 6 2 2

I - 6

N O I S E L I M I T E R C I R C U I T.FIG. 6. RECEPTION SETS AR-88 &AR-88-D I

Issue 1, Way, 1945Page 14

ELECTRICAL AKD MECHANICALE N G I N E E R I N G E E G D L AT I O N S

T E L E C ( » f t ! l I N I C AT I O N SG¥-425.

these two points asetting of R48 can be found which will give maximum intelligibilitywhen listening to asignal xmder extreme interference conditions. This setting willrepresent maximum limiting of the noise and minimum distortion of the signal, andwil l vary with the percentage modulation of the carrier. R48 is the control on theupper right corner of the panel marked NOISE LIMITER.

4 2 . Again referring to Figure 6, it will be noted that an additional diode (No. 3) isconnected across R50. The following explanation will point out the purpose of thisr e c t i fi e r. A s s u m e f o r t h e m o m e n t t h a t d i o d e r e c t i fi e r N o . 3 i s o m i t t e d a n d t h e r e c e i ¬ver is not tuned to acarrier. Then point Ais at approximately the same potential asB, diode rectifier No. 2is in aconducting condition, and noise pulses will come through.In other words the limiter is not effective for weak noise pulses in the absence of acarrier. To make the limiter effective under the above conditions, it is necessary toprovide asmall negative voltage at Cwith respect to Dto cut off rectifier No. 2andcause it to be non-conducting in the absence of carrier. The voltage required is approx¬imately one volt and this voltage is supplied by the contact potential of rectifier No. 3when it is connected across R50. The voltage could just as well be supplied by aone-volt battery cell connected in series with R50, but it is more convenient to use the dioderectifier, and it is just as effective.

The use of diode No. 3has an additional advantage. When asignal is tuned in,point Ais negative with respect to B, diode No. 2is conducting, Cis at approximatelythe same potential as D, Eis negative with respect to Dand No. 3is non-conducting.When anoise pulse representing more than 100% modulation comes through, cuttingoff diode No. 2causing it to be non-conducting, the potential of Dis no longer deter¬mined by Cand diode No. 3immediately becomes conducting through R50, (the contactpotential effect). For the duration of the noise pulse, the low impedance of diode rec¬tifier No. 3in series with C109 and Cl 10 is shunted across the input to the audio ampli¬fier adding i ts effect iveness to the series l imiter. Diode No. 1is the 2nd detectorsection of V8, and diodes No. 2and 3are the two sections of V9.

4 3 .

First A.F. Stage

The output from the Noise Limiter is taken through S21 (See para. 39), to acircuit comprising C116 and R51,the audio gain control. The output from this controlis fed through Clll to the grid of the first A.F. valve, VIO, which is a6SJ7. The gridresistor of this valve is R36 and afixed negative bias is applied to this from the vol¬tage drop across R45 through the smoothing circuit R37 and C99. The valve is cathodebiassed by R39, and negative feedback over both A.F. stages is introduced into thecathode circuit by feeding the output across winding 1-6of T2 through R54, and R39un-bypassed. The valve VIO receives its H.T. decoupled by R41 and C113 through R40,its anode load, from the Main H.T. Line, and the anode load is shunted by the TONEcontrol R52 in conjunction with C117 v;hich curtails the high frequency response. Tli'q^screen voltage is also derived from the Main H.T. Line decoupled by R38 and Cll'2'.’

4 4 .

Output Stage

4 5 . The 6K6GT output valve Vll is fed f^ jin VIO by resistance-capacity couplingIssue 1, May, 1945 Page 15

ELE5CTRICAL AND MECHANICALE N G I N E E R I N G R E G D U T I O N S

TELECO^OTICATI ONS

SJ-6r22 E^SXcomprising R40, C118 and C112, and R53, the latter being taken to asource of negativeDX. potential at the junction of R43 and R44. The anode voltage is derived from thejunction of L49 and L50 and reaches the anode of Vll through the primary of the out¬put transformer T2, while the screen receives its H.T. from the Main H.T. Line.The anode has asmall condenser Cl 19 to remove any high frequencies which havereached that part of the circuit. The output from the set is taken from the secondaryof the output transformer T2 where there are three outputs available, one across term¬inals 1and 2on TB4 which is derived from winding 5-7 of T2 to give amaximum of2Winto 600 ohms, the second across terminals 1and 2of TB2 taken from the winding1-6 on T2 to give 2Winto 2.5 ohms for loudspeaker operation, and the third availableat the phone jack from winding 1-2 of T2 suitable for amaximum of 10 mW into head¬phones of impedance up to 20,000 ohms. When apair of phones is plugged in J2 it firstreaches aposition where both phones and speaker are in operation, and then when theplug is pushed fully home the phones only are operative and winding 1-6 of T2 is loadedby R56 in place of the speaker.

B . F. O .

46. A6J5 valve, VI2, is used in aColpitts circuit as B.F.O. for use when receivingCWThe grid circuit has acondenser C88 and leak R24, while condensers C85, C87aiid variable C86, the panel control, with L22 form the tuned circuit. C82 is chosento give the correct percentage of feedback. H.T. voltage is fed from the H.T. linethrough switch S23 when in the REC. C.W. position, and smoothed and fed through thenetwork C84, R29, C83 and resistance R28, the anode load. This network preventsB.F.O. oscillations reaching the power supply. The output of the B.F.O. is coupled byawire running from an unused pin (No. 4) on the socket of V12 to asimilarly unusedterminal on transformer L43-L44. The very loose coupling thus provided is quitesufficient to produce agood audio signal on C.W. but not too much so that on A.V.C.the sensitivity of the receiver is cut down, thus the A.V.C. operates on both C.W. andR . T .

Power Supply

47 The power required is 100-165, or 190-260 volts 50-60 c/s, and the appropriateinput tapping on transformer Tlhas to be selected by means of S25 situated at the backof the set SwitchS24 is operated when the OFF-TRANS.-REC.MOD.-REC.C.W. switchis moved’from the OFF position, and applies the mains voltage to the transformerprovided that aplug is plugged into socket Jl with links as indicated by the dotted lines.When the receiver is operated from aseparate D.C. supply the D.C. voltages are con¬nected into Jl through pins 4and 5, and 6and 7. T1 has an electrostatically screenedprimary and three secondary windings, comprising a5volt winding for the receiverheater, acentre-tapped 690 volt winding for the rectifier high voltages and a6.4 voltwinding for the valve heaters. The 5Y3GT rectifier, V14, is used in aconventionalfull wave rectifier circuit. There are two stages of filtering with capacity input, thefirst section comprising C96, L50 and C97 and the second section L49 and C98, whileR57 and R58 comprise ableeder resistance. The negative line is taken to earththrough three resistors R43,R44,R45 and the current flowing through these providessuitable negative voltages to earth to bias the first A.F. amplifier from the junctionPage 16 Issue 1. May, 1945

ELECTRICAL. AND 1^ECHANICALE N G I N E E R I N G R E G U L AT I O N S

TELECOMfflJNICATIONS6 ¥ - 4

of R44 and R45, and the output valve from the jimction of R43 and R44. The voltagedrop across these three resistors is fed to the R.F.GAIN control R46, and R55 inseries enabling asuitable negative voltage to earth to be obtained for varying the gainof the R.F. stages and the first two I.F. stages. The H.T. voltage smoothed by onesection of the filter is used only for supplying the anode voltage on the output valve.The fully smoothed H.T. is called the Main H.T. Line and it is fed through R30 to theVR-150 voltage regulator, V13, by-passed by C121, which provides the stabilisedSecondary H.T. Line.

● : »

O F F - T R A N S . - R E G . M O D . - R E G . G . W . S w i t c h

When the OFF-TRANS.-REG.MOD.-REG.G.W. switch is in the TRANS positionit will be seen that contacts 7and 8of S23 are connected together, thus short-circuitingterminals 3and 4on TB2. This short circuit may be used to switch on atransmitter.Also, in this position of the switch it will be seen that the H.T. supply is cut off fromall parts of the set except the output valve anode while all the heaters are kept warmed.On REG.MOD the short circuit referred to previously is removed and all valves aresupplied with the required H.T. except the B.F.O. which is tvithout H.T. until S23 ismoved to REG.G.W. position. Table 4indicates the tags which are short circuited ineach position of the switch.

4 8 .

R E G . M O DO F F T R A N S R E G . G . W .

S 2 3 7,8 4,5 4,5 and 1,2M A I N SS 2 4 M A I N S

O F FM A I N S M A I N S

O N O N O N

TA B L E 4 . TA G S W H I G H A R E G O N N E G T E D T O G E T H E R AT E A G H P O S I T I O N O FT H E O F F - T R A N S . - R E G . M O D . - R E G . G . W . S W I T G H

G R A N G E S O F G I R G U I T F R O M T H A T S H O W N O N F I G U R E 1 0 0 1

The AR-88 at one stage during its manufacture was changed, in name only,tothe AR-88D. This change did not necessarily coincide with any change in circuit andoccurred at some point between serial numbers 3000 and 10,000.

4 9 .

5 0 . The circuit shown in Fig. 1001 is correct for all models, with the followingexcept ions.

(a) Ghanges introduced during production,

(i) The capacities of G15 and G21 have been changed from 15 uuFto. 13 uuF, and G46 from 91 uuF to 86 uuF.

(ii) The ‘‘hot” ends of G37 and G59 have been moved to atap (nowcalled ‘‘tag 4”) on L14 and L24 respectively. The earth end oft h e c o i l i s u n n u m b e r e d .

Issue 1, May, 1945 Page 17

TELECOMMUNICATIONS ELECTRICAL AND MECHANICALENGINEERING REGUIATIONS

T O J I - 7 T B 2 J 24 T 2 I P H O N E J A C KI

o V2 I AB

o I n) oo x 11> oO K 110 3T O S 2 3 - 7 ' *

O X 11c > D04 IT O S 2 3 - 8 - *oOK I> oOK I3

3

0 5T O R 4 7

● &2

T O 6 K 6 G T

A N O D E

2 - 5 i l O U T P U T

I M P E D A N C E F O R

S P E A K E R

R 5 6

V ▼T O R 5 4

FIG. 7. OUTPUT CIRCUIT OF RECEPTION SET WITHS E R I A L N U M B E R S B E L O W 0 0 3 0 0 0

T B 3

! “ 1 2 - 5 / 1 O U T P U T I M P .F O R S P E A K E R

_TJ^2! o i

f

T O J 1 - 7 J 2

4 T 2 I P H O N E J A C KA— o V no

Bo o =2 IO T 0 R 5 4

cTO S23-7-« r

4 ! DT O S 2 3 - 8 oJ O Io 5 Io T O R 4 7 or r - J!

3 21

6 0 0 n O U T P U TI M P E D A N C E ~

T O G K 6 G T

A N O D E

R 5 6(

V

FIG. 8. OUTPUT CIRCUIT OF RECEPTION SET AR-88 WITHCERTAIN SERIAL NUMBERS 003000 &ABOVE I

Issue 1, May, 1945

ELECTRICAL AND MECHANICALE N G I N E E R I N G R E G U L AT I O N S

T E L E C O m m N I C AT l O N SG5-422

(iii) Resistor R59, 15 ohms, 0.5 watt, has been included right upagainst pin 8of VI.

(iv) Resistor R60, 1megohm, 0.5 watt has been shunted across thewhole winding of L34.

(v) Two resistors, R61 and R62, each 10 ohms 0.5 watt, have beenparallelled and connected between pin 2of V9 and the heater line(pin 4on Jl), and the earth on pin 2of V9 has been' removed topin 7.

(b) Differences of circuit in early models,

(i) Two possible variations of the output circuit are shown in Figs.7and 8, the former applying to sets with serial numbers below3000, the latter for serial numbers of 3000 and higher, up to theintroduction of the circuit shown in Fig, 1001. Receivers below3000 (Fig. 7) have outputs for a2.5 ohm loudspeaker and forphones with 2000 ohms impedance or less, later models (Fig. 8)have outputs for a2.5 ohm loudspeaker (on aseparate term¬inal strip), aphone output, and an additional unbalanced‘600 ohmoutput (from the terminals where the 2.5 ohm output was lo¬cated on serial numbers below 3000). The latest circuit shownin Fig. 1001 shows aseparate winding for the 600 ohms im¬pedance to provide abalanced output, a2.5 ohm loudspeakerwinding, and output for phones of up to 20,000 ohms impedance,

(ii) The value of R56 is as shown in Table 1001 except for certainreceivers with ser ial numbers from 3000 up to an unknowns e r i a l n u m b e r w h e n t h e r e s i s t o r w a s 1 0 0 0 o h m s 4 w a t t . A f t e rthat unknown serial number production was resumed with a5ohms, 4watt resistor.

Issue 1, May, 1945 Page 19

T E L E C O M i a J N I C A T I O N SS3L-622

ELECTRICAL Al® liECHANICALE N G I N S E R I K G R E G U L AT I O N S

C O N D E N S E R S

C i r c u i tR e f e r e n c e

C i r c u i tR e f e r e n c e Component Component

}

C l 4,700 uuF3 - 2 5 u u F1 0 - 4 1 0 u u F2 2 0 u u F2 2 0 u u F8 - 6 8 u u F1 8 u u F3 3 u u F2 2 u u F2 2 u u F

4,700 uuF5 6 u u F8 2 u u F2 2 0 u u F1 5 u u F2 - 1 2 u u F5 2 5 u u F1 3 u u F2 - 1 2 u u F

1,550 uuF1 5 u u F2 - 1 2 u u F

3,000 uuF2,700 uuF2 - 2 0 u u F8 2 u u F2 - 2 0 u u F

3,000 uuF8 2 u u F3,900 uuF7 5 u u F2 - 2 0 u u F4,-700 uuF2 2 0 u u F1 0 - 3 7 0 u u F1 8 0 u u F

C 3 7 2 - 1 2 u u F2 - 2 0 u u F2 - 2 0 u u F8 - 1 2 8 u u F2 - 2 0 u u F8 2 u u F2 - 2 0 u u F9 1 u u F2 - 2 0 u u F9 1 u u F

4,700 uuFAssembly, 3sections,0 . 0 5 u F e a c h8 - 1 2 8 u u F1 0 - 3 7 0 u u F4,700 uuF4,700 uuF6 . 8 u u F4,700 uuF6 8 0 u u F

Assembly, 3sections,0 . 0 1 u F e a c h2 2 0 u u F1 8 0 u u F2 - 1 2 u u F2 - 2 0 u u F1 5 u u F2 - 2 0 u u F

4,700 uuF2 - 2 0 u u F

8 2 u u F2 - 2 0 u u F8 2 u u F2 - 2 0 u u F8 2 u u F8-128 uuF

C 3 8C 2C 3 C 3 9C 4 C 4 0C 5 C 4 1

C 4 2C 6C 4 3C 7C 4 4C 8C 4 5C 9C 4 6C I OC 4 7C l lC 4 8C 1 2

C 1 3C 4 9C 1 4C 5 0C 1 5

C 1 6 C 5 1C 5 2C 1 7C 5 3C 1 8C 5 4C 1 9C 5 5C 2 0C 5 6C 2 1

C 2 2C 5 7C 2 3C 5 8C 2 4lC 5 9C 2 6C 6 0C 2 6C 6 1C 2 7C 6 2C 2 8C 6 3C 2 9C 6 4C 3 0C 6 5C 3 1C 6 6C 3 2C 6 7C 3 3C 6 8C 3 4C 6 9C 3 5C 7 0C 3 6

Continued on Page 1002.I

Issue 1, JSay, 1945 Page 1001

ELECTRICAL AND MECHANICALENGINEERIHG REGULATIONS

TELECOfanJNIC AT IONSG J - 4 2 2 -

CONDENSERS (Continued from Page 1001)

C i r c u i tR e f e r e n c e

C i r c u i tR e f e r e n c eComponent Component

C 7 1 Assembly, 3sections,0.1 uF each6 8 0 u u F1 5 0 u u F2 - 1 0 u u F

Assembly, 3sections,0 . 0 1 u F e a c h1 0 - 3 7 0 u u F6 8 0 u u F

Assembly, 3sections,0.1 uF each2 - 2 0 u u F2 - 2 0 u u F5 6 u u F

4,700 uuFAssembly, 3sections,0 . 1 u F e a c h4 7 0 u u F3 - 2 5 u u F

2,200 uuF5 6 u u F6 8 0 u u F6 8 0 u u F6 8 0 u u F

Assembly, 3sections,0 . 1 u F e a c hAssembly, 3sections,0 . 0 1 u F e a c h6 8 0 u u F

Assembly, 3sections,0 . 1 u F e a c hAssembly, 3sections,4 u F e a c h

Assemb ly, 3sec t i ons ,4 u F e a c h

C 9 8 Assembly, 3sections,4 u F e a c h

Assembly, 3sections,0 . 2 5 u F e a c h6 8 0 i m F6 8 0 u u F

Assembly, 3sections,0 . 1 u F e a c h

Assembly, 3sections,0 . 0 5 u F e a c h6 8 0 u u F5 6 0 u u F

Assembly, 3sections.0 . 0 5 u F e a c h

Assembly, 3sections,0 . 0 5 u F e a c h1 8 0 u u F

Assembly, 3sections,0 . 0 5 u F e a c h

Assembly, 3sections,0 . 0 5 u F e a c h2,700 uuFAssembly, 3sections,0 . 2 5 u F e a c h

Assembly, 3sections,0 . 2 5 u F e a c h1 8 0 u u F1 8 0 u u F

2,700 uuF4,700 uuF4,700 uuF3,000 uuF1 5 u u F

4,700 uuF4,700 uuF1 0 u u F

C 7 2 C 9 9C 7 3C 7 5 C l O O

C l O lC 1 0 2

C 7 6

C 7 7C 7 8 C 1 0 3C 7 9

C 1 0 4C 1 0 5C 1 0 6

C 8 0C 8 1C 8 2C 8 3 C 1 0 7C 8 4

C 1 0 8G 1 0 9C 8 5

C 8 6C 8 7 C l i o I

C 8 8C 8 9 c m

C 1 1 2COOC 9 1C 9 2 C 1 1 3

C 9 3 C 1 1 4C 1 1 5C 1 1 6C 1 1 7C 1 1 8C 1 1 9C 1 2 0C 1 2 1C 1 2 2C 1 2 3

C 9 4C 9 5

C 9 6

C 9 7

TA B L E 1 0 0 1 . VA L U E S O F C O N D E N S E R S .

Issue 1, May, 1945 Page 1002n

ELECTRICAL AND MECHANICALE N G I N E E R I N G R E G U L AT I O N S

R E S I S T O R S

■ (

C i r c m tR e f e r e n c e

C i r c u i tR e f e r e n c eC o m p o n e n t Component

R 1 33,000 ohms, 1/2 W2.2 Megohms, 1/2 W1,000 ohms, 1/2 W56,000 ohms, 1/2 W1Megohm, 1/2 W33,000 ohms, 1/2 W10 ohms, 1/2 W5,600 ohms, 1/2 W100,000 ohms, 1/2 W1,000 ohms, 1/2 W10,000 ohms, 1/2 W1,000 ohms, 1/2 W560 ohms, 1/2 W100,000 ohms, 1/2 W15,000 ohms, 1/2 W1,000 ohms, 1/2 W10 ohms, 1/2 W5,600 ohms, 1/2 W33,000 ohms, 1/2 W100 ohms, 1/2 W1,000 ohms, 1/2 W560,000 ohms, 1/2 W120,000 ohms, 1/2 W180 ohms, 1/2 W1,000 ohms, 1/2 W560,000 ohms, 1/2 W120,000 ohms, 1/2 W47,000 ohms, 1/2 W

R 3 0 2,700 ohms, 4W1,000 ohms, 1/2 W390 ohms, 1/2 W2.2 Megohms, 1/2 W1,000 ohms, 1/2 W680,000 ohms, 1/2 W2.2 Megohms, 1/2 W1Megohm, 1/2 W1.5 Megohms, 1/2 W100 ohms, 1/2 W270,000 ohms, 1/2 W100,000 ohms, 1/2 W390,000 ohms, 1/2 W100 ohms, 4W160 ohms, 4W15 ohms, 1/2 W66,000 ohms,2.2 Megohms, 1/2 W66,000 ohms33,000 ohms, 1/2 W560,000 ohms, 1/2 W'2 M e g o h m s1 M e g o h m330,000 ohms, 1/2 W2,700 ohms, 1/2 W6,800 ohms, 1/2 W5 o h m s , 4 W

R 2 . R 3 1R 3 R 3 2R 4 R 3 3R 5 R 3 4R 6 R 3 5R 7 R 3 6R 8 R 3 7R 9 R 3 8R I O R 3 9R l l R 4 0R 1 2 R 4 1R 1 3 R 4 2R 1 4 ● R 4 3R 1 5 R 4 4R 1 6 R 4 5R 1 7 ●

tR 4 6

R 1 8 R 4 7R I 9 R 4 8R 2 0 R 4 9R 2 2 R 5 0R 2 3 R 5 1R 2 4 ' R 5 2R25 * R 5 3R 2 6 R 5 4R 2 7 R 5 5R 2 8 * R 5 6R 2 9

♦Certain receivers as mentioned in Para. 50 (b) (ii).

TA B L E 1 0 0 2 . VA L U E S O F R E S I S T O R S .

Issue 1. Vay, 1945

TELECOMMUNICATIONSELECTRICAL AND MECHANICALENGINEERING REGULATIONS

( j l .C . l . 2031 o f 1BV2J

R E C E I V E R A R - 8 8

FIRST ECHELON WORK

A^ote; This information is provisional and is supplied for iuidance pendini theissue of more complete instructions. All errors of aTechnical nature shouldbe notified throuih the usual channels to Command Headquarters. An OverseasCommand inll forward aconsolidated report with comments direct to theB.A.S. (EME5) Hashington wi th acopy to the War Office (MEIO) . AD.K.Command will forward aconsolidated report with comments to the War Office(MElO) for onward transmission to B.A.S. (EME5) Washington.

.1

( F i g . 1 )M e c h a n i c a l T i m i n g A s s e m b l y.

T o p r e v e n t e x c e s s i v e w e a r o f t h e s m a l l d r i v e p i n i o n m o u n t e d o nthe main tuning shaf t (marked Xin Fig. 1)^ apply asmal l amount ofg r e a s e g e n e r a l p u r p o s e N o . 1 o r N o . 2 t o t h i s g e a r b u t n o t t o a n yo t h e r g e a r s .

1 .

. ? ●

\

I

i

4

x O i Z 3

1 IIII

t S S m U M i III 41 ●■T

i j t i ut H i fi i i i i fi i i u i i M i i r

ii n

j

I

/ M

fX

X Q Y - C 2 3I I - I

FIGURE I. MECHANICAL TUNING ASSEMBLY

■iEND ’A

Page 1,D i s t r i b u t i o n C o d e V o . ^I s s u e 1 . J u l y , 1 9 U U