_,

UHF COMMUNICAT I ON SYSTEM

GENERAL

Two complete and independent systems are installed providing the air crew with UHF radio communications with other aircraft or ground facilities.

These systems, because of their operating frequencies, will be subject to line-of-sight characteristics and the maximum range will depend on the altitude of the aircraft.

AIRCRAFT INSTALLo\TION

The aircraft installation diagram will show locations and general cabling of the systems compocents. Those components are as follows:

• Transceiver RT-641/ ARC-90

• C ontro 1 Panel

S.A-521/A

.AT- 256.A/ ARC

• A•~teuna Selection Panel

SYSTE:\1 OPERA TIO:-<

Since each system is independent of !he other, operation of only one system will be discussed.

VOL. VI 6- 1 .,

en I

"'

.... 0 r

< -

~ 3 PHA SE AC M6 !SA 12:· .

AC AVIONICS BUS No.2

:

HAIN DC AVION ICS BUS No.2

I SOLA TED AVIONICS

BUS

...X ISOLATED DC -:1 5A

AVIONICS BUS

DC AND POWER RELAYS fOR

ANTENNA SELECT I ON SYSTEH ONLY

\ No.2

No.1 TOP AND ANT(IfNAS

HAUUA.l. Arn t:IWA Elt:CTI OU

No.1

A 1 I< C H A r T

FLIGHT STATION CENTER CONSOLE

ANTENNA : SELECT I ON PANEL

CONTROL

TO INTERPHONE SYSTEH

No.1 No.2 -· ..... ()

No.2 No.1 ANTENNAS

IISTALLATIOU

UHF' ANTENNA (FOUR EA CH )

The tlu-ee position toggle switches on the antenna selector panel will deter­m ine the antenna used for transmission and reception. (Automatic antenna selection has been disabled.)

The control panel provides the transceiver with all the required operational data.

0

":"\ ·~ r;'\ .>:"\ ·--.s 0 ·~ v -~ n."'7'.k~o'> 0.., .-;.,.-. COn .. ''"i ,....,..,e ' \\' he" ·et ' 0 ":\-1 ' "'\.' '· ·lCt'V'"'~,... . t··~ ....,...., l " r e -!. ;;.;. ·, .::;.. . • • • • .. ---·t..: ..... .., t"'-'"" .. , '--• ::; \. ...... ~..~. .. . ) .:.. ............. ::- ....... •h- .... ..

ce :~: e!·. K~oh @ :1dju.:;ts ~~e v') .. un:e oi'" r.:e rece:vt!r a:.1C~ ... ~ t:--.e l:":ten:Jr,one system . T·::l ret;eive anc! transmit t::~ interp ;"~one :r~ :.'lr:; ~wi:-:- !: :nus t bt· StH

: .. ; :::c ·~·~:~ ~ys:;~ :n :)ei:-:; •Jpe!:":~ ~2~ .

.. :::e ::;Jin :-eceh·e: ~r:C cra:1s:::itte:- se~~:on.;; or' :!:e ::-:u;zcein: :- are :11w~:,·s tl!neo :o t~e selected f:::-equency . T~ree mod es of f:::-equency selectio~ are ·--,• sto• ~ ,.;.-. k~~b 0 :- - • '0' • • .. ... . ...... \:::;,; •

~.:.':.;:. ;..:r.oO@ ln ":.t..;_'\~.A L" po.si~.i.Vi: t~ae (fi :..::uobs ar~ a.:tivaLe~ pe:-rnit!.ing r.:anual f:::-equency selection. Do not selec~ below 225. Ou with ~he iive manual knobs.

The operating fr equency a ppears in the® windows . With the@ knob in "PRESET" position the ® knobs are incperative a~d the @ knob is in control.

The® knob has channel numbers, not operating frequency, appearing in the PRESET window. Twenty channels are available. (The operating frequency of

VOL. VI (i-3

', .....

each cha!l!lel may be changed from the bottom side of the co!ltrol paael.) With the @ knob set to "GUARD" positio!l the main receiver a!ld traasmitter are tuned to the "guard" or "emerge!lcy" freque!lcy. No channel or frequency display occurs i!l this mode.

J"he "BOTH" position of knob@ activates an additional guard receiver which is permanently tuned to the emergency frequency. Knob @ also affects the guard receiver volume. The operation of this receiver does not affect or is !lOt affected by any other operation of the control panel. However both receivers are disabled during transmiss;on. Both receivers and the transmitter are disabled during tuning. When the operator changes frequency or channels by any mode the transceiver tuning is started. Transceiver tuning is indicated to the operator by a 400 Hz audio tone in the headsets. When the tuning cycle is completed the tone ceases. Transmission is provided by pressing the inte:·­phone mic button and speaking into the microphone. Releasing the button pro­vides reception.

NOTE: K!lob@ must be set to position 10 for full transmission power. This knob's function will be discussed in detail in Specifications and Block Diagram Operati~n sections of this chapter.

With the tone button cover removed, tone transmissio!l is accomplished by pressing the button.

' • fj-.j

VOL. Vl

...... ·

SPECIFICATIONS

ARC-90 UHF RADIO COMMUNICATIONS SYSTEM

VOL. VI

CHARACTERISTIC

Number of Channels

Number of preset channels

Freque ncy accuracy and stability:

Main receiving system Transmitting system ( With external modem) Guard receiver

Channel tuning time

-:Frequency range

Channel separation

Carrier output power

Power outpl!~ control

Receiving system bandwidth (Internal modc:n ) (External modem)

Transmitting system bandwidth (Internal modem)

(External modem)

Main receiver RF gain

..

SPECIFICATION

3500

20 on preset drum I on guard channel

±s. 6KHz :!:3.6KHz ±sooHz + -5.0KHz

6 seconds (maximum)

225. 00 to . 399.95 MHZ

50 KHz

30 watts (minimum) internal modem

75 watts (minimum) external moc!e rc.

U - to $6- -:!!> atten­uation io !0 steps

44 KHz (minimum) at !:5 db 10 MHZ at :!:3 db

8 KHz (minimum) at :!3 db

+ 10 MHz at -3 db

25 db (minimum)

6-5

·· ... ..

SPECIFICATIONS (continued)

ARC-90 UHF RADIO COMMUNICATIONS SYSTEM

ij- (;

CHARACTERISTIC

Noise figure

Main receiver sensitivity (f.or 10-db S+N/ N ratio)

Guard receiver sensitivity (for 10- db S+N/N ratio)

Receiver Audio Output Power

Ambient temprature range

Maximum altitude

Equipment classification

Power requirements

\Varrn-up tiC"'.~

SPECIFICATION

6db

3 uv

3 uv

100 MW to a 150 ohm load

- 55 degrees c to +71 degrees C

70, 000 feet

MIL-E-5400, Class II

3- phase, :15 volts, AC, 400- Hz, 3A per phase

~ minlites ("~e:-atiooa!, :

i5 minutes tiul! ;:»e:-f~r­maoce)

BLOCK DIAGRAM THEORY OF OPERATION

Modules

The transceiver has ten modules. Below are shown the module numbers and locations in the transceiver.

..

MODEM-~~

(MODUI..ATOR ­

DEMOOULATOR)

DIGITAL TO ANALOG

CONVERTtR 1A7

T R A ~ S C E I V E R

MOOCL£ P!;RPOS£S

SUPPLY 1A1

RF' OSC I UATOR

1A2

The chassis is considered :l ~:,J~'l !E- . -r:~~ rt:rr.~ini::..; :-:i::c ~cd:..tl~s tl~~g i.!tO

t~1e c hassis for eiectri: a: ~:!:.e!"cor..:: t:c ~lOil :1::-j r.1 e c~.::i.:::c~i s:lp;:c :-:. ::~:. r. !r: ·~

;> lug- in modules ar t mec!:unical~y :.nC~peode!it o: tt:1c :1 vtl:er .

The chassis sen-% also as ar. o.:: chac.!le l a llowir.g i•) rc ed air coolin!; of :!le r.:odule,;.

T he power supply module pro\"ides !he r egu lated a.'ld unregulated A-C and D-C \'Oltag"s required by the transcei\'er and operate s on a 3-phase, -t OO nz., 115-volt, 3- amperes-per- phase input supply .

VOL. VI 6-7

POWER SUPPLY OUTPUT POWER TABLE

VOLTAGE (nominal) CURRENT (maximwn)

· 450 volta, DC 600 milliamperes (MA)

250 volta, DC 150 MA

130 volts, DC 150 MA

·za volts, DC (regulated) 500 MA

28 volta, DC (unregulated) 3 A (steady) 14 A (surge)

- 95 volts, DC 60 MA

26 volts, AC, 400 Hz 0. 9 amperes

6.3 volta, AC, 400Hz 3 ampe res (each output) (two 'outputs)

6.3 volts, AC, 400Hz 3. 75 amperes

The digital-to"11.nalog converter module changes digital data to tuning infor­mation for the tran.smitter, main receiver, and frequency multipiier modules . Tbe digital data is provided by the control panel a:J.d is a function of the se lt!c~ed f requency.

Tile RF oscillator module procuces two highlj· accurate outpu: !rec;ue::~cies of :. 9!:.9999 Mhz and 4 . :36363 :MH:t. This is accomplished oy two •emperature compensated crystal oscillators. These two signals are used as standard or r eference frequencies for the synthesiZer module .

T:1e synthesiZer module uses the two RF oscillator .:-e!erence frec;aencies and digital frequency selection data from the control panel to provide 3500 usable output frequencies. Each frequency is dependent on control panel frequency selection. These output frequencies are used as input to the frequency multi­plier module .

The frequency multiplier module multiplies the output of the synthesizer by a factor· of nine and increases the power level for injectiOn to the transmitter or main receiver . The frequency multiplier contains a servomechanism that automatically tunes the module. The servo r eceives tuning voltage from the digital to analog converter. The tuned frequency of this module is a function

.. VOL. \"!

of the frequency selected at the control panel. The frequency multiplier output is approximately one watt and is 60 MHz higher than the selected frequency.

The modem module modulates the transmitter with the interphone mic signal during transmission. This is provided by the modulator section. The demod­ulator section serves as the main receiver, 60 MHz IF amplifier, and detector. During reception the main receiver signal is amplified, detected and supplied to the interphone system. The transmit output signal, from the modem, is actually a 60 MH.z, amplitude modulated subcarrier. The level of this signal is 30 milli­watts modulated 95 percent.

The· transmitter module translates or converts the 60 MHz, AM signal from the modem to the selected operating frequency and provides necessary amplification to raise the power to a carrier level of 30 watts minimum. A servomechanism automatically positions the tuned circuits within a maximum time of four seconds. The servomechanism requires tuning information from the digital to analog converter.

The 60 MHz, AM signal from the modem is amplified and mixed with the UHF injection signal from the frequency multiplier. The difference frequency is the operating frequency selected at the control panel.

The main receiver module.amplifies the received operating frequency and con­verts it to the 60 MHz IF required by the modem. The IF output to the demod­ulator portion of the modem is the difference of the received frequency and the out{lut of the frequency multiplier .

A servomechanism automatically tunes the main receiver module to the selected frequency by using tuning information from the digital to analog cO•lVerter ,

The guard receiver module is a complete single-channel receiver for indepen­dent r eception of e::nergency communications on one frequency within the 23S. 00- to 24e . 00- M!iz range. 2-t3 MHz has be~n chosen as the eme.rgency frequency.

TP.ANSMIT BLOCK DIAGRAM

The interphone mic signal passes through the tone oscillator circuit to the audio amplifier A20Ql. The amplifier audio then modulates ll. 60 ;1/!Hz signal from an oscillator providing a 60 MHz, AM signal. This signal is amplified by Al9Ql. The modulated signal is detected by A2QI providing sidetone audio to receiver audio circuits, w hie h will be heard by the operator. The modulating signal from Al9Ql passes through the deenergized contacts of K6 in the chassis to the trans­mitter module. However the level of this signal is ''aried by the control panel " PWR" knob. This knob (switch) has ten power positions which affects the attenuator lAIOAl. However, only positions 8, 9, and 10 affect the attenuator

VOL. VI 6-9 . ' ..

0:

' <:

< 0 r

AVOID IM~T FROH IHTlR~MOM£ »YST£H

r---'··--­MODULATOR (~ur or

MODEN IA9)

r ·· .. L . -··-

ATl' l HUAT i;R (PAftT Of" f, Out: t:

ATTlUUAT OH

IAIOAI) '-· - - ·----·-· -

I'VW( U DATA f f(O t>l

t,;OtHU O L P AN(L

··- .. ~ _J

~r~:HS~ITTER -· (lAS)

NASHR

,r

OSCILLATOR SIQNAL

-------·

t UHF ~OW(R ATT£NUATOII

(PART OF P'OW(R ATTlMUATOII

1A10A1)

TRANSMIT-RECEIY£ -ANALOG TUNIIIG OAJA REC[IY(D

RELAY 1A10K8

OICITAL OAJ A f~OH CON TRO L f-' AU EL

OIC I LLA TOR (1.42)

II( SIGNALS

--- .. , -~ IDETON( S IIINAL ,

• l~~~~~~:~~(IV[R DEMODULATOR MAIM

(PART or f-- IIEC£ I YU

HOD(N 1A9) (1A6)

C. AUDIO I ,.,

LOCAL OSCILLATOR

· ~ SIQNAL

SYHfH£ (I A

---·-·-] "Z[R

J_l_ - ··-fii(QU[NCY TRANSMIT-- MULl I I'Ll (R IUCEIV£

(IA4) ULAY A101(9

0•/ E flAll BLOCK DIAGRAM

-

;

UHF Sl To/rRD+<

AUDIO

SieNA CONT

OUTI'UT L n IIOL

t

..

< 0 r

' < -

en I -

TO/fROH

ANT(NNA

1 VHf

OUTPUT

f I L l[R

TO MA IN AND r+ GAO AEC[IVCR S

~ AN T, CIIANGC

A CLAY

lA lOA I

~· ---UHf AN D

f.- S I DE TONE CAT(

AT HNUA TOR

TRAt•SH I T T £.R MOOVL[ 1A5 ·

ri ~ H I LE VI',t. , .. IPA - 60MHz AMP

V4 ~ NIX

V3 V2 VI

225 1A10K8j

T I S IOClON[ <;AI[ SID[ TONE

399. 95'*iz

8 ANOPAS$

• AMPS

Al01 ,02

. 666 31 -5 SY

], 105MH7 fR OM

NTH[S ll[R

I

TO 1A10K11

I GA H

PWR O£TEC TOR CON TROL

~ .--8 AN0 PA $S ~ f-t

f-. -~ AHP$ Tll l l'llR

.ut P TR II'L[R

A<!O I VI V2 ~. V3 f-e, V4

fA[Q HUll MODULE I A4 . -

M0_2~~ A ! .O!,_!..t._;:! !Y~- 0, f HOO(M MOOUL E 1A9

.. - I TON[ os c [3'~1z_}[ 60M:J

S IDCTON[

010-Put

AU

IN

f ROM I NTPH

S YS H M

A2101

r AUDIO A'"'P

A2001

'[M osc ,O ETE C TOR

70 1 A22 A2Q J l _T . ~ -- ~ TO A] 4Q]

RAN St<IITlj- 60MH! I H 1 A9 " ODUL[ i-.. ..oo .. Rf P\IR AMP

~!801 A1901

TRA N S ~! IT 0 L 0 C K D I AGRAM

285 459. 95MHz

~ t)R

R[LAY

1AIOK9

I 285 !Q 459. 95MHz

TO MAIN RCYII

PWR

CONTROL-ATTENUATOR

lAI O Al

IHT EXT

CONTR OL- TRANSW I TTER

I NPUT RElAY

1A10K6

I

.,., I -"'

:

.··•

fROM ANT A [lAY

I A I OK~8~~~M~·~I N~~·~c2v~R~M~u2oZutL~E~~I~A~b~zr.~ . ·.-~

H:(' V H

VUlPUT H (l.A'r

UHf AMPLS

YI,Y2

I I J. ' S(RVO

TUNING

..... 6() Mllz or AMPLS

v3 V4

'F .,

285-453. ·)5 H(

fHOM f R( Q MULT M00Ull

Rf ACC AMPL$

A16Q1

r-

Mf AGo( AMPl $

1501 ,0<' 03

INT ( XT CvttTR OL

60MHz fiLTER

R f AGC AMPLS

AI6QI

GU Ak P RC YR H00UL( IA8

• i'

MOO(M HOOUL( JA9 0( M00VL AT OA S ECTI ON

601-1Hz 1 r AMPLS

A30l,A501

NO IS ( LIM I TER

AIOI ,A4Q

Af MIX

A6QI

78 6MHz

osc

SQUELCH

Al201 , 02,03

SIO[TQ N[ fROM MOO S ECTION

If ACC

A 1101 , Q2

AUO I O PR[AHP & SQU[L (H

AU DIO

AUDI O

0[ HC TOA

AIOQI

AUDIO Alo4PS

KEY[R RELAY

IA7K3

SIOETONE

GATE RELAY

lA IOKII

li ( tf iV(Jl IJ l 0 C II 0 I A G R A M ( u H r l

S IDET ONE GAT£

VOLTAGE

(

( \ ....

at this point. This provides three power levels to the transmitter. The signal is applied to VI In the transmitter module and Is mixed by V2 with the output of the frequency. multiplier module 1A4. The frequency multiplier module will be further discussed in the Frequency Generation Block Diagrams section. The output frequency of the lA4 is always 60 MHz above the selected frequency, thus XXX.XX MHz + 60.0 MHz = lA4 output. Example: 225.00 + 60.0 = 285.00 lvlHz.

Tlre output frequency of V2 is the selected frequency and is amplified by the Intermediate Power Amplifier (IPA). The V4 (PA) output is detected by the side_tone gate detector. The output voltage of the detector passes through the attenuator to be adjusted by the "PWR" setting from the control panel. Since the PA. signal level is changed to three levels by the "PWR" control the sidetone gate voltage will also have three levels. This is undesirable for the side tone gate relay lAlO Kll which must have a relatively constant voltage regardless of "PWR" setting. This is corrected by the attenuator adjustment. The sidetone gate relay (Kll) in the chassis (lAlO) provides coupling of the sidetone audio signal to the interphone sy,stem only if the transmitter power output is s!U!'icient for a given "PWR" setting.

The UHF output of the PA passes through the attenuator for the seven remaining steps of the "PWR" setting, thus there are ten power output levels. The L'1iF signal then-passes through the energized (trllllsmit) contacts of IA!O KS antenna relay to the output (low pass) filter. This is the final output to the antenna.

GUARD RECEIVER

The 2-!3 MHz signal passes from the antenna through the deenergized (!'eceive) L~lOK8 to the guard receiver module . Wi:h the fu~:c:iot~ k!:!oo on ' 'BOTH'' . (gu~rd receiver •)n) the signal is ampliile<! by A:2 Vl ~nd V2 and mi..xed wit~ 196. 2 ~1Hz from the ~riple:- AiSQi. Ti~e ou~;>ut '.)[ A2Qi (lBr. !.?) is ~G . :;, :.ai:: ::~·:,~ the i.oc~l oscEla:~r. Th~ outpllt of A5Q~ ·2::-:! ::: : is :~.5 ).Hi .t :1::r:: L~ ·J.:~:.;i liicd oy fen:.!' sta~es . T ::~ :t.-...;C: i~ ~j~:e!" .. : ~·=- .\!0\~; .: .:~::1JJ::!3.:c:~ : : ~e :: £!~"7' . .:;.: .

:· .. c d~t.cc:ed al:d:J f:-v :n Ai .~~l ~as f·j~~ ~.;g:-.;;.: ;:>at~.::i. T:-tt~ a·.:.dio o~~~;~.;:. :e \·el C•)ntrois the RF AGC circ\<its which in :urn reg~iate the gam of the R::- ac:;: ­l!!lers A22 V! and \'~. T!':e audio outpt:t lev('! aiso contro ls t!te IF 'AGC cir-

T:~e audio output signai yass~s tnroug!t the :"..O lS~ ~inuting ~i!'cu.it.s Al~..<i :1nd A2Qi to the audio preamplifie r A14Ql. This ;:>rearr.pli:'ier is only :ur:1ed on w!len the audio output lefel :rom Al iiQl is sutiicie 'lt ~o operate the squelch circuits Al2Ql, '-'2, and Q3. with s!Uficient leve! the squelch circuits tura on Ai-!Ql permitting the audio signal to pass. The audio level required to opera:e !he squelch circuits is determined by the GUARD squelch adjustment on the f:-om panel of tnt transceiver. The g:.~a.:-d aL:di:.J signal passes from Al4(0<1 to Al91,il. The main audio also passes through Al9Ql. A19Ql is operative also in the ''MAL'!" position of the control panel function knob. The guard audio sigt:.:ll

YO L. ~'1 6-13

is amplified by the audio power output stages, muted during tuning by 1A7Kl, and is coupled to the control panel. The volume control varies the audio level to the interphone system.

MAIN RECEIVER BLOCK DIAGRAM

The O_l>erating frequency selected at the control panel passes from the antenna through deenergized (receive) 1AIOK8 to the main receiver module. The signal is amplified by VI and V2 and mixed with the Frequency Multiplier signal. The V3 output (1st IF) is 60 MHz and is amplified by V4. The lst IF signal is coup.led to relay 1AIOK7 in the chassis. The 1st IF signal passes through the deenergized contacts of the relay to a 60 MHz filter in the c hassis. The output of the filter is connected to the modem module. The 60 MHz IF is amplified by 1A9A3Ql and mixed with 78.6 MHz. The output of A4Ql (2nd IF) is 18 .6 MHz and is amplified by three stages.

The audio detector AlOQl demodulates the IF signal. The detected audio f:-om AlOQl has four signal paths. The audio output level controls the RF I AGC circuits which in turn regulate the gain of the RF amplifiers lAG VI and V2. The audio output level also controls the IF AGC circuits wbich in turn regulate the gain of. the 1st and 2nd IF amplifier circuits. The audio output signal passes through the noise limiting ci rcuits AlQ! and A4Ql. This preampl ifier is only turned on when the audio output level from AlOQi is sufficient to operate the squelch circuits AlZQI, Q2, and Q3. With sufficient level the squelch c ircuits tu:-n on Al4Ql per mitting the audio signal to pass. The audio level required to operate the squelch circuits is determined by the MAL'I s quelch adju.stment on the front panel of the t:-ansceiver . The main audio s ignai pa s ses f:-om Al-iQi to Al-tQ2. The main audio signal is ampl ified by the a•·dio ;>owe r output s tag~s

Al3Qi a:::d ~2 . T he mai:l audio si.gr..al ieave s ~e r:::oden: :lll~ i s cou?led to <.'I.! OK:; . :-::e deene rgized conta cts of !<:l ::ouples tte ma in audio :~~·.;;h t !-!e deenE:=gi::e:! \:-~ceh·e 1 1~7S:3 to the g'J.:!:d : ec e!Ye !' ;!.:.!Cio ~Lxe :- . .:...lSt~ l. :-~.1.,; H~~ 3.~~0 1"<: ­

~~ ~':es a -:C·O Ez :.o~e :':c~ ;,.A 7K!! d::.r:og t;.:_"l:~g . Th ~ tuc.e ·tone :·r c:a.:.~ a:_ilio s igna! ::ow passe s t!-..rough the sa.:ne c ir cuits a s discussed in :.';e Gu~:-c .?.ec,;,1ver Block Diag:-am .

D~;.ring tr a nsmit :he detec ted 3i<!etone s ignai passes thr ough the rccdem a udio cl:-cuits. The modem output to lA 7K.3 is routed to the sidetoce gate relay !AI OK!!. If the t ransmitter power output is sufficient for any given "PWR" se tting Kll will energize coupllng the s idetone audio to the guard receive r audio mixe r 1ASAI9Ql.

FREQUENCY GENERA TL'\G BLOCK DIAGRAMS

The entire discussion of the main receiver and transmitter was based on

1)- l ol . ,

·· ....

assuming the correct output frequency of the frequency multiplier module. The following discussion will show the frequency multiplier output.

Three modules are reqvired for frequency generation; the RF oscillator module, synthesizer module, and frequency multiplier module.

To sll.Jlplify this discussi<>n "MANUAL" frequency selection at the control panel will be used.

The Frequency Selection Block Diagram shows each knob (digit) controlling switching fl!nctions in the high frequency filter section, low frequency filter section, 12 MHz oscillator, and relay lA3Kl.

The l.lllllllll MHz signal from the RF oscillator module provides a l.lllllllll MHz spectrum in the outputs of A4Ql. The 4.136363636 MHz signal from the RF oscillator Module is multiplied by 4 (16. 545454544 MHz) and mixed by A3Ql with the spectrum. This shifts the spectrum up to a usable range. The usable spectrum range is ten simultaneous frequencies in l.lllllllll! MHz steps from 22.101010101 MHz to 32 . 101010101 MHz. The high frequency filter selected by ::he 2nd digit will pass only one frequency. HF MHz s 22.101010101 + (l.lllllllll x 2nd digit). Tlle l.lllllllll MHz signal is also divided by the low frequency harmonic generator.

This generator is a series of multivibrators producing O. lllllllll MHz square wave to mixer Q3 . Since this signal is a square wave its harmonic content will be rich thus a 0 .lllllllll MHz spectrum. This spectrum mixes with 4.136363636 MRz s hifti:Jg the spectrum to a usable range. The usable spectrum range from Q3 will b~ r.en simultaneous frequencies in O.lllllllll MHz step, from -!. 69191&191 :IIHz to 5. 691919191 MHz. The low frequency filter selected by the 3~d digit will pass only one frequency. LF MHz = 5. 691919191 - 6 .lllllllll x 3rd c:ig::. The selected low frequency modulates the 12 MHz oscilla;or sig~l in ': a i:l:lced modulator :--io. : . '!'!-le Ci.f!erence (LSB) frequency is passed by t!:le ca;!d ;>ass ::iter. The -tth and 5th digits toge:he:.- chooses the crystal frequency for the osci!!ator. FM Hz= !2.479797979 (4th an~ 5th digit x 0.005555555).

" The low frequency signal modalates the amplified high frequency signal ln balanced modulator No. 2 and sum frequency (USB) is used. This signal will be amplified by AlZQI and Q2 whee. the control lst digit is 2. This signal is couplE!d to the frequency multiplier module. When the 1st digit is 3 the balanced modulator No. 2 output i s coupled to balanced modulator No. 3 where 11. Wllllll ~!Hz is added. T!lis 3ignal is thee. amplified and sent to the frequency multiplier module.

" PRESET" or "GUARD" frequency selection provides the same type digital data for the synthesizer module. The frequency multiplier module amplifie s and multiplies the synthesizer out;Jut signal by 9 providing the transmitter module

.. 6-15

"' I -""

..-: 0 !""'

..-: -

HIGH FR £Q HA AH C[N

A6QI

8Al HOO NO. :1

AI OQI,Q2 All

.. .. A3Ql A4

5TH THRU 14TH AIOI ,02 A2

HARMONIC

4 . 136363636Mflz f ROM ftf OSC MODULE

-o 1. 111111111 ~ltz fROM 05C

MOOUL[

4. 1363MH:

PULS E SHAfi'(R

01,02

s YN Tit (S t Hk, _>!2!!UL[ I A3 ----·--- --------------,

Hr MHz : ~2.10101010 t

( 1. 11111 1111 X 2ND D t Q t T)

HIGH fREQ

(ILT(R SECTION ~-~---4'----~ A5Ql ,02

ru rHou ruo '

AMPLifiERS

0 10 011 01

12MHzt

rMtlz = 12 .479797979 • · o!>'55oo5!o5]s~c--

IIAL MOD NO. 2

013 4

K1

~ 2

lsr

c "' ..

D tGtT COH TrR~O~L-~--,

II .. ...

At-4Pl

A12QI ,02

31.666 51 . 105MHz TO fR(Q

MULl MOOUL(

LOW fAEQ .... ~.J-IIUH G[N

A1101, 02 AI8Q1, 02 A1 9Q1, 02

. (4 AND; DIGIT xO. O

l. U\4 fR(Q

II ITRS fl11~-----~---~ IIIRU f L20 I

IIAL MOD ~< o. I Q8 09

BAND P ASS

fiLTER

A2001, 02 r Mttz: 5.691919191-(0.111111111 X :lR~ OtGtT)

f U [ 0 U E N C Y 5 ( L ( C T I 0 N

....

· .... ..

and main receiver module with the injection frequency they require.

285 TO TRANSMITTER.

459.95MHz T/ R

TO MAIN RCVR RELAY 1A10K9

.. BANDPASS BANDPASS AMPS - AMP'S ~ AMP - VI V2 A 1Ql ,Q2 A2Q1

I fREQ MULT MODULE

fROM SYNTHES I ZER 31.666666666 THRU 51.5555555MHz

TUNING SYSTEM

285 459MHz

f'MHz: SYNTHES I ZER OUTPUT X 9

r- TRIPPLER t--o TRIPPL£R

f-a-V3 r-- V4

1A4 I

The transmitter, frequency multiplier and main receiver modules must be tuned to the proper frequencies according to the control panel frequency selection. These modules tune in 100 KHz steps. (50 KHz tuning is not necessary.) The digital-to- analog converter module changes the control panel digital date to 400 Hz output voltages. Four output circuits of the converter couple these voltag~. to the three tunable modules .

The control panel lst digit (3) operates the converter lst digit relay providing 28 . 75 volts, AC to the first digit inputs of the three tunable modules. When the lst digit is 2, no voltage is provided. The control box 2nd digit (0 - 9) operates a mechanical digit seeker in the converter. The seeker positions a voltage selector switch (10 positions) providing ten possible voltages (OV thru ;;!. 75 VAC) to the 2nd digit i nputs of the three tunable modules. The 3rd and 4th digit seekers and selectors provide the same ten voltages to the 3rd and 4th digit inputs to the tunable modules.

The four voltage inputs (for a given cont:'ol box selectiot~j are su::J:ned io summing r e s istor networks in each tunable module. The surr.:n~:d 1·oitage to the servo amplifier has 2000 possible voltage s . However, the mechanical tuning limits of the tuned modules ;:>ermit only 1750 tuning points corresponding to 225 to 339. 9 MHz. Tho; servo wiil drive in the pro per direction until the :m!! "pot" is positioned to the proper point providing an out-of-phase voltage amp­litude cancell ing the summing network voltage. The servo motor a lso positions the tuning components in the module.

voi... vr .. 6-17

.•.. ·

DIGITAL TO ANALOG CONVERTER MODULE 378.9(EXAMPLE)

ONE OF THREE TVN~8 t. L

MODULES

'

' 4TH DIGIT SEEKER I ' l._l y:

.---'VV.;--:;.5..;,.1 ,;..• 7;.;:5..;,.v..:..; --6

51 75v

: . 46v .

i ~~=f=f=tii~l=~~42_;0.,£2~5vJ ;3RO DIGIT

SEEKER I

-34.5v

-. . . ~~m=A=ru:!~J '2NO DIGIT

SEEKER

200K

TUNI NG I 28. 75v l

CAPAC-~ I 't"'l

J I I

ls~ OJY I T

9

;

I i ' I I I I

I I i :

' I I i 8 - 0 !:{

'T ~ ·::;r~ ~ L-r------

··1-"""'w~---+----------' NULL POT.

' ! I i 4

57.5V AC cu-:- or PHAS~

T U N I N G S v S T E M

6-18 .. VOL. \'I