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CP400 SERVICE MANUAL COMMUNICATIONS POWER, INC.

1. 170 4 AUDIO GENERATOR HEATH MODEL IG 18 approx 100 CP 400Detailed Circuit Description 1 Method of Frequency Selection The front panel switches SW806 and SW807 provide binary coded decimal BCD outputs corresponding to each digit of the channel number selected BCD coding is as follows for each decimal number Number C8 H H O0000000o O O O0HHEHOOO ols 0 OO H HOO L HOOIMN Q HonornomrorolhH O O J O Q QO N F O Cl C2 etc correspond to the l s 2 s etc place in the binary equivalent of each diqit of the channel number Note that each decimal digit is binary coded not the entire number Cil C 2 etc are the bits of C the first digit in the chan nel number Col C52 etc are the bits of C the second digit of the channel number For example Channel 23 is 2 3 OS age L4 d ddd C18 C14 C12 C11 C48 cha C42 cil where C 23 E 5 8 i 2 3 Also note that TTL negative logic is used for the channel switches O 2 5 to 5 vdc and 1 0 to 0 6 vdc The radio operating freguency is determined as follows fy 27 500 MHz N 5 kHz where fg operating frequency N synthesizer divide ratio N 15285 N is a three digit BCD number N4N N4 determined by feeding the channel switch out puts into U600N for N and N and Nl control circuit for Nj U600N requires neg ative voltage for proper operation This is done by feeding a 50 kHz pulse from the synthesiz
2. SMO 7HOIS 5dbm 5On AM TRANSMIT Gi ea RF OuT 37dbm 50 AM TRANSMIT J102 OO J202 RX IN REPA 7HOI7 Oy ss 4 m E gt N oj ka gt d S S wp were gl e m S o e e Q Q e e z x 9 gt gt gt gt gt gt gt N 9 n n o o O o ix 9 v i D u 9 m jar m n m gt l S 5 3 Bl ml Ei 31 di 2 gt X o S xl zl z SI x 8 a S o 5 S l S SI z x E gt Q gt lt iz D x o gt ky Ka Ke lt m o N N N 2 lt o o o o o o lt a 8 17 13 See NOTES 2 EEAKER L 2 I I ALL MESUREMENTS MADE IN RECIEVE MODE UNLESS OTHERWISE SPECIFIED E 2 INITIAL CONTROL SETTINGS 3 3 POWER ON N 5 AUDIO PAQUT SPKA ca O INTERFACE 7H020 Mi AM MODE O O VOLUME SQUELCH CLAIRIFIER AT HALF ROTATION Olou 6 0 AUDIO PA iN ovog 0 REAR PANEL CONNECTOR U COMMUNICATIONS POWER INC 2407 CHARLESTON Rd MOUNTAIN VIEW CA 94043 eme TINOV 76 Dem INTERCONNECT CP 400 MODULES DRAWING NUMBER 26C002 2 SPARE ti 8 TALOVOC 8 f Eng PRINTED DN NO 1000H 10 CLEARPRINT AUDIO PROCESOR 7HOI8 10 10 Kai O 47 109 A606 gt Elyn SMO BUFFER 47 s vco Ol 1000 SYPC reos LOOP FILTER eur od 32 Aen t o O 1000 10phy ooed 160 1002 rd C614 REIS 1604 do NEO ceo T 1000 020 x
3. gt COMMUNICATIONS POWER INC 16 5 2407 CHARLESTON Rd 9154 MOUN TAI CA 94043 I 45vpc Tx eae Cd oraw MSS Rx MUTE q m y s em fi C275 FACTORY SELECT SQUELCH AMP RX TX CP 400 CP 2000 Ovoc H i N T DRAWING NUMBER DC SGUELCH OPEN E REVISION 7 STARTS CP 400 120016 10 42434 PWINTED ON NO 10008 10 CEA Raa OUT a 13 voc 3 J 6voc c Ki rifo LI02 4 STII 33 cue ROEE LN T 102 ORNER 22 RIOS ci MPN3412 0105 vr 4 WT C109 DENOTES FRAME COMMUNICATIONS POWER INC 2407 CHARLESTON Rd MOUNTAIN VIEW CA 94043 ra lt jo RF POWER AMP CP 400 ni we een tym PRINTED ON NO 10004 10 CLEARPRINT PADE OUT SMO 4 x S REC MUTE DCLARIFIER N AM SELECT o PTT OUT lt AM MODE 5 iOvDC amp XM1T AUDIO x USB MODE x PTT IN E BC ss Swaoe IN9154 0802 0808 MPS5172 CLAKIFIER 10K RBIE MPS5172 0805 FN 17 VDC TX a MPS5172 Gar NN m pe N4154 0863 1 S RF R u METER 0 2ma amp 2 ago ZPR Ag AE OR en E ad Selo Mes ah MPSE562 22K 1000 R807 R808 47 1 13 6 SWITCHED 2 SPEAKER I 3 13 6VDC INPUT 4 PAOUT SPEAKER COMM 5 SPEAKER 2 6 GROUND 7 AUDIO PA IN 8 v T 9 METER IO MOD LITE AUDIO PA 10K R806 sw802 O VOLUME N B COMMUNICATIONS POWER INC 2407 CHARLESTON Rd 9 4 SL SPEAKER MOUNTAIN VIEW CA 94043 O 6363 0 0 90 wann
4. L606 C642 0611 output is low pass filtered by C623 L605 C624 and converted to TTL level pulses by 0615 0615 output is applied to the program mable divider which consists of U600G N3 U600H N2 and U600J Ni The program mable divider output is applied to the phase comparator U600A and U600B which compares the pulses with 5 kHz output of the reference dividers U600E 16 and U600C 10 The output of the phase comparator is level shifted to 10 volt pulses by 0613 Note that the phase c mparator output when the loop is locked consists of 5 kHz square wave the duty cycle of which is proportional to the VCO dc tuning voltage required for operation at the given frequency If the phase comparator out put is at O or l logic levels and does not have a pulse output the loop is not phase locked The pulse output of 0613 is filtered by C603 C607 L601 and L602 to produce a smooth dc tuning voltage for the VCO R607 R609 and C608 form a gain compensation network to assure loop stability 7 Bro Two crystal oscillators are used for the BFO The 10 200 MHz 0606 is used for AM and LSB The 10 197 MHz oscillator 0202 is used for USB only Both oscillator outputs are low pass filtered by C664 L607 C665 and amplified by 0607 The output of 0607 is fed to the double balanced mixer module D610 D613 which is the product detector for SSB receive operation and the balanced modulator for AM operation R699 and D614 form a network reinsertio
5. oi 2700 Na 0609 R607 moe 6609 zopf 20pf R639 7 018 C616 17VDC 1000 3 6605 R601 gt dos T 100 2 MY2DS Z 9 4 po 01 270 dy 213224 i css neba peo t S er R645 IOK A f Zerf A602 b IN4154 Ossvoc i D602 a vod 10 104154 f Q 0603 J C svoc 100 0 R629 C620 gt 4700 Se ce25 o PROGRAMABLE b W I d ur Bi 1000 ad USB OFFSET OSC DIVIDER Ces Sv0 1650 4999 TN neas c ox nese spf zas 68pf A Svoc 52 NI a hes sio I 44 4 270 o San ce28 e vw RES OK 2 0637 W Lk Rise MPSSI7 4 340 12 803 te or i 270 12 LUC 3900 2614 C XLI Set 633 R638 SP RR c ro 270 i a 1 2000f i R655 26 spf Lis vec P spf S00pf 2470 cds D A646 12phy 25pf L 1606 25 C642 280 E A erger 10 O TP6 100 100 3900 REES 664 200er 1 6095 3 R667 Essi O IDK ced svoc oo R660 220K 7 8VDC O 3VP PAN iso R659 Ages QK 4 IOK V mv spr 2 2opf 12 B00Mhz Nas 7 C646 R68 06 C647 C648 XL2 4 16K is 7400 p 22VDC REFERENCE OSC g 7400 D 100 820 Ol 6660 R688 R668 USB OSC 1000 I6K o Rage RES C66 10 19 7Mhz Agee 4 9v0C XL3 0 A Q ceso MPS HIO CH 4601 iF OUT 200 20pf i 2 20pf 10vDC Geer Lee c666 T c667 500 470 ae TP O 4602 RF OUT R689 Oprisver A 100 MPS 3412 1000 MBDIO R697 004 R698 BUFFER r NE ae r2 rs C671 C672 OzP Is AM COMMUNICATIONS POWER INC AM SELECT 2 2407 CHARLESTON Rd MOUNTAIN VIEW
6. IF gain For SSB operation the output of 0213 is switched by D211 into the product detector BFO 0214 is the AM and AGC detector 0216 is connected as a temperature tracking diode to bias 0214 The output of 0214 is low pass filtered by R309 and C288 to provide dc voltage for AGC operation This ac and dc component is applied to comparator U200E R306 sets the comparison voltage for U200E The output of U200E drives follower 0212 to pro vide fast attack of C277 R297 and R298 set the AGC decay In the AM mode R298 is shorted by 0217 which shortens the decay characteristics of the AGC R283 and R281 apply AGC to the IF amplifiers U200C compares the IF AGC level set by R292 to be gin rf AGC R289 and D208 assure full receive rf AGC shutdown during transmit Q208 is the PIN diode D105 driver U200E senses a dc IF AGC level set by the front panel squelch control R809 to open the audio squelch gate Q215 0219 is a FET switch to select either AM or SSB audio for amplifier U200F R314 is to balance AM SSB audio levels into U200F The output of U200F goes through squelch gate Q215 to the output amplifier 11 Detailed Transmitter Operation Microphone audio is amplified by Q501 and is followed by U500A which is a high gain low distortion amplfier When overdriven the output of U500A symetrically limits the audio level applied to the compressor which prevents overmodulation C505 and C508 determines the amount of audio pre emphasis introduced
7. Q COM 8 gt tet 5 Yu 5 eee NOV 76 EC o lt x LS 0 a Se 2 q PROCESSOR a ta INTERFACE CP 400 ST 9 ZA 3 F 5 E sm q S 6 REVISION 2 STARTS CP 400 12 018 3 lt N z 17X2Z PRINTED ON NO SOGOH 16 CLEARPRINT AUDIO PA OUT Q 13 6 sw rcHeo p U 22pf i 6425 AUDIO PA IN METER 9 TX METER AMP vr 8 M ure 22K R402 SPEAKER INTERFACE SPEAKER 2 001 C416 ted 4 3 o 2 SPEAKER 2 SPEAKER I CH PRIYGO ON MO 10004 10 CLEARPAINY PAGE OUT preanp HU our MIC PREAMP E cs 4 4700 2 c501 A301 f 42K 2308 R502 I c502 XMT AUDIO LEVELS TAKEN WITH 20mv IKC AUDIO APPLIED TO MIC CON COMP our 6 AUDIO AMP 1220pf 2N 546 C403 0403 a JOK LD n os 220K R404 SPEAKER sa 00 00 C417 6416 x 23 5MHZ NB AMP na sw i2 me RS 001 T501 0514 3900 R325 25pf A gt Wm Oi K Q812 1000 MPS HIO LIVE R524 10 REG 2 A546 REG COLL 04 ta R54 N f RES BASE 0 1994 2 PS 6502 4700 C524 I 100 0514 B R551 R544 A 200 820 10pf Ir EE R548 cats T 200 13 6 Sw 12 d MG 1723 1000 ACTIVE AUDIO D F EB voLTAS R549 LOW PASS 300 TM IOK 6200 FILTER ren 42 Va R545 R550 Yn cs26 3A 170 4 GROUND 5 0 VOLT REGULATOR ALP OUT ven PANTER ON NO pn 30 LEAST 47 R533 100 IOK UE Md s 4 MPSMO 3900 ph
8. also is passed through buffer 0203 to the gate of the transmit rf mixer JFET 0204 The source ofQ204 gets LO injection 16 3 MHz from amplifier 0206 The out put of 0204 27 MHz is bandpass filtered by C205 C209 and L202 L204 0202 is the exciter output amplifier filtered by L201 and C294 matched by C201 to R205 R205 sets the rf drive level to and therefore the rf output of linear transmit power amplifiers 0101 and 0102 0202 and Q101 are operated class A with LC and transformer interstage matching respectively Q102 the final rf amplifier is operated class B with quiescent dc bias set by R108 and temperature tracking diode D104 0102 also uses transformer type input and output matching The output of Q102 passes through a seven section low pass filter which insures complete removal of undesired harmonic energy The rf output of Q102 is detected by diodes D101 and D102 and the resultant dc level is applied to the meter driver circuitry 12 Detailed Noise Blanker Operation The CP400 uses a tuned RF receiver operated at 23 5 MHz as a detector for noise pulses free of 27 MHz signal interference 1501 and C527 provide the front end selectivity of NB receiver amplified by 0512 and 0510 0508 is the noise detector which is class B biased by Q511 connected as a diode The output of the detector drives one shot 0509 which provide 5 10 micro second pulses to the NB switch 0224 on the R T board 7H016 L214 C296 C292 L211 C258 and C259 on
9. mode type with an AM mode centered at 10 200 MHz and an LSB mode with the carrier at 10 200 MHz For USB operation it is necessary to shift BFO operation down 3 kHz to the other side of the filter 10 197 MHz so that the filter will pass the upper side band If the BFO has been shifted down 3 kHz for USB it is necessary to shift the SMO LO input 3 kHz to maintain a constant channel frequency This is why two oscil lators 12 800 MHz and 12 803 MHz are used in the synthesized master oscillator SMO 10 Detailed Receiver Operation C113 L103 C114 L104 C115 L105 and Cll6 provide a low pass filter from the rf input connector which is shared with the transmitter From the low pass filter the receive rf input is coupled by C112 to D105 D105 is a PIN type diode which acts as a shunt attenuator for rf AGC on receive and as a snunt snorting switch tor transmit oper ation C250 C251 C252 and L209 provide the required impedance transformation for the grounded gate preamplifier 0223 L210 C255 resonate at 27 MHz on the output of 0223 This output is fed into the gate of JFET mixer 0201 The source of 0201 is fed with local oscillator signal by 0206 The 10 200 MHz output of 0201 is fed through diode switch D203 to crystal filter FL 201 For SSB operation lOvdc is applied through R245 to FL201 to change the filter to the SSB mode The output of FL201 passes through diode switch D205 and is ampli fied by U200A and U200B about 100db of
10. power out put on CH 20 AM Adjust R205 to maintain 4 watt carrier output Check output power balance on Ch 1 20 and 40 If this power varies more than 0 5 watt from Ch 1 to 40 complete the following Slightly adjust L204 for maximum power on Ch 1 and L205 on Ch 40 Check power balance Re check 4 watt level and adjust R205 if required Set front panel meter at 4w carrier with no mod on AM CH 20 using R412 TX MTR CAL on Audio Power Amp board Remove audio generator and using microphone check whistle and speech mod wave forms on AM LSB and USB Be sure AM carrier level is 4w and adjust R699 CAR ADJ for 90 whistle mod on AM if necessary Check whistle up power on LSB and USB 10w min Also check proper meter operation on all modes The meter should always go upward with modulation Check xmit inhibit on channels 41 and 99 Recheck 4w carrier level on AM adjust R205 RFD if necessary A AUDIO PROCESSOR 7H020 BOARD COMPONENT SIDE V ADJ a IOV SET o TP7 MIC amp SMO 7H015 BOARD COMPONENT SIDE B SMO 7H042 BRD COMPONENT SIDE CAR ADJ O TP IF SYNTHESIZED MASTER OSCILLATOR LEAD BFO 10 2Mhz EA LOW ose PHASE LOOP LA BALANCED DETECTOR BUFFER FILTER COMP vco MODULATOR m 10 i DC DIVIDER 5kh Reo CONTRO wa R609 6 C608 Q608 0610 U600C 10 197Mhz CSC 16 PROGRAMABLE Low DIVIDER DIVIDER PASS pj 4420044222 77 ee ee FILTER I AUDI
11. the R T board provide se lectivity and time delay in the main receiver 10 2 MHz IF after mixer 0201 The time delay of the main receiver path is necessary for proper blanking by the NB receiver III CP 400 TUNING PROCEDURE General 1 Be sure to tune the radio in the sequence given It is imperative that the 10 VDC regulator and the xmt audio processor be adjusted before the rest of the radio is tuned lt 2 Remember that a second class or better FCC radio telephone license is required to make frequency or transmit adjustments on the CP 400 3 On the CP 400 microphone connector a audio hot is on pin 1 b audio ground shield is on pin 2 c pins 3 and 4 are shorted together for transmit 4 All receive rf generator inputs are applied to the radio antenna connector 5 All transmit measurments are done with a 50 load connected to the radio anten na connector through a good quality wattmeter antenna onnector 1K apply kw oscilloscope for modulation d measurements 100 here Kmicrophone 10w kw connector min d rating audio generator AV CP 400 AUDIO PROCESSOR TUNE UP 7H020 Board l Set 10 VDC at TP 7 reide of C525 using R551 V ADJ 2 Set R570 MIC at full CCW counter clockwise rotation 3 Check that audio output TP5 clips at about 2 6v p p for 100mv p p IKC audio in V VI CP 400 SMO TUNE UP 7H015 Board ls 2 353 4 5a Set R699 at 4 rotation CHECK f
12. 33 F 100 I BFO MPS5172 TX RF BUFFER R244 109 TX RF BUFFER IF 0224 Ran RF o 100 FT 1500 cen A995 E 220 LEVEL R246 C2I5 R240 i 5voc R270 0 MPS HIO RX MIXER lt MPS HIO ME MPS HIO Geen Se 47pf J310 PRA Nia 0205 a222 01 c229 0201 390 1 1 VDC C267 R241 c223 oi IN 4154 asa IT 1000 R275 c300 V R242 C232 R270 C262 o j 6237 R239 A990 100 v 7 SMO BUFFER R331 A IN4154 j or l Reovee 0212 OI 2 ki METER C238 T C239 T 100 MPS 5172 IN 4154 A f IOVDC a220 Rea NESTOR T la er 11 z588 Gov ssa AM Ga 6ROUN S DETECN S METER S METER AMP AZ ECTOR D205 GROUND j ca o OK 1000 R262 RX RF AMP naes ISpf spf J310 JOI C250 C252 a 223 SSES J202 4r PoE RX IN EN VR 29voc h N 1809 3412 25pf 820 0212 c25i oo 1470 p nate c288 Bd MS BR RA a j C256 01 o u c312 261 L 6260 ji SE mae STD TEST CONDITIONS PN A E Lsvoc 10 VOC RECEIVE CH a EE e AM MODE 5Odbm RF LEVEL NO SIG 5VDC TRANSMIT CH Z 95 AM IKhZ AM MODE Tx 8VOC RF AGC AMP JOK Moos u AF AMP TP5 R289 GER 220K 25 O MPS 5172 sa CH R319 N H li R287 x cM Q2 MPS5172 er TP8 gt FE IER 22pf IN 4154 a212 IN4154 IN4 54 O R318 C290 0208 a amp PVDC D209 D213 2N 5461 W SIG 5 1 VDC Q215 YR aa BOZE Bor PEAK DETECTOR 10K i G 6VDC NO SIE ere C 9VOC W SIG R3I3 2200 28546 R298 RF AGC HOVDC m 0vDC 22K A294 veo o MPS 5172 u D 5172 200g 0225 0218 E aan AM R593 SELECT 1 2 V NOM 3 4 SQUELCH 9 zz e io
13. CA 94043 AM CARRIER R699 DATE AM MODE 5 AM LSB OSC MOD TOR 18 OCT 76 vee SYNTHESIZED MASTER QSC CP 400 DRAWING NUMBER REVISION 2 STARTS CP 400 PTT GUT 6 I PIT zum ren OM MO 10000 10 CLEARPTIMT FADE GWY O 10 voc PEAK DETECTOR 14VDC ead 10 1 R320 AE TX BAND PASS ER TX MIXER A AA Ges 23P 2 7P 55V iopf L Al 0885 A257 SVAP E etc C206 C208 p 244 NOM lo Vut 26 o 22K R230 cass Orov ais LEOIR e C247 1000 1 0 O 1000 0 ING 154 10K R224 E ja __ R255 liche ER 1 y KE R221 C220 0202 R223 A i 220 0 2 vo 7 R228 7 Z O 4vDC TX 90 AM gt R346 C248 75pf9 ER N S 2200 BVDC BL AL c205 0201 A MPS5i72 Ve R232 Nis 1 i MPS HIO 10K 001 6 MPS5172 2 MPS 8000 i _Q207 R222 Tc22 fovoc SES 0210 47 EV De J 0225 hevoc L 2200 465vDC ING 154 c243 680pf S i agx TX iopf 1000 0204 4700 C29 a R R i 270 Ol R226 90 R231 R256 v IVRP R220 Jezis R227 R229 90 c223 Ve e BUFFER osvoc VERY ERP ZC i DRIVER 5 N 0 6 VDC 12034 0209 R342 y VR O 390 o 47 Q 1 01 i 100 47 sel N C204 R344 d c2 gt 93T R343 9 C272 TX BUFFER C233 r R203 I I ALC DETECTOR COMPARATOR ER J206 I i n AVPR OI7Nhz 2 75V0C TX FROM NB Om VR BS E R207 NB SWITCH 22K J205
14. CP400 SERVICE MANUAL COMMUNICATIONS POWER INC LI LIT IV VI VII VIII O J O URUN m GO tjJ J O O DJ Pp TABLE OF CONTENTS RECOMMENDED TEST EQUIPMENT LIST DETAILED CIRCUIT DESCRIPTION Method of Frequency Selection PTT Control Circuit BFO Inhibit Control Crystal Oscillators General Theory of Digital Synthesizer Detailed Synthesizer Operation BFO Reference Oscillators Basic Theory of R T Operation O 10 Detailed Receiver Operation ll Detailed Transmitter Operation 12 Noise Blanker Operation TUNING PROCEDURE General AUDIO PROCESSOR TUNE UP 7H020 Board SMO TUNE UP 7H015 Board R T TUNE UP 7H016 Board TEST POINT AND TUNING ADJUSTMENT LOCATIONS A AUDIO PROCESSOR 7H020 Board B SMO 7H015 Board C R T 7H016 Board SCHEMATIC DIAGRAMS 12D015 SMO Digital Synthesizer 12D016 R T 12B017 FPA 12C018 Interface 12B019 Audio PA 12C020 Audio Processor 26D001 Block Diagram 16C002 Interconnect Diagram Il CPI RECOMMENDED TEST EQUIPMENT LIST 1 OSCILLOSCOPE TEKTRONIX T932 35MHz portable 1200 TEKTRONIX INC P O Box 500 Beaverton Oregon 97077 Reliable good CB 27MHz waveform resolution and triggering 2 RF GENERATOR CLEMENS Model SG 83C 345 CLEMENS MFG CO 630 S Berry Road St Louis MO 63122 314 961 7228 Excellent value solid state generator with calibrated micro volt output and super reliability 3 FREQUENCY COUNTER CPI Model FC 70
15. M rcv mode set 2 0v p p at TP 8 using R314 AM RF generator should be at 1KC 50 modulation AM with a 60dbm 220 UV signal level Check squelch operation at TP 8 Rotation of the front panel squelch control should cause the audio at TP 8 to be cut off Set RF AGC R292 at TP 5 for 1 5 VDC with 50 dbm 700 uv on LSB receive 1KC audio out Check proper RF AGC operation Check R T switching at TP 5 It should be 8 VDC on xmt and O VIC on receive with no rcv signal Set S meter to S 9 with a 50 uv signal generator level on LSB receive with 1KC audio out using R286 SM On the audio processor board peak L501 and L502 for at least l VDC downward deflection at TP 6 with a 50dbm 700UV 23 5 MHz CW RF input to the radio Disconnect the signal generator and connect a wattmeter and 50 ohm dummy load to the radio antenna connector See step 5 of general tuning procedure With a 20 mv p p 1KC audio input at the radio mic connector set R274 RFL for 5v p p audio at TP l on LSB mit Vary audio input level to verify proper ALC operation limiting At a point below 20 mv input the audio level at TP 1 will start to drop above that point the audio should limit at 5v p p Set 90 1KC AM modulation at TP 2 on R T Board with R699 CAR ADJ on SMO board Be sure audio is in AIC limiting when R699 is adjusted Always use an oscillo scope to adjust modulation not a meter Peak L204 L202 L203 L205 and L201 in that order for maximum
16. O v6000 N 1604 e RECEIVE R PROCESSO OUTPUT SMO TX EXCITER R I7MhZNOM E 16 IZOMh z NOM odbm 500 T D IYIDER EMITTER CONTROL J Q 9 Fo w U6OOE AM BUFFER SER i LLO AMP FILTER 12 8Mhz Q u2000 12 803Mhz U600F OSC f AUDIO SW 12 8Mhz RF Sw i osc N RX CLARIFIER Ane mao st N x e CZE ors E E E Jue x Q2 3 RF POWER AMP BUFFER PASS MIXER BUFFER PED ED I POWER 27Mh7 i AMP FIL TER AMP AMP 4 dbm 50a 27Mhz lt I0 2Mhz ow Q a 0207 PASS L202 4 Hai DIO Fit R RF DETECTOR 0193 10 s gt REF ATTENUATOR 27Mhz G 17Mhz odem MME gt lt S FRE 10 2Mhz RF DIQ JFET O 206i SWIT CH PR AM i TX BUFFER Sauren en ERAS Eee Wn D s SIITT jrin A eMe AMP EW Z 021 12 TX BUFFER RF AMP dad LEVEL 0214 N Q216 SPEAKE BLANKER W 5 DELAY 0224 4 AUD 10 SECTION L2N 214 AMP a213 IWRMS o NOISE BLANKER 10 2Mhz NATE U200 4 8 RY SEITE W IF AMP vole P i ACTIVE 0203 4 D205 6 AUDIO i LOW PASS AMP FILTER RF SW SEENEN 00 DRIVER SQUELCH LS IVE GATE a 200 UELCH AUDIO DETECTOR RF FILTER AMP AMP L50I_ O 0510 AMP REC MTR AMP COMMUNICATICNS POWER INC 2407 CHARLESTON RD MOUNTAIN VIEW CA 94043 ume O 9m R306 pare 8 12 77 IFAGC BLCCK DIAGRAM CP40C DRAWING NUMBER MD AR RF AGC l MTR CAL R292 R809 SQUELCH rap PRIMTED ON NO 1000H 10 CLRARPRINT Jior eo 1201 rpa our RXTX 7HOI6 di o c E M 5dbm50
17. by the amplifier The output of U500A drives logarithmic amplifier U500B This amplfier introduces a non linear transfer characteristic and produces compressed full wave audio at its out put The output of U500B drives AGC amplifier U200D which feeds emitter follower Q221 to provide a low impedence audio source to the balanced modulator The output of the balanced modulator 10 200 MHz is fed to diode switch D211 Note that R699 and D614 on the balanced modulator BFO module form the key elements for switched variable carrier insertion during AM transmit operation The output of switch D211 is buffered by Q222 passed by switch D206 and filtered by dual mode filter FL201 see previous sections for details of FL201 operation The output of FL201 passes through switch diode D204 and is buffered by Q205 The output of buffer Q205 is amplified by AGC driver Q207 and detected by D201 and D202 The dc level output of D201 D202 is compared to a fixed 2 volts by U200C The transmit IF signal level is set by R274 before buffer 0222 The out put of U200C drives emitter follower 0209 for a fast attack of C222 and R229 which set the transmit AGC attack and decay time 0209 is an emitter follower ACC driver to the transmit audio AGC amplifier U200D Thus adjustment of the audio gain through U200D adjusts the rf level through the transmit IF chain to prevent over modulation and level the varying audio input levels from the microphone The output of 0205
18. er into the circuitry of U600M 0616 0617 and 0618 The BCD number N is a nine s complement BCD number This is coded as follows Number N N O 0 J O LD P WH m O O O O O O O O O F O OO OO ka E E F OO O O k ka O O iF i O O N a O HOHOHO O H H Note that positive TTL logic levels are used for N Thus O 0 to 0 6 vdc and 1 2 5 to 5 0 vdc 2 PTT Control Circuit Since transmitting on channels 41 to 99 is illegal the transmit push to talk PTT function is inhibited for these channels by the PTT control circuit 3 BFO Inhibit Control Logic gate U600L together with Q604 and Q605 turn off the BFO during AM receive operation 4 Crystal Oscillators All crystal oscillators are of the Colpitts type Some oscillators operate only in certain modes Oscillator ON Modes 12 803 MHz 0614 USB 12 800 MHz Q610 All modes 10 200 MHz Q606 AM LSB 10 197 MHz 0602 USB The front panel clarifier control R814 adjusts the dc bias on D608 12 800 MHz oscillator and on D605 12 803 MHz oscillator to adjust frequency during receive operation only 5 General Theory of Digital Synthesizer The voltage controlled oscillator VCO is a free running oscillator whose freguency can be shifted by changing thedc control voltage applied Increasing control voltage causes higher frequency of operation The output of the VCO is mixed with a fixed crystal oscillator to produce a lower freguency for digital division The output
19. n during AM transmit operation 8 Reference Oscillators A crystal oscillator Q610 operating at 12 800 MHz is used as the primary reference for PLL circuitry Additionally the 12 800 MHz is used as a L O signal to mix with the 16 800 MHz VCO which yields a difference frequency of 4 0 MHz The 4 0 MHz is applied to the programmable divider chain whose output is 5 kHz To maintain a constant 27 MHz output frequency on USB a 12 803 MHz crystal oscillator 0614 is used as the above mentioned L O Furthermore a voltage variable capacitor is incorporated in each oscillator circuit to allow 1500Hz fine tuning of the receiver with the front panel CLARIFIER control R814 During transmit the front panel CLARIFIER control does not function Each side of the control R814 is connected through its respective switchinq transistor 0804 and 0805 In the transmit mode both 0804 and 0805 are turned off which effectively floats the arm of R814 This prevents the user from warping either oscillator during transmit 9 Basic Theory of R T Operation The radio is basically a single conversion superheterodyne type unit with filter type SSB generation Some commonality is used on key components for both transmit and re ceive One key unique feature of the unit bears some explanation for thorough under standing of radio operation A single crystal filter unit is used for all modes of operation AM LSB and USB on both receive and transmit The filter is a dual
20. of the digital divider is compared with a fixed reference freguency A difference in frequency will cause the phase comparator to shift the VCO dc tuning voltage until the VCO is on frequency locked An example will best illustrate this operation If radio operation on 27 00 MHz is desired the synthesizer output must be 16 8 MHz since the radio IF frequency is 10 200 MHz The 16 800 MHz is mixed with the 12 800 MHz fixed frequency to produce a 4 000 MHz freguency out of the synthesizer mixer This 4 000 MHz is applied to the programmable divider and divided by 800 to produce 5 kHz This 5 kHz is compared with 5 kHz produced by dividing the reference oscillator by 2560 Thus synthesizer output freguency is as follows 12 800 MHz N 5 kHz It can be seen that a change of N by one will produce a Ne kHz shift in operating frequency 6 Detailed Synthesizer Operation The VCO Q608 is automatically tuned by varactor D604 and manually set by L603 Its output is low pass filtered by C615 L604 C616 and applied to output buffer 0609 and loop buffer Q612 The output of Q612 is applied to loop mixer Q611 The other input to 0611 is the output of the 12 803 MHz 0614 oscillator for USB During USB operation the output of the 12 800 MHz oscillator 0610 is kept from the loop mixer by switch U600F For LSB and AM 0614 is turned off and U600F switches 0610 output into the loop mixer Both oscillator outputs are low pass filtered by C641
21. or 8VDC at TP 8 Set xtal oscillators on frequency Be sure to use a high impedance probe with frequency counter a XL 1 12 802850 MHz at TP 6 USB xmt with C640 b XL 2 12 800 MHz at TP 6 LSB xmt with C648 c XL 3 10 197150 MHz at TP 7 USB with C667 d XL 4 10 200 MHz at TP 7 LSB with C652 Check for no signal on AM RCV at TP 7 with an oscilloscope On channel Ol adjust L603 for 2 4 VDC at TP 3 CP 400 R T TUNE UP 7H016 Board Ls 2 10 11 12 13 14 15 16 17 18 All receive tuning is done with a signal generator connected to the radio antenna connector On channel 20 peak L206 and L207 at TP 4 for maximum 16 8 MHz voltage At least 8v p p should be present On channel 20 tune 1208 L209 L214 L211 L212 and L213 on LSB for peak S meter reading Adjust generator frequency to keep audio out put at 1KC Use R286 SM to keep the S meter at S 9 and R306 IF AGC to keep the 1 KC audio on TP 8 at 3 0v p p Be sure audio is unsguelched Keep reducing the rf generator input level as the receiver is tuned to just barely keep the level in full AGC Full AGC is usually at signal levels above 10 UV Check clarifier operation by its rotation causing a change in receive audio frequency For 60dbm 220 UV signal level set 3 0 p p at TP8 with R306 IF AGC Check USB receive and clarifier operation for proper sensitivity and operation Do not retune the receiver on USB In the A
22. y zo RS29 L 72v0C MPS HIO lt l IVDC K C518 T C519 1000 MPS HIO RS30 270 o Qsit TI 0508 G AUDIO AMP DC VOLTAGES 1 13 6 4 13 4 5 72 6 1 27 7 6 95 8 00 av IO b 12 6 7 4 vr 7voce w 2 PA SAMPLE IOK A412 eet MR750 040 amp COMMUNICATIONS POWER INC 2407 CHARLESTON Rd MOUNTAIN VIEW CA 94043 para 8 MAR 77 AUDIO AMP CP 400 TP3 Vpp Q serge TPS O Svpp 1000 R522 1000 220K K RSI8 R519 R523 M60810 220K 22K R520 Saz Ol Frid NB OUT c520 c32 TO Rr 330 6322 RSIS Ol Lire MOvoc 2200 R556 4 COMMMECATIONS POWER INC 2407 CHARLESTON Rd MOUNTAIN VIEW CA 94045 0 AUDIO PROCESSOR CP 400 PIN 7HOZO 1200 6 5 COMMUNICATIONS POWER INC 2407 Charleston Road Mountain View CA 94043 415 965 2623

CP400 SERVICE MANUAL COMMUNICATIONS POWER, INC.

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