CPI 2000 - CB Gazette
Contents
1. 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 35 FREQUENCY COUNTER CPI Model FC 70 170 4 AUDIO GENERATOR HEATH MODEL IG 18 approx 100 CP2000 BASE DETAILED CIRCUIT DESCRIPTION Ts Method of Frequency Selection The front panel switch SW 1001 provides the binary coded decimal BCD outputs corresponding to each digit of the channel number selected Data from the channel switch also drives the LED displays IC s U900A and U900D convert the BCD information into the format required to drive the seven segment displays LED s U900B and C BCD coding is as follows for each decimal number Number C8 CA C2 CI 0 0 0 0 0 1 0 0 0 1 2 0 0 aD 0 3 0 0 1 1 4 0 1 0 0 5 0 0 1 6 0 1 1 0 7 0 1 1 1 8 0 0 0 9 0 0 1 C1 C2 etc correspond to the 1 s 2 s etc place in the binary equivalent of each digit of the channel number Note that each decimal digit is binary coded not the entire number C l C2 Col C22 etc are the bits Of C the second digit of the channel number See example on following page Channel 23 is 2 3 o j a P ME ue Qo N CO Q C CIC C18 C44 C42 Cy WHERE C 23 WER and C 3 Also note that TTL negative log2. Full AGC is usually at signal levels above 10 UV For 60dbm signal level set 3 0v p p at TP 8 with R306 IF AGC Rotate clarifier control and verify its operation by noting a change in receive audio frequency 12 Check USB receive and clarifier operation for proper sensitivity and operation Do not retune the receiver on USB 13 In the AM rcv mode set 2 v p p at TP 8 using R314 AM RF generator should be at 1KC 50 modulation AM with a 60dbm 220 UV signal level 14 Check squelch operation at TP 8 Rotation of the front panel squelch control should cause the audio at TP 8 to be cut off 15 Apply a 50dbm 700uv signal Rotate R292 RF AGC from CCW position to CW while observing front panel S meter A 1 16 or more deflection of the pointer indicates proper operation of the RF attenuator circuits Set RF AGC R292 at TP 5 for 1 5 vdc with 50 dbm on LSB receive with 1 KHz audio out 16 Check R T switching at TP 5 It should be 8 VDC on xmt and 0 VDC on receive with no rcv signal 17 Set S meter to S 9 with a 50 uv 73dbm signal generator level on LSB receive with 1 KC audio out using R286 SM F Noise Blanker Bd Alignment 7HO44 1 Connect a rf signal generator to the radio antenna connector Set to 23 5 MHz at a level of 50dbm 700uv with no modulation 2 Tune 1401 and L402 for at least 1 VDC downward deflection at TP 1 3 Plac
3. L205 on Ch 40 Check power balance Re check 4 watt level and adjust R205 if required 6 Turn to LSB mode and check power level with limiting 1 KHz modulation It should be at least 10W s Set front panel meter to read 4w with no modulation on AM Ch 20 using TX MTR CAL pot R557 located on the Interface Board 7HO43 There is a small hole through the circuit board to allow adjustment from the back side 8 Remove audio generator and using a microphone check the whistle and speech modulation waveforms on AM LSB and USB Be sure AM carrier level is 4w and adjust R699 CAR ADJ for 90 whistle modulation 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 95 Return to Section C Interface Board 7HO43 Adjustment RECEIVER 10 Connect a signal generator to the radio antenna connector Be sure to remove microphone or transmit keying circuits to avoid possible damage to generator LI On channel 20 tune L208 L209 L214 L211 L212 and L213 on LSB for peak S meter reading Adjust generator frequency to keep audio output at 1KC Use R286 SM to keep the S meter at S 9 and R306 IF AGC to keep the 1KC audio on TP 8 at 3 0v p p Be sure audio is unsquelched Keep reducing the rf generator input level as the receiver is tuned to just barely keep the level in full AGC
4. L210 C255 resonate at 27 MHz on the output of Q223 This output is fed into the gate of JFET mixer Q201 The source of Q201 is fed with local oscillator signal by Q206 The 10 200 MHz IF output of Q201 is fed through a delay network consisting of L211 L214 C296 C297 and C258 The delay network is required to insure proper operation of the noise blanker Output from the delay circuit goes to the crystal filter P 201 via diode switch D203 and D204 For SSB operation 10 vdc 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 amplified by U200A and U200B about 80db of IF gain For SSB operation the output of U200B is switched by D211 into the product detector into the product detector BFO Q214 is the AMand AGC detector Q216 is connected as a temperature tracking diode to bias Q214 The output of Q214 is low pass filtered by R301 C288 to provide audio and a DC voltage for AGC operation This DC component is applied to comparator U200E R306 sets the comparison voltage for U200E The output of U200E drives follower Q212 to provide fast attack of C277 R297 and R298 set the AGC decay In the AM mode R298 is shorted by Q217 which shortens the decay characteristics of the AGC R283 and R281 apply AGCto the IF amplifiers U200C compares the IFAGC level set by R292 to begin rf AGC R298 and D20
5. 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 receive One key unique feature of the unit bears some explanation for thorough understanding 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 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 sideband If the BFO has been shifted down 3 KHz for USB it is necessary to shift the SMO LO input up 3 KHz to maintain a constantchannel frequency This is why two oscillators 12 800 MHz and 12803 MHz are used in the synthesized master oscillator SMO 94 Detailed Receiver Operation C117 C123 and L105 L108 constitute a low pass filter at the rf input connector which is shared with the receiver and transmitter From the low pass filter the receive rf input is coupled by C116 to D105 D105 is a PIN type diode which acts as a shunt attenuator for manual and automatic rf gain control on receive and as a shunt shorting switch for transmit operation C250 C251 C252 and L209 provide the required impedance transformation for the grounded gate preamp 0223
6. external 13 6 volt source power is applied to the input of the 5 and 10 regulators Also the external DC is applied directly to the audio PA and the RF PA module D802 D803 and D804 route the external DC to the proper points in the regulator circuitry CP2000 BASE TUNING PROCEDURE A General 1 Tune the radio in the sequence given It is imperative that the power supplies be adjusted to their correct output voltage before attempting any alignment 2 A Second Class or higher FCC Radio Telephone License is required to make any frequency or transmit adjustments to the CP2000B 3 All receive RF inputs from the generator are applied to the radio s antenna connector 4 All transmit measurements are made with a 50 ohm load connected to the radio s antenna connector through a good quality wattmeter 5 Microphone connections Pin 1 Audio hot Pin 2 Audio ground shield Pin 3 PTT Hot Pin 4 PTT Return 3 and 4 are shorted together for transmit 6 Block Diagram of Test Setup Antenna CP2000B 120VAC Radio gt Wattmeter gt 50 N Load Microphone i Low d min l rating Signal ken Generator Audio Generator Oscilloscope for Mod Measurements B Power Supply Adjustment Assy 7HO46 1 Connect radio to a suitable 120 VAC source Be sure that the D C power cable is not plugged
7. frequency during receive operation only 4 General Theory of Digital Synthesizer The voltage controlled oscillator VCO is a free running oscillator whose frequency can be shifted by changing the DC 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 frequency for digital division The output of the digital divider is compared with a fixed reference frequency 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 frequency 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 frequency is as follows fou 12 800 MHz N 5 KHz It can be seen that a change of N by one will produce a 5 KHz shift in operating frequency 5 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 Q60
8. rozar s q 1 j Sgr El Pr 2 M magne a gt Ut 07D oe Vie Kai DB E 1 ETE an dev han un 42123433 NIE any wap M 3 pe WOlYMWUWDO SIY 130 37v Sim Xl rg soe one VIHB SSvd Garg MdgH JN 1 MERO A H 4 a m m EE T t Teen m U U C UU 4 e re w eos i 1 254 _ CT _____ a m x set Bw 304 Fi dg 292 M31SVW UM m Lo tet 250 ATdS HMd 7 03Z1IS3HINAS Dun JERII Un ODA Kg na t cec r TN j 1 1 1 ms nny ur W3LTIS ud t teve MOT f I H ERRE guy we ny r 4 Y34308 D Boose 00077 mv I tngh 033 me 4313078 dog MITA i d Ca Dei h 7 QM t wos mgg d NY Lane 907 OVINOS 307703 L MON Zumi A IREZ E Lalo amy 2908 184100 ORS W D b BUE yis Mb PEREIS or 950 5v4 MO 310vyn YOON a I Zur OLEUO 1 s n00v3w DNFANIO SUD SANT MWJiMS 1 4w3m235 M3dO230 VINO OF 1 Mm men I BOOS BAD am D 31 BOL Y TICO e NT 31 73 ev i I ffys NO 83 208 032wvvg i LELE I aso O5 KEN Nj VEN FONOS way es ar 82123132 I fem oa al ov dr i 360 334408 358YHd l 9bOHZ NE E B OO02d9 18 AMIANS YMd iron toro 2gAS B SOE wera Ira DP WO4 MADHI SIEWITOA ONO FIFFI saionza f 02 78 6082 zogr Ki bi UI BOKWY i Me Olai Oht gt A62 2 0028 rost sm TOR dk DIONE A ODO oer DIES O Woo m Prex rom T3HOHa Oy 36 P ose Som 92 res v
9. 8 assure full receive rf AGCshutdown during transmit 0208 is the PIN diode D105 driver AM recovered in detector Q214 passes through automatic noise limiter diode D214 and associated circuitry before reaching Q219 The ANL can be turned on and off with front panel switch SW502 Q219 is a FET switch which selects either AMor SSB audio for amplifier U200F R314 is to balance AM SSBaudio levels into U200F The output of U200F goes through squelch gate Q215 to the output amplifier U200E senses a DC IF AGC level set by the front panel squelch control R809 to open the audio squelch gate Q215 U800C and associated circuitry amplifier the audio from U200F to a sufficient level for driving a 4 ohm speaker 10 Detailed Noise Blanker Operation A TRF Tuned RF receiver operating at 23 5 MHz samples the output of the low pass filter located at the antenna input to the transceiver This TRF receiver consists of rf amplifiers Q 401 and Q403 followed by a noise pulse detector Q405 and Q402 The output of the pulse detector drives a one shot Q404 which drives a shunt rf switch Q224 During the period of time an interfering noise pulse is present the switching transistor Q224 prevents the signal from passing through the receiver s 1 f amplifiers As a result objectionable noise pulses are removed from the receiver s audio output 11 Detailed Transmitter Operation Microphone audio is amplified by Q501 and is
10. 9 and loop buffer Q612 The output of Q612 is applied to loop mixer Q617 The other input to Q611 is the output of the 12 803 MHz Q614 oscillator for USB During USB operation the output of the 12 800 MHz oscillator Q610 is kept from the loop mixer by switch U600F For LSB and AM 0614 is turned off and U600F switches Q610 output into the loop mixer Both oscillator outputs are low pass filtered by C641 L606 C642 Q611 output is low pass filtered by C623 L605 C624 and converted to TTL level pulses by Q615 Q615 output is applied to the programmable divider which consists of U600G N3 U600H ND and U600J N1 The programmable divider output is applied to the phase comparator UCLA and U600B which compares the pulses with the 5 KHz output of the reference divid ers U600E 16 U600D 16 and U600C 10 The output of the phase comparator is level shifted to 10 volt pulses by Q613 Note that the phase comparator 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 output is at O or 1 logic levels and does not have a pulse output the loop is not phase locked The pulse output of Q613 is filtered by C603 607 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 6 BFO Two crystal oscillators are u
11. CP2000 BASE STATION SERVICE MANUAL COMMUNICATIONS POWER INC PDF MANUAL FROM http www cbgazette com TABLE OF CONTENTS I RECOMMENDED TEST EQUIPMENT LIST H DETAILED CIRCUIT DESCRIPTION Method of Frequency Selection BFO Inhibit Control Crystal Oscillators General Theory of Digital Synthesizer Detailed Synthesizer Operation BFO Reference Oscillators Basic Theory of R T Operation Detailed Receiver Operation DO ON ON AE 10 Noise Blanker Operation 11 Detailed Transmitter Operation 12 Detailed Power Supply Operation HI TUNING PROCEDURE General Power Supply Adjustment 7HO46 Interface Board Adjustment 7HO43 SMO Board Alignment 7HO42 RXTX Board Alignment 7HO16 Noise Blanker Board Alignment 7HO44 m m Ow gt TEST POINT AND TUNING ADJUSTMENT LOCATIONS A Power Supply 7HO46 Board B Interface 7HO43 Board C SMO PH042 Board D RX TX 7HO16 Board E Noise Blanker 7HO44 Board lt SCHEMATIC DIAGRAMS lt 26CO02 Block Diagram 12C046 Power Supply 12C043 Interface 12DO14SMO 12BO47 Switch Display 12DO16R T 12BO45 RF PA 12BO44 Noise Blanker RECOMMENDED TEST EQUIPMENT LIST gmammuns 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
12. P 7 LSB with C652 4 Check for no signal on AM RCV at TP 7 with an oscilloscope 5 0n channel 1 adjust L603 for 2 4 VDC at TP 3 td RX TX Bd Alignment 7HO16 Transmitter 1 Connect a wattmeter and 50 Ohm dummy load to the radio s antenna connector See step 6 of General tuning procedure section 2 0n channel 20 peak L206 and L207 for maximum 16 8 MHz voltage at TP 4 At least 8v p p should be present 3 With a 20mv p p 1 KHz audio input at the radio mic connector MIC GAIN full CW and COMP IN on LSB transmit set R274 RFL for 0 5v p p audio at TP 1 Vary the audio input level 20db above and below the 20mv level to verify proper ALC operation At a point below the 20mv level the audio at TP 1 will start to drop and above that the audio should limit at 0 6v p p 4 Remove one end of the cable which goes between the RX TX and SMO board that is labeled SMO Set 90 1 KHz AM at TP 2 on RT board with R699 CAR ADJ on SMO board Be sure audio is in ALC limiting when R699 is adjusted Always use an oscilloscope to adjust the modulation not a meter Re connect the SMO cable Je Peak L204 L202 1203 L205 and L201 in that order for maximum power output on CH 20 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 1204 for maximum power on Ch 1 and
13. e the radio in LSB receive and modulate the generator 23 5 MHz at 1 KHz 50 AM If the blanker is operating properly a 1 KHz tone will be heard on the receiver PWA SUPPLY FH d BRO COMPONENT SIDE 2333 CS SA B 25809 tov TP O reve SVTP CURRENT FOLGEA K AD 12 6Y re INTERFACE HO43 BRD REAR VIEW SHO 7HO42 ERD COMPONENT SIDE 2225232 ng manam l e ilta 78 EN J po onen 20070 s y PHO i tns d 27 L Sov MAT NY u FAN PILIS airs wa73nbs5 l H2330D 1343705 i BaQen 30229 LOA e J Ni 7 L a 1 EFE i P TD m Bc lt 7d WW Dore 1 1 WW 9020 mica Priora h e H D 1 er m Mg Pn TIR wu nns re 209 y MS Ab a IN LIT ay 1 aes l ZAR FOL vz2D as wand bw qn n 8 27 A39uv ie MA Ae Ne d olla FOTO S 2214 22 22 zrazal ec AJ 2220 x RT Um mes k 222b 4 rose 206 n v2 a rav 27v Thant xi LERENI Ei Ul onsen me ig m _ f EA i AW NASA wn s nn gor rd a ra oa 304 ha H3112X3 X1 mar a P t so Po D C ind d H3 323M 1 ae p ol _ rind e NI d y 4208 aay DT EE DE on 1 ar 1 Fame wid d j foe I i De vC y m
14. followed by U500A which is a high gain low distortion amplifier When overdriven the output of U500A symetrically limits the audio level applied to the compressor which prevents overmodulation C507 and C512 determine the amount of audio pre emphasis introduced by the amplifiers The audio after amplification and pre emphasis is applied to U500B which is connected as a logarithmic amplifier This amplifier introduces a non linear transfer characteristic and produces compressed audio at its output A front panel switch SW 504 selects between normal and compressed audio for transmitter modulation The output of U500B drives AGC amplifier U200D which feeds emitter follower Q221 to provide a low impedance 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 in the balanced modulator 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 dri 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 Q222 The output of U200C drives emitter fo
15. ic is used for the channel switches 0 2 5 to 5 vdc and 1 0 to 0 6 vdc The radio operating frequency is determined as follows fo 27 405 MHz N 5 KHz 12 800 MHz 10 2 MH where fo operating frequency N synthesizer divide ration E N N gt N3 N is a three digit BCD number N N2N3 determined by feeding the channel switch outputs into U600N for N and N3 and N control circuit for Ni U600N requires negative voltage for proper operation This is done by feeding a 50 KHz pulse from the synthesizer into the circuitry of U600M Q616 Q617 and Q618 The BCD number N is a nine s complement BCD number This is coded as follows Number N8 N4 N2 N1 0 1 0 0 1 1 1 0 0 0 2 0 1 1 1 3 0 1 0 4 0 1 0 1 5 0 1 0 0 6 0 0 1 7 0 0 T 0 8 0 0 0 1 9 0 0 0 0 Note that Positive TTL logic levels are used for N Thus 0 0 to 0 6 vdc and 1 2 5 to 5 0 vdc 2 BFO Inhibit Control Logic gate U600M together with Q604 and Q605 turn off the BFO during AM receive Operation 35 Crystal Oscillators All crystal oscillators are of the Colpitts type Some oscillators operate only in certain modes See following page Oscillator On Modes 12 803 MHz Q614 USB 12 800 MHz Q610 All modes 10 200 MHz Q606 AM LSB 10 197 MHz Q602 USB The front panel clarifier control R508 adjusts the DC bias on D608 12 800 MHz oscillator and on D605 12 803 MHz oscillator to adjust
16. in also 2 Apply power to the unit with front panel OFF ON switch The lights behind the meters should be lit 3 Connect a voltmeter between C 811 end and the chassis Adjust R835 for a reading of 13 6 volts 1 4 Connect a voltmeter between C809 end and the chassis Adjust R808 for a reading of 10 0 volts 1 5 Connect a voltmeter between C806 end and the chassis A reading of 5 volts 3 should be noted No adjustment is possible in this circuit 6 Ripple on the three supplies should be less than 10mv p p Measure across C811 C809 and C806 for corresponding 13 6 10 and 5 volt supplies 7 To check DC operation remove the AC power source and connect the radio to a 5 amp or greater source of 13 6 volts 5v with the DC cable provided Measure the voltage in steps 4 and 5 above They should be the same as noted on AC Step 3 voltage will be equal to input supply voltage C Interface Board 7HO43 Adjustment 1 This board contains control metering and audio processing circuitry 2 Connect an audio oscillator to the microphone input connector at 20mv p p 1KHz Measure the voltage at TP 1 which should be 42v p p 3 Turn MIC GAIN control full clockwise and measure 3 2v p p at TP 2 4 Move scope to TP 3 and observe 1 0v p p of compressed audio 5 With the scope at TP 4 the level should be 0 5v p p with the front panel swi
17. llower Q209 for a fast attack of C222 and R229 which set the transmit AGC attack and decay time Q209 is an emitter follower AGC 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 overmodulation and level the varying audio input levels from the microphone The output of Q205 also is passed through buffer Q203 to the gate of the transmit rf mixer JFET Q204 The source of Q204 gets LO injection 16 8 MHz from amplifier Q206 The output of Q204 27 MHz is bandpass filtered by C205 209 and L202 L204 A broad band amplifier consisting of buffer Q225 and push pull amplifiers Q226 and Q227 follows the three section transmit filter Class A biasing is employed on all three devices to insure very linear operation Interstage transformer T502 and output T501 provide optimum impedance transformation to following stages An output filter L201 L205 and associated capacitors removes all out of band spurious energy This filtered drive signal is applied to R205 which sets the rf drive level to the linear transmit power amplifier assembly The transmit power amplifiers Q101 and Q102 are operated Class AB with transformer interstage matching Q102 the final rf amplifier is operated Class B with quiescent DC bias set by R107 R108 and temperature tracking diode D104 Q102 also uses transformer type input and output matching The output of Q102 passes thro
18. r me ver 99T or 4x3 FILI fone ones oat ANT A YE EB DO 5kHdTOS I oer 282 oc war N UE Her 30459 vor shiy re im E 2192 nen 0 OG lt lt T D KG Y M S Lei se FX BAND PASBFRIER St ALC DETECTOR COMPARATOR PEAK DETECTOR re du ZS ec opt Je ears Quer nii TRS i O geg feo xa mr TA RE BUFFER oie LS TX RF BUFFER oe q Fi all Elim cde MIXER eos voc c I ED AX MIX een wre CB T edid s 24 uo lt Cay eros er Nal ES Bro gr Eure aro i EFE Wi aro EU A Adast Char Faso 3 Ts Gef wevac 5 Sae 1 o e MEDIAM ily reg ER ams Nal AM Ten er Vua FwEIC AMP tts Zi amp DETECTOR ana D AX RF ANP H He ad er 28 SES v ege G cnr W 1377 vA Age A ar bm E E ero 100 spe Ara opt je j 1 F M error rr ve wos O Er em RF AGC AMP sar E Arte 2 sand us Ortovec C I Ka e ZER cin gt a Y PEAK DETECTOR aer A 45 1000 ator Save are E che m auDio a sautes S A Y gos Marsi 7 D STD TEST CONDITIONS S IS CH IE 17 AN MAL Au ODE e poda FF A VEL TIRE Ca 2h BFA an puha A OPE AF AMP 4305 Aus SQUELCH C At ar Gare zm SC z ansasi s T oir src GO CE cre lt NM F SELOY NOSE Se ioe C SVOC w sie um ansa A LEVEL HE aS os 10x 30 voc D ara E 9 voc Ap Pk Oriowoc dia dE cate I were 1000 FIOR ar A lt A y or wars ra
19. sed for the BFO The 10 200 MHz Q606 is used for AM and LSB The 10 197 MHz oscillator Q202 is used for USB only Both oscillator outputs are low pass filtered by C664 L607 C667 and amplified by Q607 The output of Q607 is fed to the double balanced mixer D610 D613 which is the product detector for SSB receive operation and the balanced modulator for AM and SSB operation R699 and D614 form a network for carrier reinsertion during AM transmit operation 7 Reference Oscillators A crystal oscillator Q610 operating at 12 800 MHz is used as the primary reference for the 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 Q614 is used as the above mentioned L O Furthermore a voltage variable capacitor is incorporated in each oscillator circuit to allow 800 Hz fine tuning of the receiver with the front panel CLARIFIER control R508 During transmit the front panel CLARIFIER control does not function Each side of the control R508 is connected through its respective switching transistor Q505 and Q506 In the transmit mode both Q505 and Q506 are turned off which effectively floats the arm of R508 This prevents the user from warping either oscillator during transmit 8 Basic Theory of
20. tch set to the COMP IN position and 57v p p in the OUT position 6 Connect pins 3 and 4 of the microphone connector together This places the radio in the transmit mode The front panel LED should be lit 7 With the radio in transmit check the voltage at the collector of 0509 which should be 9 9 volts Pin 8 on 7HO16 comb 8 After completion of the above procedures go to Section D SMO Bd 7HO42 alignment procedures The remaining steps in this section are completed after alignment of 7HO16 9 Using an external wattmeter of known accuracy set the front panel meter to read the same power 4 watts typical with no modulation on AM Ch 20 using TX MTR CAL pot R557 located on the Interface Board 7HO43 There is a small hole through the circuit board to allow adjustment from the back side 10 Check for proper operation of the VSWR meter circuitry Place front panel switch to VSWR CAL turn control for full scale deflection on front panel meter CAL Switch to VSWR READ should be 1 5 or less for most good loads D SMO Bd Alignment 7HO42 1 Set R699 at rotation CAR ADJ 2 CHECK for 8VDC across C643 3 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 T
21. ugh a 9 section low pass filter which insures complete removal of undesired harmonic energy Between the output of the filter and antenna terminal T104 and T105 are connected in a directional coupler configuration The resulting output is detected by diodes D101 and D102 to give forward and reflected power information A front panel switch SW 505 selects between the two DC voltages FWD and refl before application to VSWR meter amplifier USOOC A sample of the forward power DC voltage is used to drive the rf power output meter and associated drive circuitry 12 Detailed Power Supply Operation The power supply circuits provide the operating power for the various modules in the transceiver Electronic regulation is used to provide stable low ripple output voltages of 5 10 and 13 6 VDC AC power is applied to the primary of T801 through line fuse F801 and POWER switch SW 801A The secondary AC voltage of T801 is applied to the bridge rectifier assembly D805 and filter capacitors C803 C804 which provides full wave rectified DC for the series regulators Both the 10 and 13 6V regulators operate in the same manner A precision regulator U800A drives a series pass transistor QBO3 for 10V and correspondingly U800B drives Q804 and Q805 for 13 6V output Q801 and Q802 serve as over current shut back switches for the protection of the regulators The 5V regulator U800D derives its input voltage from the center tap of T801 For DC operation from an
22. wes Site 27 pe ores ane AM AN m e MS se cr zo on 4340 Ris FACTOR Bauch RX TX CP 400 CP 2000 MEVIGION P Pann Gro FEE m 100
Download Pdf Manuals
Related Search