SA501andR527 areinstalled inthe inputpart of HF antenna terminalasthecountermeasure against the thunder.Theelectric chargeof HFantenna isdischarged at R527, and whenthe voltage
becomesoverabout 300V, the gap of SA501isdischargedsothatthe receiving inputcircuitisprotected.The inputsignal fromHF antennaispassed throughthe transmission/reception selecting relayRL513. The followings are preventedinLPFconsisting of 1525,L526,C580, C581and C582:2mbandimagereceiving,passing throughthe First
IF(71,75MHz)andleaking ofthe firstlocaloscillating frequency (72~130MHz) to
theantenna terminal.
b. 50MHzAntennaInput
2)MainUnit
a.FrontEnd
Thereceiving signal fromthe antenna of50MHz band ispassedthrough theLPFfortransmission/reception and passedthroughthe transmittingpowerdetection circuit,thenled totransmission/reception switching circuitconsisting of D508 and
throughtheattenuator circuit(ON/OFF) of about 20dB consisting of RL515,R528andR531the signal isled tothe Mainunit.
Thereceiving signal output fromFilterUnitisfedtoMainunitthroughCN2. •
HPF, consisting of L19, L20,C47, C48,C49, C50, C51andC52, eliminates thestrong radiosignal ofMW band of 1.6MHzor below. Incaseof receiving thesignal of1.6MHzor below,the sensitivityiscontrolled bythe attenuator inR37andBPF1,also the signal isseparatedinto1.6MHz, overor below.5 BPF unitsconsists of 9filters.Each filtercoversthe following frequency range.The frequency of 2.5MHz or more consists of ChebyshevBPF,andunder 2.5MHz frequency band isLPF. TwoBPF'sare installed onthe sameunit.Nottobeinfluencedsomuch,the distant frequency band BPF’sarecombined.
1.6MHzBPF1
-
1.G-
2..5MH2
2.5 -4.5MHzBPF33.5MHz
4.5 -7.5 MHz
7.5-10.5MHz
14.5MHz
10.5-
14.5-21.5MHzBPF318,21MHz
21.5-30MHz50 -54MHz
BPF2
BPF4BPF110MHzBPF214MHz
BPF4
BPF5
1.8MHz
7MHz
24,2BMHz50MHz
PassingthroughBPF, the signal turnsON/OFF inthe switching diode, D29andD30.Thispreamplifier isthe parallel groundedgateoperationofQ9 and Q10(2SK2171), sothe unitcan obtaina goodperformanceat ahigh level inputsignal withlowNF.Thewiderangefrequency fromabout 1MHzto60MHzisamplified about 10dB.This lOdBpreamplifierand20dB attenuator inthe Filterunitare combined,then bypressing RF gainswitchonthe frontpanel, oneof foursteps, -20,-10, 0,or +10dB isselected.
TheLPF, consistingof L52, L53, L54,C103, C104,C105,andC106, preventsthe followingfirstreceiving mixerfrom thelocal oscillation leaking, and alsopreventsthe firstIFandimage of the spuriousreceiving.Thefirstreceiving mixerconsisting ofQ10and Q11isthe balancedmixer,inwhichthe local oscillatingsignal isfedtothegateof2SK2171.7he 3rdinterceptpointisabout 20dBm, andlocal oscillator of about 2VP-Pisfedtothe gate.Thereceiving signal isconvertedintothefirst IFof71.75MHz.Asthe ratioof the spuriousinterference isdecreasedin50MHzbandmode,the trapof 71.75MHz consisting ofL72 andC107keeps the ratioofspuriousinterfer
ence70dB or more inallband.
b.TheFirst IFAmplifierCircuit
c. TheSecondMixerCircuit, TheSecondAmplifierCircuit
d.IFFilter
FL1: A and FL1:Bare the crystal filtersof 71.75MHz. By the combination of twofilters,the unithasthe characteristics of the band widthof15kHz ormore/3dBandthe value of guaranteedattenuation of 70dB ormore. Herethe imageratioisdetermined 70dB ormore (approx.80dB}. ThefirstIFamplifiercircuitof Q12 islocatedbetweenthecrystal filterstopreventthe loss inthe front-end and mutual
interference.
Thefirst IFamplifiercircuitQ12decidesthe sensitivityafterpassing the mixer.
Thereceiving signal(71.75MHz)andthe secondlocaloscillating frequency
(71,295MHz) ismixed,andunwanted signal iseliminated inLPFconsistingof L17,L73andC36, thenthesignal of 455kHz isgenerated. After passing through theswitching diodeD8,the signal isamplifiedinQ22. Thesourceof Q22 iscontrolled by theoutput ofthenoiseblanker circuit.
After passing throughthe transmission/reception switching diodeD9,the signal isled tooneoi threeceramic filters of455kHz. Theselectivity isdecidedhere
Each filterhas4switchingdiodes(D3-D48) infront andrear to isolate the filter.
The isolation isrequiredthe value ofguaranteedattenuation of eachfilter(approx. 70dB) or more. Thediodeconnected inparallelinfrontandrear of noused filterisshortand the diodeconnectedinseries isopen. Thecombination of openandshortisusedtogetthe highisolation.Themodes, transmission/reception andwide/narrowof thisfilterareselectedby
Q36-Q46,D79,D80, D82,D83,D84.
e.TheSecondIFAmplifierCircuit
f. DemodulationCircuit
g.CWAudioFilter
Afterpassing through thefilter,the signal isled tothe transmission/reception switchingdiodeD49,andamplifiedinQ23and Q24, thenbuffered inQ25.TheAGCvoltageisapplied tothe secondgateof Q22, Q23andQ24.
The output level of 025isfixed becausethe AGCvoltageisaddedtothereceivingsignal.Thisoutput signal isused for the demodulation inSSB, AMandCWmodesandAGCdetection.
Inthe FMmode, after passing throughthe transmission/receptionswitching diode ofD49,a part ofreceiving signal isfedto1C7(MC3357) from C221,thenitisIF-amplifiedand demodulated.C214isconnectedinparallel tothe feedbackresister R182,and the resister isde-emphasized. Eveninthe FMmode,Q23, Q24 andQ25 areactive,alsoAGCis operated.
InSSBand CWmodes, the following local oscillating frequency issuppliedfrom
PLL unittoIC3balancedmixer, thenthe signal isdemodulated.
The receiving signal isfedto Pint,and local oscillationPin3, then picked upthe
demodulation output of approximately 100mV from Pin7.
USB456.5kHz
LSB453.5kHzCWU455.8kHzCWL454.2kHz
The outputisledtothe switching circuitof eachmode, andtothe CWaudio filter.
InAMmode, the signal isdetectedinD51,thenledtoIC5.InFMmode, the signal isdemodulated andde-emphasizedinabove-mentioned IC7,thenled toIC5.
IC4isthe active filter,which consists of the combination of low-pass filterand high-
pass filterinthe operational amplifier. Ithasthe band widthof about 600Hz(-6dB)
centering the trequencyof about 800Hz.
SHIFT
+IF
SHIFT
+IF+1FSHIFT
SHIFT
+IF
h.AF,AGCTimeConstantSelection
GO
1C5isthe analoguemultiplexerwhich has 2 circuitswith4 contactpoints,andswitches the demodulation outputineverymodeandAGCtime constant. ThevoltagecombinedinD55andD56isinputto Pin9andPinl 0,then the outputof
1C3(SSB, CW-W),the modulationoutput of FM/AMandCWaudiofilteroutput(CW-N) areselected. Thevoltageof 8V isapplied toPin6 (INHIBIT) when transmitting,andthe modulation outputisturnedOFFunconditionally.
IC13 isthe dual electronic volume controlled by thevoltage.Thevolume iscontrolled bythe AFGAINVRonthe front panel. Pin5 isthe controlterminal. Thevalue of the attenuation isthe minimumwhen the control voltageisabout 3.4V,andthe value is90dBor more at maximumwhen the controlvoltageisabout 3.1V.
Oneof thecircuitsisfor volume control of the demodulation sound, and theother
for the volume control of thebeepand sidetone.The beepandsidetonecan be
heard evenifthevolume issettothe minimumpointandsoundtone isrelated withAFGAINVR.Thesquelch circuit(IC14:A, Q14)controls Pin5. The outputofIC14: Aactivates toclosethesquelch whentransmitting,soQ14isturnedOFFinD85to control thevolume ofthesidetone.Thereceivingsound isfedtoPin6andappliedfromPin7. Asfor thebeepand
side tones, Pin2isfor inputandPin1foroutput.Thesetwooutputsarecombined withthe inpulof LPFamplifier IC12:A. ThehightonenoisethatisgeneratedinIFamplifier isdecreasedbyLPFamplifier.Theoutputof IC12:AisattenuatedinR309 andR310togetthe samelevel withIC20, andalso todecreasethe noise. IC20 isthe AF power ampliiier whichcangetthe outputof 2Wor more(THD 10%) at 8£2load.TheripplefilterconsistsofQ51andC260.
TheAGCvoltage issupplied onestageto firstIFamplifierand three stagestosecondIFamplifier. TheseIFamplifiersconsistof 3SK131. AGCvoltageisappliedtothe Gate2. TheIFamplifiersaredesignedthatthe gain ischangedlinearlycorrespondingto the AGCvoltage.
D53 andD54are the rectifier,andQ26isDCamplifier. D50,the anodeissettoabout 2V inR176,D110,D111andR177. Usually AGCvoltageisapplied2.4V.
the AGCvoltage.WhenAGC-FASTisselectedinSSB/CWmode, C205andC206areconnected between5V andAGClineinparallel.Theattack timeofAGCisdeterminedinR167andC206, then the releasetime isdeterminedinR168 andC206. The characteristics are "fastattack" and"slow release". IncaseofAGC-SLOW,the analogueswitchIC6 isturnedON,then R175andC287are connectedinparallel.ThereleasetimeislengthenedbecauseofC287. Incaseof AM,C206iscon
nectedinparallel,then the attacktime is delayed, which isthe averagetype. D110andD111isthe thermal compensationof D50.inreceiving AM, AGCisthe averagetype not tofollow the modulation.
I.SMeter, Squelch
Theoutput of Pin1andRFmeter output arecombinedinthe diode,then itissent tothe front CPUtodisplay the meter.Theoutputsignal of Pin1isfedtoPin6of IC14:A. Thevoltageof Pin5 isdeterminedbythe squelchVRof front unit.Comparingwiththisvoltage,the squelch isopenedor closed.Whilethe checkoperation the CPUoutputdecreasesthe voltageof squelchVRinfrontsideto openthe squelchforcedly. Thesquelchoutput controls IC13, atthe sametimeitisprovided tothe frontunittolightRXLEDand led toCPUunit.
m. NoiseBlankerCircuit
This circuit eliminates the pulsenoise of acar, etc.Becausethe noise emitting
time isshort,inthisdurationthe operation of receiverisstoppedtoprevent the unitIromemitting anoise.Thepulse noise isdelayedwhenitispassedthroughthe narrow band filter,and the emittingtime becomeslonger.Itmakes difficult toeliminatethe noise, soitisnecessarytoeliminate thenoiseinthe earlier stage.Apartof the secondmixer output,whoseband widthislimited,isamplifiedinQ20,
Q19, 018,andQ16. Thesignal isdetectedinD33 andD34, and the AGCvoltage
isapplied to019,Q18and Q16.Thechargetime constant of thisAGCisdetermined by R82 and C128, andalso the dischargeconstant isdetermined byR81+R82, C128. Thevoltageof AGC
doesnot rise suddenly becauseof the chargeconstant, sothat thisvoltageisnot
applied toalmost allthe short signalssuch as pulse noise,butisappliedtothe
continuous signals suchas receiving signal and amplilier gainisdecreased.
Whileemittingthe pulse noise, the AGCvoltagedoesnot followthe pulse noise,
Onthe contrary, as forthe continuoussignal, the detectedvoltageof D33andD34
isfixed by AGC, so015isturnedOFFbecauseof the emitter bias of R85 and
R84.
NamelyQ15isturnedONonly the time of the pulsenoise, then021 isturnedOFF. ThesourceofIFamplifier of 022isbiasedthrough R98 and R102sothatthe gainis decreasedandthe signal isblanked. Whenthe emitter of Q15 is
R388 forthe microphone which needsthe power supply, (solderbridge)InSSB/AMmode, Thegain of IC21(approx. 15dB) isdeterminedbyR329 andR328.InFMmode, R330 isconnectedtoR320 inparallel byQ55, then the gain is
increased approximately 34dB.Alsothe cutoff frequencyisrisen,andthe signal
ispre-emphasizedand operatedas alimitter.Inthe SSB/AMmode, C345 andR384 areconntected tothe feedbackcircuitbyQ63 when the speechcompressor isturnedON. Thegain isincreased about 15dB,thenIC21:B isoperatedas the limitter.Whenthe speechcompressorisON, the low frequency iscut by C345.
InFMmode, the gain isrisen enough, sothe speechcompressorhas no effect.Theoutput ofPin1ofIC21:Bisattenuated inR326 and R325.Thesubaudibletone fromPLLunitisapplied throughR325. (WhentheToneisON.)
This signal isoutputtoPLLunitas the FMmodulation,and output tothe balanced
modulationof IC2.
TheoutputtoIC2ismutedby Q54 inCW/FMmode.
b.BalancedMixer
c. IFFilter
!C2 isthe balanced mixer,and the carrier issuppressedinSSBmode.Toget
moreratioof carrier suppression, the balanceadjustment ofVR3andVR4areapplied.
Thecarrier isnecessaryinCW/FM/AMmode, so the inputof Pinl ismadeunbal
ancedbyapplying the DCvoltageto obtain the carrier.Byapplying the DC inAM/FMmode,orbykeying inCWmode, the balance isbroken toobtainthe carrier wave. VR11isusedfor the adjustmentof carrier level. Inthe AMmode,the DC and modulation isadded simultaneously. InSSBmode, the modulation isaddedbyR317. InAMmode, D93isDC-biasedandturnedON. Thenthe attenuatorconsisting of R317 and R393limitsthe modulation.
After the outputof !C2increasesthe impedance inC177andL77, itispassed throughD49andled intoband limitIFfilter.D52isisolatedhighlybyconnecting to
theoutputinparallel at receiving.InSSBmode,the output isDSBsignal.(Double
SideBand)Thefilterisswitched bythe selection of above-mentioneddiodeswitch.Thesignal ispassedthroughthe following filerineachmode.
SSBisobtained byeliminati'ngoneof sidebands of DSBthrough thefilter.
d.IFAmplifier,TheSecondMixer
After passing throughthe filter,the signal isled toD37, Q7, and D6, and passedthroughthe secondmixerinthe opposite directionofthe receiving,then the signal of71.75MHzisobtained. Q6 operates the CWkeying.Thevoltageof ALCisaddedtothe secondgateofQ7.Thelocaloscillating signal of 71.295MHzand unwanted signal areeliminated in
FL1:AandFL5. Thesignal isamplifiedin05,passedthroughFL5, then led tothebalanced mixer of Q3and Q4.
e.TheFirstTransmittingMixer
f. PowerAmplifier
2)PAUnit
a. PowerAmplifier
b. FinalStagePowerAmplifier
Thismixeristhe balancedtype, and the unwanted signals(IFandlocal oscillating
signal) aredecreased. Thebestoperation isselectedbybiasing the secondgate. Todecreasethe spurious, the signal isbalancedinVR1.
Passing throughtihemixer, thetransmittingsignal which has the desiredtransmit
ting Irequency is passedafter switchingthe LPFtorHFbandor BPFtor50MHz
band. Theunwantedsignal andespeciallythe leak of localoscillating signal is
decreasedas lessas possible.
Thesignal isamplifiedupto0~3dBm inQ1.Tnotch filterconsists of C1,C2 and
11.Itistunedto approximately 44MHz while using 50MHzband todecreasethe
spurioussignal. Thenthe signal issupplied to PAunit.
Thesignal inputtoPAunitisamplifieduptoapproximately 100mW. Theidlingcurrent of 0601 flows about 100mA duringtransmittingasA-classamplifier. The
frequency characteristics are compensatedbyfeedback, besidesconnecting thecapacitor toemitterresistor inparallel.Thesignal isamplifiedupto 10WinQ602andQ603.
PAamplifieristhewideband rangefrom1.8MHzto50MHzTheidlingcurrentflows 100mA (adjusted inVR601), and the amplifier isthe push-pulltype.
Theheat ofQ606 andQ607isdetectedby the thermistor TH601,and the faniscontrolled. While transmitting,the resistancevalue isdecreasedbythe risingof the temperature, then thevoltageofinverting inputterminalof IC601A/Bisdecreased.Non-inverting inputisappliedwiththe voltagecorresponding to thetemperature.When the temperature goesuptoabout 50°Cor moreand the
comparedvoltagebecomeslower thanthe invertinginputvoltage, Q607 isturnedONbythe outputvoltageof comparator, 10601:A. Then the fanstarts turningat a lowspeedby thevalue of seriesresistor(R639).Whenthe temperature rises more and the voltagebecomesmuch lower thanthe comparedvoltageIC6Q1:B,Q608is turnedON. ThenR639is turnedOFFandthe fanturnsata highspeedaccording tothe value ofseriesresistor of R640 todecreasethe compared voltageof IC601: A.Whenthe temperature goesuptoabout 100°C andthe voltageisdecreasedfurtherlower, IC601:Asupplies again, thenR639 andR640areconnectedinparallel toturnthefan ata higher speed.Although ordinary PDWNispulledupto
14VbyR637, the power output issettoLOWbecauseboth cathodeterminalsof D608 becomeLOWwhen the fan turnsat a highspeed. Thenthe signal issent tothemainunitas the control signal for power downathightemperature.Asthe comparedvoltageofIC601:BisdecreasedinD611while receiving,IC601:B doesnot work ifthe temperature doesnotgouphigher thanitwhiletransmitting.Thetemperature, at which the fanturnsat amiddle speedor more, ishigher thanitwhiletransmitting.At hightemperature, fan'sturningspeedcomesdownwhiiereceiving.
d.ProtectionCircuit
e.CWKeyingCircuit
Fortheprotectionof thefinal power amplifier, the followingsare equipped:
SWRdetectionProtection againstovercurrentPowerdown circuitfor the temperaturedetection
Asthe basevoltageof mainunit049goesdowntoLOWbyCWkeying, the voltageissupplied tocollector. This outputcontrols allof thecircuitoperation by
CWkeying.Thecollector output of 049ispassedthroughD95, VR11andD93, andthe balanceisbroken byapplyingDC voltagetothe balancedmixer to generatethecarrier.VR11determines the CWwaveformof rise and fallbyadjustingthe carrierlevel inR285 andC248.
At the sametime Q48isturnedONtoturnOFFQ6for keyingisolation. C244 makes the OFFtimeof 06longernot toinfluence the keyingwaveform.Thevoltageisapplied to IC17: BPin5 inD95,andthe outputof Pin7turns046ON to setPTTlinetoLOWinD73,then the unitenters the transmittingmode. Thecapacitor (C246,C247)is connectedbetweenPin5 of IC17: Bandthe ground.Theholdingtimeoftransmittingisdeterminedaccording tothe discharge timeconstant. BK1,BK2, and BK3arethe voltagestorthe settingof 3*bitbreak-in timeconstant. 8 stagesvoltageisobtainedbythe combination ofthe resistors R269,
R270 andR271.Inthe FullBreak-inmode, allof BK1,BK2andBK3 are settoLOW, inthe Semi Break-inmode, oneof BK1,BK2, or BK3isapplied the voltage.
Whenallof the breakers areapplied the voltage, itisusedasthe shortest time
constant.Wheninthe fullbreak-inmode, allof the voltagesof BK1, BK2and BK3arelowlevel, andQ47 isturned OFF. Thereforeonly C246is the veryshort discharge constant, itisthe fullbreak-in mode withshort transmittingtime. Oneof BK1,BK2andBK3 issupplied the voltage, andQ47isturnedOFF, thenconnectedto C247
andC246 inparallel. Thedischarge time constant islonger, and itisthe semi
break-intime constant.
Thereare7stagesofthe voltageinthe semi break-in modeaccording tothe outputvoltageof BK1,BK2 orBK3.This isapplied to the comparedvoltageof
appliedtoallof BK1,BK2 andBK3, the time constant is the shortest.
When the break-in modeissettoAUTO, BK1only issupplied, and the compared voltageof IC17:B iscontrolledbytheoutput voltageof IC17: B.Inthe AUTOmodethe keying outputisemitted byone-shot multivibratorconsistingof IC18Aaod Bwheneverthe keyispressed. Thereforethe averagevalueotthe outputvoltageof IC18: Aisinproportion tothe averagespeedof keying. To obtainthe averagevoltageinR281,C245, etc., integratethe voltage. ThenthisoutputisD/Camplified in!C17:A, andprovidedas the comparedvoltageofkeying.
D97isused for OFFinthe AUTOmode. Whenthe AUTOmodeisinthe LOWlevel, the voltagechargedinC245isshort,then the operation inAUTOmodeisstopped.D107andR360 are usedtogetupspeedrisingwhen the keying isstarted. D92andR280 determine the discharge time constant. While receiving the timeconstant isprolonged.The selectionof transmission/reception follows the keying speedfrom30 letters/minuteto200letters/minute.The transmittingmodeisheld betweenletters,andthe unitreturnstoreceiving
mode betweenwords.
f. PowerControl,ALCCircuit
Theforward wavevoltageinproportiontothe transmittingpowerobtained infilterunitisinverting-input to IC8A,andinverting-amplified. Non-inverting inputisapplied the voltage,andthe outputvoltageisshifted bythe non-inverting inputvoltage.ALC line isapplied the voltageof about 2.7Vbeforehand,andthe ALCvoltageissupplied tothe secondgateof theamplifier.When the forward wavevoltageisdetected, the output voltageof IC8:Aisdecreased. Ifitisabout 3Vor below, the ALCline voltageisdecreasedby D63.VR7 isused for theadjustment of 100W. Whentheunitisswitchedto50WbySi,Q27isturnedONandVR5isconnectedinparallel to decreasethe voltage, thentheunitisadjusted to50W.
InAMmode,R195 isconnectedinparallel todecreasethe voltageupto about 40W.Inthe iow power mode, R191isconnectedinparallel bysetting toLOW, andthevoltage isdecreased.029andVR8areusedfor the adjustment to getthe required powerof about 10W inthe matching operation ofexternal automatic tuner.(Therequired power dependsonthe tuner.)When the value of SWRishigh,thereflectedwavevoltageturnsQ28ONtodecreasethepower.Theunitisoperatedwhen the SWRisabout 3 or more.
Comparedwiththeforward wavedetection powerinHF band of100W,theforward wavevoltagein50MHz band of 10Wissettohigher a little.InSSBmode, "fast attack"is obtained byD63, andthe releasetime of "slowattack" is obtained byC222 and R130. InAMmodeC221isconnectedinparallel by Q30, andtheunitisoperatedinnear the averagevalue.
quencyisdivided by10inIC19of the mainunittoobtainthe sidetone of 650Hz~
850Hz. Thecomparison frequency of thesecondlocaloscillator ischanged
according tothe CWoffsetsetting.Torelate withthe sidetone, comparison
frequencyisabout 100times the CWoffset. IC19Pin2iscontrolledbyQ65 at CW
keying.Thetimeconstant isdelayednot to givetheinfluence towaveformofthe
sidetone.
Thefollowing activefilterQ50 makes thesquarewavetosine wavetoobtain
bettersound. Therise/fallwaveof the sidetoneisgeneratedbykeying controlling
the bias of baseandemitter.
Whenusing theexternal automaticantenna tuner,thiscircuitcontrolsthe matchingstart signal andthe operationof theunitduringtunermatching.Whenthe tuneoperation isstarted, the Tunevoltageissupplied tooperatethe one-shot multivibratorinIC18:C,D.The voltageof about 8V isapplied to outside for afixed time throughQ52 asthe start signal. Inthe other hand,Q53supplies the tunevoltageof sinkoutput,itbecomesLOWwhile tuning.(Forthe transceiver madeby ICOM, KENWOOD).Assoonas the tunerreceivesthe tune start signal,the tunerprovides itas the tuningsignal.(TKEYterminal)
CPUobservestheTKEYterminal, andkeepsthe unitinTUNEmode indicatingthat the tunerisoperating while itisinthe LOWlevel. CPUreleasesthe TUNEmodewhenTKEYterminalisinLOWfor 20secondsor more. Inthe Tune modetheunittransmitsa signal inAMmode, the microphoneoutput ismuted, thenthecarrier iskept onoutputtingabout 10W (adjustable).
k.RegulatedPowerSupplyCircuit
I.ModeVoltage,FunctionControl(BPF/LPFSelector)
ICt1isthe BVRegulatedPowerSupply Circuit.T8Vthat isnecessarytor transmittingismadein033,and R8Vthat isnecessary(or receiving is madeinQ35.
IC10,032and034control the transmission/reception. WhenPTTlineiscon
Hlevel issupplied fromIC10: AanditisledtoCPUof front unittodetectthe
transmission/reception switching.
IC10:C delaysthe rise of receiving inR227, C224 andD62 and controls inQ32andQ33.While receiving,the currentisflowing from 13.8V through R230 and D75, thenthe
While transmitting,the basevoltageofQ33is OVbecauseQ32isturnedON, and
R8V isnot provided.While transmittingR8V isshort byD77, anditmakesthe chargevoltagesuch as electrolytic capacitor dischargemomentarily not toremain R8V.As for 035,as sameasR8Vthe current isflowing from 13.8Vthrough R230 and
D75,then the basevoltageof Q35 isapproximately 8.7V and the emitter output is
just8V while receiving. Whiletransmitting,the basevoltageisOVbecause034is
The enableterminals ofIC15andIC16 selectthesignal ENX or ENYby using
IC24andQ62.The data fromCPU(DAT2)consists of 16-bitserialdata, two8-bitshift resistors areconnectedinseries.IC22andIC23 control the bandselection, ON/OFF of preamplifier, ATT, power, TX mutefunction,,etc. TheyareoperatedinLowlevel.IC15controls the Modevoltage,andIC16 controls filter,AGC, Break-in, PTTlock,andNoiseblanker. Thevoltageo1everymode(USB, LSB, AM,CW, CWU, CWL,
FM,TUNE) turnsON041,Q42,043andQ44 tosupply 8V .
m-LPF
HFsupplied fromPAfinalstageeliminates harmonics through LPFof filterunit.
Input/Outputofthisfilterisswitched bythe relay, and Input/Outputof unused filter
isshortatthe relaycontact.
LPF control isusedthe BPFcontrol voltageofthemain unit.EveryLPFconsists of Chebyshevfilter,and double or moreharmonics areattenuatedabout 40dBor more.
50MHz bandperforms the transmission/receptionselectionbythe diodeofD508and D509.Itissupplied to antenna terminalof 50MHzthrough LPF.BothD508andD509are turnedOFFwhile receiving,the receiving signal from theantenna terminal ispassedthroughLPF(L520, L521,C570-C574, L518, C565)and HPF(L516,C562~C564), thenamplified in0503.
0501and0502 are turnedONwhile transmitting,and D508and D509 areturnedONthen the transmittingoutputispassed.Theantenna inputof receiving circuit isshort becauseD509 isturnedON. Alsoas
the parallel resonant circuitconsists of L518,D508,etc., the transmitting signal
doesnot influenced.
TheeachpowerdetectioncircuitisequippedwithHF band and 50MHzband.
Theharmonicsare sometimesgenerateddependingon the using diodeinthe
detection circuit.LPFmakes the standing wave,sothe circuitislocatedbeforetheLPFin50MHz bandwhosespuriousspecification issevere,andafterLPFinHFband.From nowonthe operation inHFband isshown, andin50MHzband the operation is the same.L534 is10-turnbifilarof toroidal core(twisted pairs of AWG).Thereforethe bothsidesare20 turnswithcentertap.Piercing the center holeof the coremeans the samewith1turn.Sothe transformer is1:20.ThereforeR508 isappliedthe voltage(forward wavevoltage)accordingtothe outputvoltage,and R509 isapplied the voltage(reflectedwave)according tothe
reflectedpower. Theoutput power and reflectiondetectthe powerto control the power inthe main unit.
Thepuise generatedbythe rotationof the main dialiseliminated the chattering inIC1001: A, B.IC1001:AandBarethe Schmitt triggers bythe feedbackfromtheoutput.Therise and fallof eachoutputisdifferentiated in!C1002:A, C, sothe pulse number isdoubled. Thenitis4timesthe pulsenumber becauseofsynthesizing in
IC1001: C.
Tofindthe rotationdirection, itisdetectedin1C1002:B andIC1003 and fedto
CPU. AsS1002 generates50 pulse at 1rotation, what isinputtoCPUis200 pulse/rotation,and5kHz/rotationin25Hzstep.Themain dialrotates veryfast and generatessomany pulses. Thepulse isdivided inIC1004, andthe pulse number is storedasthe 6-bitbinarydigit byeachdividing output.At ahighspeedrotation the frequencyis forwarded bycounting the pulsenumberstored inIC1004, then the processisfinished, the pulse number
When SW1001 ispressed, Q1001isturnedON, thenthe contactof RL602 inPAunitisturnedONtosupplythevoltageof 13.8Vtothe front unit.Oncethe CPUstartsoperation,theoutputfrom PCONTof CPUturnsQ1006ONtoholdONtherelayof RL602.When SW1001iskeptpressing while the power isON, the signal isdetectedin
PSDET, and the 01006isturnedOFFtocutOFFthe powersupply.
b. PowerSupply
c.DimmerCircuit
d. LCD
e.Others
1C1007isthe regulated powersupplyof 5Vwhich has the output for CPUreset.
IC1006isthe regulated powersupplyof 8V which generatesthe requiredvoltageforIFshiftand volume control.When the powersupplyiscut OFF, the output of regulated power supplyof8Vis
increased first,anditisdetectedinD1018 andIC1002:D, thensenttoCPU. In
CPU the dataisstored inthe EEPROMof IC1005beforethe outputof regulated
power supply of 5Visdecreasedandthe unitisreset.D1019 andC1002 areused
to holdthe output voltage of5V bykeeping the inputvoltageof 5V regulated power
supplyas longas possible.
Theregulated powersupply olabout 10.5V consistsof Q1003,Q1004 and Q1005.
Q1003 supplies about 10.5Vwhen the DIMMoutputfromCPUis5V.InCPUunit,DIMMisthe pulseoutput,and itswitches ON/OFF of the output of about 10.5V.Atfulllightingthe outputfrom CPUisfixed to5V. In’'LP4"modethe dutyis80%andin"LP3 " modethe dutyis60%. Inthisway the brightness ischangedbythedutyinQ1003.Q1003issupplied the current by turningON/OFF.At the maximumthebrightness isthe lightest, andthe dutyisdecreasedaccording tothe dimmer,thenthe powerdissipation isdecreased. Thedimmercan beoperated bythe smalltransistor.The maximumbrightnessis10.5V,and itissettounder the regulation voltage
(5.3V x2) toprolong the life of thelamp. Therushcurrentwhen thelamp isturnedONisinpulsemode todecreasetheload onthe lamp.
Theindicationsuchas frequencythatisrequiredthe speedisperformedbytheCPUitself, andthe other indications areperformedby the LCDdriverof1C1009.TheLCDindicationemploysthe frame frequency of about 128Hz, 1/2DUTYand1/2bias.
X1001isthe ceramicresonator of8MHzselectednot toenterthe amateur band intheharmonics relations.When the powerisON, the voltageissupplied fromY2andY3, todetectwhether
ThebothsidesofRITVRareapplied5V, andthe location of VRis detectedbythe
voltageof A/Dinputterminal.
Inthe ReceivingfrequencymonitorQ1019 isturnedONby the MONI outputfromCPU, the squelch setting voltage programmedby turningthe knobon the frontpanel isdecreasedforcedly. Thenthe squelchisopenforcedlywithout any relation withVRposition.Theoutputfromthe mainunit(RTXC)lights the LEDaccording tothe changeofthe ALCvoltage. Theoutput cannotbesupplied as itis,soitischangedto ON/OFFsignal inQ1009.Q1011isthe squelchoutputfromthe main unit,anditlightsRX LED.
Thefollowings areperformedinPLLunit:
Thegenerationof carriersignalThegenerationof the firstandsecondlocal oscillating signal Thegenerationof sideloneCTCSS
Adding the FMmodulationMakingthe power supplyof 5V
Powersupplydependingonthe MODEcomesfrom the main unit.
(2) Firstthereferencesignal of 30MHz isgeneratedinX701and Q701according
tothe constant of TC701 andL702.
(3) Secondlythe signal of 9.420MHz +/-1.5kHz isgeneratedbythe voltageof
D706inX702, 0721 andQ722.
(4) Thirdlythesignal of 9.875MHz +/-1.5kHz isgeneratedaccording tothe
constant of TC702-TC704, C807, C809, C810, C811and C812inQ725 andQ724.
(5) Thefrequency of9.875MHzischangedaccording to the MODE, transmission/
reception.
[Transmission/Reception of LSB]CN701 Pin21(LSB)isapplied the voltageof 8V andthe signal ispassedthroughD714,thenresultsinthe frequency of9.8735MHzaccording tothe constant of TC702and C812.Also(LSB)8V ispassedthroughD718, and the voltageisapplied toQ723 toemit the carriersignal.
[Transmission/Reception of USB]CN701Pin26(USB)isapplied the voltageof 8V and the signal ispassedthrough
D711,thenresultsinthe frequency of 9.8765MHzaccording to the constant of
[Transmission of AM/TUNE]CN701Pin22(AT)isapplied 8Vandresultsinthe frequencyof9.875MHzaccordingtothe constantof TC703,C811.Thevoltageof 8V fromCN701 Pin23 (T8V)ispassedthrough D718 to add the voltagetoQ723,thenthe carrier signal isemitted.
[Transmission of FM]CN701Pin20(FM) andCN701 Pin23(T8V) areaddedthe voltageof8V,the Q729and Q733areturned ON, 8V voltageof CN701Pin20(FM) is passedthroughD708,0733andD714, then resultsinthe frequencyof9.8735MHz according to the constant of TC702andC812.HereFMispassedthroughATand
R814 to turnONC811,however, as Q733 isalsoturnedON, 0727isturnedONandC811isshorted.
Thevoltageof 8VfromCN701 Pin23 (T8V) ispassedthrough D718, andled to
Q723 toemit the carrier signal.Thevoltageof 8V fromQ733turnsONthe analogueswitch ofIC715.Themodulationsignal ispassedthroughR798, IC715, R796 and C801,anditisFM-modulated inVC02.
resultsinthe frequency of9.875MHzaccording tothe constant ofTC703andC811.Although here CWUtriestoturnC810ONorCWLtriestoturnC809ON, itcannotbedonethrough 0715becauseQ729 is alsoturned ON.
[TheReceptionof CWU]
CN701 Pin24 (CWU)issupplied the voltageof8V, passedthroughD712, then
resulting inthe frequencyof 9.8758MHzof frequencyaccording tothe constant of
throughD716and D717to the Q723, thenthe carrier signal isemitted.
[TheReceptionof CWL]CN701Pin25 (CWU)issuppliedthe voltageof 8V, passedthroughD712,then resultinginthefrequencyof9.8742MHzoffrequency according to the constant of TC7G3andC809. Alsothe voltageof 8Vfrom CN701 Pin25 (CWL)ispassedthroughD716andD717tothe Q723, then the carrier signal isemitted.(6) Thefrequency of 9.42MHzcanbechangedonly while receivingbythe IFshift
volume onthe front panel.
Thevoltagesupplied toCN701 Pin14 (SHV) ischangedbytheIF shift volume, and
the capacitanceof D706isalsochanged, then 9.42MHzischanged. Thecenter frequencyof the IFshiftvolume isdetermined byVR702.Whiletransmitting0715isturnedONbyT8Vto eliminate the influence bySHVandVR701,thenthe frequencyisdecidedonlybyVR701.
InUSBCN701 Pin26(USB) andCN701 Pin15(TONS)aresupplied the voltageof 8V.AsinUT modeTONSbecomesthe sink,0735isturned OFFandUSBissupplied 0V,thenQ730 isturnedONand a terminal of R767 isconnectedtotheground to decreasethe voltageofD706, besidethe frequencyof 9.42MHzisdecreasedabout 300Hzlesswhile receiving andabout 100Hzlesswhile transmittingthanthe vaiue inUSBmode.
(8) TheSecondLoca!Oscillating SignalInVC02unit,after the frequencyof 71.295MHzisoscillatedin0941 andamplifiedin0949,Q944 andQ945, the signal ofapproximately 3dB issupplied to MAIN unitthroughJ702as the secondlocal oscillating signal.Thesignal for PLLloopissupplied from Q942 to PLLunit.Thesignal of 71.295MHz isfedto Mixer IC711Pin7 and thesignal of9.42MHz isfedto Pin3, sothat the deferencefrequencyof61.875MHioutputfrom Pin6 onlyis
pickedupby Q711,L712andL711,andfedtoPLLIC707, then locked at
61.675MHz.Therefore, by rotatingthe IF shift volume, 9.42MHz, and also71.295MHzare changed.Thefrequencyof 30MHz isfedto IC707through Pin1,anditisdivided to getthe following frequencyasthe referencefrequency, andalsothe frequency of
61.875MHzisdivided togetthe referencefrequency, then thesetwofrequencies arecompared.Thereferencefrequency changesaccording tothe CWsidetonefrequency.
Whenthe sidetone frequencyis650Hz, the referencefrequencyis 64.655kHz. When the sidetone frequencyis750Hz, the referencefrequencyis75.000kHz. When the sidetone frequencyis850Hz, the referencefrequencyis85.227kHz.
(9) TheFirstLocal Oscillating SignalInthe HF mode, the frequencyoscillated inVC03isamplifiedinQ710andQ714,andpassedthroughthe switching diode D725 and D726. then band-passfilterandRL701.The signal of approximately 3dB isled tothe MAINunitfrom J703.
3VCO'sare builtinVC03,anditisoscillatedunder following frequencyconditions:
Whenthe frequency is50MHz,inVC03theoscillatedfrequencywithin76.75-
80.75MHz byD961,TC961 and 0961 aresynthesizedwiththe frequencyof 45MHz bythe DBM(DoubleBalanced Mixer) inL729,L730andD730,then thefrequency within121.75-125.75MHz isgenerated. Itispassedthrough RL701bytheband-passfiltersof L732,L733.L734andL735 and Amplifier of0731and0716, thenthe signal of approximately 3dBis output toJ703.The frequency of 45MHz isgeneratedas follows: Thereferencesignal of30MHz isamplifiedin0719andfedtoIC701Pin3, thenonehalfof the signal issuppliedfromPin5. 3 timesfrequencyof thesignal only ispassedthroughthe filter L720,
L721and L722,andfedtothe center tapof L729,then led to DBM.
Thefrequency loop of VC03islockedasfollows: VC03oscillating frequencyispassedthrough0712andinputtothe mixer 1C709Pin6,alsothe signal of70.65-
70.75MHz (25Hzstep) isfedto1C709Pin8.Thenthe signal of 1.1-31.1 MHz passedthroughtheamplifierQ713and led toPLL1C702Pin8as the differencesignal.Thisfrequency islockedbythe following procedure.
Therefore, asthe referencefrequency of IC702, the referencefrequencyof 30MHz
isdivided upto100kHz inside theunit.InIC702, the operationfrequency of100kHz or moreonly iscontrolled.
In50MHzband, CN701 Pin1(50M) issink,Q732collector issupplied the voltage of 8V.Thepowersupply of0731, 0716isturnedON. 0709andD730 areturnedON. 0709, RL701, D724and D7'24areturnedON, thenD730 isONandQ724 isOFF.Thedeviation while transmittingis5kHz/DEV, and2.5kHz/DEVwhile HF/FMtransmitting.
Inthe HFmode, Q717isON, andD725andD726areturnedON, then D735isON. IC710Pin4issupplied about 0.7V sothat the operationof IC710 isstopped.
Whenthe unlocksignal isemitted fromeveryPin7inPLL IC IC702, IC703 and
IC707, the voltageof 8Vissupplied fromthe collector in0728,and0718isturned
ONsothat0714isturnedOFF, then the level of J703 isdecreasedabout 30dBor
more.
(10) 25HzStep70.65-70.75MHzInVC01Unit,togenerate25Hz stepof thefirstlocal oscillating, 0931isused tooscillatethe frequency of 155MHz~175MHz, the signal ispassedthroughQ932 and divided by20inIC704, andsupplied throughQ933. Thenthe signal isdivided by10inIC705, andthefrequency of 775~875kHz(25Hzstep) isfedtothe mixer
IC701,Therefore, the operationfrequency of 100kHzdigitor belowcanbe operatedin25Hz step.Alsothe frequency isinputtoPLLunitIC703 Pin8throughQ931for thePLLloop.PLLICdivides the frequency of 155.000-174.995MHz toget5kHz,anditiscomparedwiththe referencefrequency of5kHz tomake the loop.
30.1MHz
Indicationofthe operationfrequency Oscillating frequency
of 100kHz digitor below
.0000(00)
.5000(00)
’Thenumberin( )isthe frequency of noindication.
Thereferencefrequency of30MHzisdivided toget5kHz (25Hz x200), andused asthe reference frequencyinIC703. Becausethe signal of 9.875MHz isinputtoIC701Pin8,thesum of the frequencies,10.65-10.75MHzissuppliedfromIC703Pin2, and passedthroughthe ceramicfilterof 10.7MHz, then fedto IC706 Pin6.
Asthe double harmonics of referencefrequency of 30MHzare generatedinQ708, L710 andL709,andthey arefedto1C7D6Pin8.Thesumof thefrequencyof
70.65-70.75MHz issupplied fromIC703 Pin3. passedthroughthe band-pass filterof L706, L707and L708, andfedto IC709 Pinpari of the loopof the firstlocaloscillatingsignal.
.9999(75)
8.Thenthe signal isncludedina
155.000MHz
165.000MHz
174.995MHz
(11) CTCSStoronly FMtransmissionInToneunit,Ttypecontrols the frequency withthe DIP Switch SW901 Pin3- 8,thenitisoscillated between67-251Hz,amplifiedinQ901andpassedthroughCN704-1, thenled tothe MAINunitfrom CN701Pin16.Inthiscircuit,ONoperationisperformed when TONSisthe sinkand IC901Pin4isOV,and FMissupplied 8V andtone unitpower supply isON.Thetonelevel iscontrolled withthe DIPswitchSW901 Pin1andPin2 toadjust the