Kenwood TS-950S Service Manual

Also see for TS-950S Digital: Instruction manual Instruction manual Instruction manual Instruction manual Service manual

TS-9505/SDCIRCUITDESCRIPTIONMode Display frequencyUSB, LSB ! Carrier point frequencycw Transmit carrier frequencyFSK Mark transmitter frequencyAM, FM IF filter center frequencyTable 1 Display frequency in each modeFSKtransmissionisnormallyperformedintheLSBmode.Theaudiosignal(mark=2.128kHz,space=2.294kHz)isobtained bydividingthereferencefre-quencyfSTo.TheIFsignalisshiftedforbothtransmis-sionandreceptionsothatthemark/spacesignalpassesthroughthecenteroftheIFfilter.ThefML1signalisshiftedintransmitinordertodisplaythemarkfre-quencyon thedispiay.FM transmission is performed directly on the fMi2signal by using the microphone audio to modulate theVCOO signal.ForreceptioninAMandFMmodes,thefMclineisshiftedbytheVCO9signalsothatnocarrierenterstheIF.WhentheDSPisconnected,thefmcandfMi4linesareusedasoutputsignalsfromtheDSPunitinthetransmitmode.ModechangesareperformedbythefML3line.TheFSKmodediffersfromtheAFSK modesincethesignalsuppliedtotheIF unitisobtained fromtheDSPdirectly,thereforechangesinthesignalthatwouldnormallybeexpectedduetoachangeinthemodearenotperformed.Sincethereferencefre-quency-appliedtotheDSPissuppliedfromtherefer-enceoscillator(f$Tb) forthemainunit,nochangestotheoperatingfrequencywilloccurwhentheDSPisconnected.+Sub-Receiver frequencyconfigurationTheequationshownbelowholdstruewhenthereceiver is zero beat.fIN = fSL1 —fSL2 + FSC... ee (2)Thecrystal oscillatorsignal(f$L2) isappliedtothePLLcircuitinordertogeneratethefSL1signal.Thesub-receiver frequency,likethemainreceiverfrequencystability/accuracy,isdeterminedonlybythereferenceSTDandthePLLdivideratio.Likewise,whentheunitisusedfortransmissionin(thesubreceiveristurnedoffintheAMandFMmodes),thefrequencystability/accuracyisdeterminedbythereferencefSTDandthePLLdivideratio.Thedisplayfrequenciesinthe variousmodesarethesameasthose describedforthemainfrequency.Sincethesub-receiverworksasatransmitfrequencymonitor, theIFfrequencyisshiftedtothat of themaindisplayfrequencyinthetransmitmode.IntheAMandFMmodes,theIFfrequencyequalsthemainIF fre-quency.PLL CircuitThe TS-950 PLL circuit consists of a several loops(ML.O1, SLO1) that cover a frequency range of 10 kHzto 30 MHz, in 10-Hz steps; a 20 MHz reference oscilla-tor anda PLL loop that is used to generate other localoscillator frequencies (MLO2 to MLO4) and CAR(MCAR, SCAR} signals. Figure 2 shows the PLL sys-tem frequency configuration. Division ratio data foreach PLL loop is provided by a microprocessor. Eachloop is a single crystal frequency control system: wherethe phase is compared with a unique reference fre-quency (fSt0).Figure3isaPLLblockdiagram.+ReferenceoscillatorcircuitThereferencefrequency(fsTD)usedforfrequencycontro!isgenerated bythe20-MHzcrystaloscillatorX1andQ13(2SC2714).Twooutputsareprovided,oneisusedasthereferenceforthePLLunit,andtheotherisdividedinhalfby!C14(M74LS90P)toproducea10-MHzsignal.This10MHzsignalisusedasthePLLreferencesignal(fREF) fortheCARunit,andisappliedtotheAFandDSPunitsasthePLLreferencesignal(fREF).The10-MHzsignalisalsodividedbyfiveinIC14,andthen dividedinhalfbyC15{TC4013BP}togeneratea1-MHzsignaThereferencesignaloscillatorcircuitcanbeusedasVCXO(VoltageControlledCrystalOscillator)byapply-inganexternalreferencesignal.The1-MHzsignalisdividedby100inIC13(MC14568BCP)togeneratea10kHzcomparisonfrequency.The10-kHz(1Vp-p)inputfromtheEXTSTDpasses throughamplifierQ12(2SC2712)andisappliedto1C13whereitisthenusedasthePLLreferencesignal.Itisthencomparedinthephase comparatorinordertolockthereferencefre-quency(fsTo) ofOSC1.Theinternalandexternalrefer-ence frequenciescanbecontrolledbyS1.OSC1canbe replacedwith the optionalSO-1or$0-2TCXO.,ThesearecontrolledbyswitchS2.The20-MHzsignalapplied-tothePLLunitisdividedinhalfbyiC9(SN74LS73AN)toproducea10-MHzsignal.ThissignalisusedasthePLLreferencesigna!(fREF)forthePLLunitandisdoubled byQ4(2SC2714)toproducethe40-MHzreferencesignal(fREF).+MainLO1 (PLLunit/AFunit)PLL3,whichisdownstreamfrom LO1, generatesthe58to56MHz VCO3signal.The10-MHzreferencesignal(fREF)isappliedtopin5of IC2(CX7925B)},andisdividedby 5000internallytoproducea2-kHz compari-sonfrequency. The output fromVCO3isappliedtopin11of IC2,andisdividedbyavaluedeterminedby N3,andisthencomparedwith the2-kHzsignalinthephase comparator. The frequencyofVCO3islocked