Kenwood TS-990S Service Manual

Also see for SP-990: Instruction manual

Contents

TS-990S7Fig. 3 Frequency configuration of the transmission and sub receiver blocksCIRCUIT DESCRIPTIONAD9835DDSADF4001PLL PLLADF4001FMODR40MVCO40MHzFM IC455kHz3rd IFAFADC/DACDSPAF OUT1st IF 2nd IF1st IFDDSAD9951PLLADF4111VCOx2x2x2TXMIXRXMIXRXMIXIFAIFBAD9835DDSRXMIXTXMIXFM24kHz24kHz10.695MHz73.095MHz11.374MHzSUB RX IFB (To Scope unit)SUB RX IFA/TX (To Scope unit)MIC INexcept FMTX/RXMIX15.6MHzANT2-2. Reference Signal GeneratorThe frequency of the voltage-controlled crystal oscillator(VCXO: X1 and Q13) is locked to 15.6MHz and used as areference frequency for the transmission and sub receiverblocks. The 15.6MHz signal is applied to pin 5 of the PLL (IC1)via the buffer (Q19) and amplifier (Q2). The signal which isapplied to pin 5 is divided by N, and the 40MHz referencesignal which is applied to pin 8 is divided by R. These sig-nals are phase-compared to lock the VCXO frequency at15.6MHz. The phase-locked 15.6MHz is frequency-doubledby the multiplier (Q34) to generate 31.2MHz.The 31.2MHz is used as a reference signal for the DDS(IC12) for the 3rd local oscillator (SLO3) and the DDS (IC11)for transmission 1st local oscillator (TLO1). The 31.2MHz isfrequency-doubled by the multiplier (Q50 and Q52) to gener-ate 62.4MHz, and is used as a reference signal for the PLL(IC10) that generates a reference signal for the receiver’s 1stlocal oscillator (SLO1).2-3. TLO1/SLO1/SLO2/SLO3■ TLO1 (1st Local Oscillator for Transmission)The DDS (IC11) outputs a frequency ranging from 8.33 to8.47MHz in reference to the 31.2MHz. It passes through theceramic filter (CF1) and is applied to the PLL (IC16). The 8.33to 8.47MHz is divided by R by the PLL (IC16) and is used fora phase comparison frequency (fø).The VCO (Q17, Q18, Q39, and Q40) of TLO1 oscillatesat frequencies ranging from 73.125 to 133.125MHz. It is ap-plied to pin 5 of the PLL (IC16) and is divided by N inside thePLL.The phase comparator inside the PLL compares thephase between fø and the frequency divided by N, andgenerates the phase-locked oscillation signal for the TL01.The output signal from the VCO (Q17, Q18, Q39, and Q40)is amplified by Q56, passes through the BPF, ATT and LPF,and is sent as the TLO1 (73.1 to 133.1MHz).■ SLO1 (1st Local Oscillator for Sub Receiver)The VCO (Q16) oscillates at 393.6MHz. It is applied topin 5 of the PLL (IC10) via the BPF, and the 62.4MHz whichis obtained by multiplying the 15.6MHz reference frequencyby 4 is applied to pin 8. The signal input to pin 5 is dividedby N and input to pin 8 is divided by R. They are phase-compared to phase-lock the frequency, which is used as areference of DDS (IC14).The DDS outputs the 13.17 to 32.88MHz with the IFBselected. It is amplified by the wide-band amplifier (IC15),and output as an SLO1 via the BPF. The DDS outputs the36.56 to 66.55MHz with the IFA selected, and is amplifiedby the wide-band amplifier (IC15). The output is frequency-doubled by the multiplier (D19), and is sent as an SLO1 (73.1to 133.1MHz) via the BPF.■ SLO2 (2nd Local Oscillator for Sub Receiver)The SLO2 outputs a 62.4MHz signal which is the15.6MHz reference frequency multiplied by 4.The 15.6MHz which is sent from the reference oscillationis applied to the frequency doubler (Q34) via the buffers (Q19and Q25), and 31.2MHz is generated. The 31.2MHz is fre-quency doubled by the multiplier (Q50 and Q52) to generate