Kenwood TK-5710 Service Manual

Also see for TK-5710(H): Instruction manual Specifications Instruction manual Instruction manual Instruction manual

25TK-5710(B)/5710H(B)CIRCUIT DESCRIPTION1. OverviewThis transceiver is a VHF/FM/APCO portable transceiverdesigned to operate in the frequency range of 136 to174MHz.Fig. 1 Frequency configurationANTTX/RX : 136~174MHz185.95~223.95MHz136~174MHzPAAMPTXAMPMICAMPVCXO16.8MHz50.4MHzx3ANTSWRFAMP1st MIX49.95MHzMCF SPMICCF450kHzMIXIF AMPPLLVCOFPGAA/DD/ADSPAFAMPThe unit consists of receiver, transmitter, phase-lockedloop (PLL) frequency synthesizer, base band parts, powersupply, and control circuits.2. Frequency ConfigurationThe receiver is a double-conversion superheterodyneusing first intermediate frequency (IF) of 49.95MHz andsecond IF of 450kHz. Incoming signals from the antenna aremixed with the local signal from the PLL circuit to producethe first IF of 49.95MHz.This is then mixed with the 50.4MHz second localoscillator output to produce the 450kHz second IF. Thissignal is detected to give the demodulated signal in the DSP.The transmit signal frequency is generated by the PLLVCO, and modulated by the signal from the DSP. It is thenamplified and fed to the antenna.3. Receiver System3-1. Front-end RF AmplifierThe receive signal from the RX terminal (CN200) of the TX-RX unit (X57-703) is amplified by a transistor (Q200) andpasses through the band-pass filter (L221, L222, L223) toremove unwanted signal.The signal passing through the band-pass filter goes intothe 1st mixer.These band-pass filters are tuned to a desired frequencyby variable capacitance diode (D200, D201, D202).A tuning voltage corresponding to the desired signal isapplied to each variable capacitance diode to tune to thereceive frequency.3-2. 1st LocalThe 1st mixer uses double balanced mixer (A400).The receive signal passing through the band-pass filter(L221, L222, L223) and the 1st local signal generated by theVCO, are mixed by the 1st mixer (A400) to produce a 1st IFsignal (49.95 MHz) (Upper heterodyne).Fig. 2 Front-end RF amplifier and 1st local1st IF49.95MHzRX terminal(CN200)136~174MHz1st Local OSC185.95~223.95MHzVCTUNEVCOD200,D201,D202RF AMPQ200Local AMPQ201BPFL221,L222,L223LPFLNA1st MIXERA400