Kenwood M) Service Manual

Also see for TK-2160: Specifications Instruction manual Instruction manual Specifications Service manual

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TK-216075) Audio Amplifier CircuitThe demodulated signal from IC401 is amplified by IC602,and goes to AF amplifier through IC601.The signal then goes through an AF volume control(VR801), and is routed to an audio power amplifier (IC605)where it is amplified and output to the speaker.Fig. 3 Wide/Narrow switching circuitCIRCUIT DESCRIPTION1. Frequency ConfigurationThe receiver utilizes double conversion. The first IF is 49.95MHz and the second IF is 450 kHz. The first local oscillatorsignal is supplied from the PLL circuit.The PLL circuit in the transmitter generates the necessaryfrequencies. Fig. 1 shows the frequencies.Fig. 1 Frequency configuration1) Front End (RF AMP)The signal coming from the antenna passes through thetransmit/receive switching diode circuit, (D204,D206,D208and D212) passes through a BPF (L411 and L412), and isamplified by the RF amplifier (Q404).The resulting signal passes through a BPF (L407 and L409)and goes to the mixer. These BPFs are adjusted by variablecapacitors (D402,D403,D404 and D405). The input voltageto the variable capacitor is regulated by voltage output fromthe microprocessor (IC805).2) First MixerThe signal from the front end is mixed with the first localoscillator signal generated in the PLL circuit by Q403 toproduce a first IF frequency of 49.95 MHz.The resulting signal passes through the XF401 MCF to cutthe adjacent spurious and provide the opitimuncharacteristics, such as adjacent frequency selectivity.Fig. 2 Receiver section2. ReceiverThe frequency configuration of the receiver is shown in Fig. 2.3) IF Amplifier CircuitThe first IF signal is passed through a four-pole monolithiccrystal filter (XF401) to remove the adjacent channel signal.The filtered first IF signal is amplified by the first IF amplifier(Q402) and then applied to the lF system IC (IC401). TheIF system IC provides a second mixer, second localoscillator, limiting amplifier, quadrature detector and RSSI(Received Signal Strength Indicator). The second mixermixes the first IF signal with the 50.4MHz of the secondlocal oscillator output (TCXO X1) and produces the secondIF signal of 450kHz.The second IF signal is passed through the ceramic filter(CF401) to remove the adjacent channel signal. The filteredsecond IF signal is amplified by the limiting amplifier anddemodulated by the quadrature detector with the ceramicdiscriminator (CD401). The demodulated signal is routedto the audio circuit.4) Wide/Narrow Switching CircuitNarrow and Wide settings can be made for each channelby switching the demodulation level.The WIDE (high level) and NARROW (low level) data isoutput from IC805, pin 54.When a WIDE (high level) data is received, Q401 turn off.When a NARROW (low level) data is received, Q401 turn on.Q401 turns on/off with the Wide/Narrow data and theIC401 detector output level is switched to maintain aconstant output level during wide or narrow signals.SPBPFIC602AF Amp IC601 IC605AF PAIC401IF,MIX,DETANTAQUACF401TCXOTUNEQ4X3 multiplyTUNEANT SWBPFMCF1st LocalRF AMPQ404 MIXERQ403 XF401 IF AMPQ402AF VOLX116.8MHz2nd LocalQ401H : WideL : NarrowC409W/NR408R409 CD401IFOQUADIC401FM IF SYSTEM5RAFOUTQ402SPTX: 136 ~ 174MHz (K,M)PLLVCOIF SYSTEMANTTCXOX3 multiply49.95MHzMCFAFAMPMICMICAMPTXAMP RFAMP50.4MHzCF450kHzRX: 185.95 ~ 233.95MHz(K,M)TX/RX: 136 ~ 174MHz (K,M)16.8MHzRFAMPANT SW