Kenwood TK-2160 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 t hen goes t hrough an AF volum e cont rol(VR801), and is routed to an audio pow er amplifier (IC605)w here it is amplified and output to the speaker.Fig. 3 Wide/ Narrow sw itching circuitCIRCUIT DESCRIPTION1. Frequency ConfigurationThe receiver utilizes double conversion. The first IF is 49.95M Hz 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 show s the frequencies.Fig. 1 Frequency configuration1) Front End (RF AM P)The signal coming from the antenna passes through thetransmit/receive sw itching 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 M ixerThe signal from the front end is mixed w ith the first localoscillator signal generated in the PLL circuit by Q403 toproduce a first IF frequency of 49.95 M Hz.The resulting signal passes through the XF401 M CF to cutt he adjacent spurious and provide t he opit im uncharacteristics, 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 syst em IC provides a second m ixer, second localoscillator, limiting amplifier, quadrature detector and RSSI(Received Signal Strength Indicator). The second mixermixes the first IF signal w ith the 50.4M Hz 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 w ith the ceramicdiscriminator (CD401). The demodulated signal is routedto the audio circuit.4) Wide/ Narrow Sw itching CircuitNarrow and Wide settings can be made for each channelby sw itching 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 w ith the Wide/Narrow data and theIC401 detector output level is sw itched to m aintain aconstant output level during w ide or narrow signals.SPBPFIC602AF Am p IC601 IC605AF PAIC401IF,M IX,DETANTAQUACF401TCXOTUNEQ4X3 m ultiplyTUNEANT SWBPFM CF1st LocalRF AM PQ404 M IXERQ403 XF401 IF AM PQ402AF VOLX116.8M Hz2nd LocalQ401H : WideL : NarrowC409W/NR408R409 CD401IFOQUADIC401FM IF SYSTEM5RAFOUTQ402SPTX: 136 ~ 174M Hz (K,M )PLLVCOIF SYSTEMANTTCXOX3 m ultiply49.95M HzM CFAFAM PM ICM ICAM PTXAM P RFAM P50.4M HzCF450kHzRX: 185.95 ~ 233.95M Hz(K,M )TX/RX: 136 ~ 174M Hz (K,M )16.8M HzRFAM PANT SW