Kenwood TK-7360 Service Manual

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TK-7360/7360H/7360H ( V )142-4. Wide/Narrow Switching CircuitThe Wide port (pin 99) and Narrow port (pin 98) of theMCU is used to switch between ceramic filters. When theWide port is high, the ceramic filter switch diodes (D500,D501) cause CF500 to turn on to receive a Wide signal.When the Narrow port is high, the ceramic filter switchdiodes (D500, D501) cause CF501 to turn on to receive aNarrow signal.NarrowIC704pin98IF_IN MIX_OIC500FM System ICCF501(Narrow)CF500(Wide)R506R508R507R505D500 D501WideIC704pin99Fig. 3 Wide/Narrow switching circuit2-5. AF Signal SystemThe detection signal from the FM IC (IC500) goes to thebaseband IC (IC702) DISC input (pin 16) for characterizingthe signal.The AF signal output from IC702 is input to the audiopower amplifier (IC706). The AF signal from IC706 switchesbetween the internal speaker and the speaker jack (J701)output.BasebandICIC702AF PAIC706 SPFM ICIC500Fig. 4 AF signal system2-6. Squelch CircuitThe detection output from the FM IC (IC500), a voltageis applied to the MCU (IC704). The MCU controls squelchaccording to the voltage (SQIN) level.The signal from the RSSI pin of IC500 is monitored.The electric field strength of the receive signal can beknown before the SQIN voltage is input to the MCU, andthe scan stop speed is improved.FIL_OUTRSSIQ505 D502Noise DETIC704MCUIC500FM ICNoiseAMPSQINRSSIFig. 5 Squelch circuit3. Transmitter System3-1. OutlineThe transmitter circuit produces and amplifies the de-sired frequency directly. It FM-modulates the carrier signalby means of a varicap diode.3-2. Power Amplifier CircuitThe transmit output signal from the VCO passes throughthe transmission/reception selection diode (D17) and ampli-fied by Q300. The amplified signal goes to the RF powermodule (IC300) through a low-pass filter. The lowpass filterremoves unwanted high-frequency harmonic components,and the resulting signal goes through the antenna terminal.3-3. APC CircuitThe automatic transmission power control (APC) circuitdetects part of a final amplifi er output with a coupler circuitand applies a voltage to IC301. IC301 compares the APCcontrol voltage (PC) generated by the baseband IC (IC702)and DC amplifier (IC501) with the detection output voltage.IC301 generates the voltage to control IC300 and stabilizestransmission output.The APC circuit is configured to protect over current ofQ300 and IC300 due to fluctuations of the load at the anten-na end and to stabilize transmission output at voltage andtemperature variations.DRIVEAMPRF POWERmoduleQ300 IC300DCAMPIC501ANTSWD303,D304LPFANTIC301APCcontrolCouplercircuitD17APCCIC702pin32Fig. 7 APC circuitFig. 6 Transmitter systemANTIC701MICMICAMPQ712SWMCUQ6TXVCOQ12BUFFAMPQ13RFAMPDRIVEAMPQ300 IC300RF POWERmodulePLL ICTCXO19.2MHzMIC keyinputIC702BasebandICIC704 X1 IC2RFAMPQ3CIRCUIT DESCRIPTION