Kenwood TK-7360 Service Manual

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TK-7360/7360H/7360H ( V )131. Frequency ConfigurationThe receiver utilizes double conversion. The first IF is38.85MHz and the second IF is 450kHz. The first local oscil-lator signal is supplied from the PLL circuit.The PLL circuit in the transmitter generates the neces-sary frequencies. Figure 1 shows the frequencies.ANTSW RFAMP1stMIXAFPATCXOMICAMPX2multiplyRFAMPPOWERAMPCF 450kHzMCF38.85MHzIF SYSTEMPLL/VCO19.2MHz38.4MHzANTRXTXSPMICFig. 1 Frequency configuration2. Receiver SystemThe receiver is a double conversion superheterodyne.The frequency confi guration is shown in Figure 1.2-1. Front-end RF AmplifierAn incoming signal from the antenna is applied to an RFamplifier (Q511) after passing through the transmit/receiveswitch circuit (D303, D304, D307 and D308) and bandpassfi lter (L518, L519 and varactor diodes: D506, D507).After the signal is amplified (Q511), the signal is filteredby the bandpass (L513 and varactor diodes: D504, D505) toeliminate unwanted signals before it is passed to the firstmixer.The voltage of these diodes are controlled by trackingthe MCU (IC704) center frequency of the bandpass filter.(See Figure 2)2-2. First MixerThe signal from the RF amplifier is heterodyned with thefirst local oscillator signal from the PLL frequency synthe-sizer circuit at the fi rst mixer (Q507) to create a 38.85MHzfirst intermediate frequency (1st IF) signal. The first IF signalis then fed through one pair of monolithic crystal filters (MCF:XF500) to further remove spurious signals.Item RatingNominal center frequency 38.85MHzPass bandwidth ±6.0kHz or more at 3dB40dB stop bandwidth ±25.0kHz or lessRipple 1.0dB or lessInsertion loss 4.0dB or lessGuaranteed attenuation 75dB (–900kHz); 50dB (+900kHz)Spurious: 40dB or more within fo±1MHzTerminal impedance 610Ω// 3.0pF// Coupling Cap 13.0pFTable 1 Crystal filter (L71-0659-05): XF5002-3. IF Amplifier CircuitThe first IF signal is amplified by Q504, and enters IC500(FM processing IC). The signal is heterodyned again witha second local oscillator signal within IC500 to create a450kHz second IF signal. The second IF signal is then fedthrough a 450kHz ceramic filter (Wide: CF500, Narrow:CF501) to further eliminate unwanted signals before it isamplified and demodulated by the quadrature detector withthe ceramic discriminator (CD500).Item RatingNominal center frequency 450kHz6dB bandwidth ±6.0kHz or more50dB bandwidth ±12.5kHz or lessRipple 2.0dB or lessInsertion loss 6.0dB or lessGuaranteed attenuation 35.0dB or more within fo±100kHzTerminal impedance 2.0kΩTable 2 Ceramic filter (L72-0993-05): CF500Item RatingNominal center frequency 450kHz6dB bandwidth ±4.5kHz or more50dB bandwidth ±10.0kHz or lessRipple 2.0dB or lessInsertion loss 6.0dB or lessGuaranteed attenuation 60.0dB or more within fo±100kHzTerminal impedance 2.0kΩTable 3 Ceramic filter (L72-0999-05): CF501CIRCUIT DESCRIPTIONFig. 2 Receiver SystemANTL518,L519D506,D507BPFQ511RF AMP Q504IF AMPQ507MIX XF500MCFD303,D304D307,D308ANTSWIC501DC OP AMPQ500DoublerX1TCXOIC500FM system IC IC702Baseband IC1st localOSC (VCO/PLL)CF500 (Wide)CF501 (Narrow)TVCD500TVC &APCCL513D504,D505BPF