Kenwood TH-D72A Service Manual

Also see for TH-D72A: Instruction manual User manual Instruction manual Instruction manual Instruction manual

Contents

TH-D72A/D72E53. Receiver System3-1. VHF receiver circuit■ A band VHF receiver circuitThe reception signal from the antenna passes through afilter circuit and goes to the RF amplifier (Q11). The ampli-fied signal then enters the band-pass filter. After the signalpasses through the band-pass filter, it is amplified by a sec-ond RF amplifier (Q7) and passed through the band-pass fi l-ter before entering the mixer (Q2). The signal converted bythe first-local oscillator (Upper heterodyne) to generate thefirst IF signal (49.950MHz) passes through the MCF (XF351),is amplified by the IF amplifier (Q358) and then enters theFM IC (IC353). The signal is converted to the second IFsignal (455kHz) by the second-local oscillator (Upper hetero-dyne) which generated three times to 50.400MHz and isdetected to generate an audio signal.■ B band VHF receiver circuitThe reception signal from the antenna passes through afi lter circuit and goes to the RF amplifier (Q13). The ampli-fi ed signal then enters the band-pass filter. After the signalpasses through the band-pass filter, it is amplified by a sec-ond RF amplifier (Q8) and passed through the band-pass fil-ter before entering the mixer (Q4). The signal converted bythe first-local oscillator (Upper heterodyne) to generate thefirst IF signal (45.050MHz) passes through the MCF (XF352),is amplified by the IF amplifier (Q359) and then enters theFM IC (IC354). The signal is converted to the second IFsignal (455kHz) by the second-local oscillator (Upper hetero-dyne) and is detected to generate an audio signal.■ VHF accompanying circuitEach band-pass filter is tuned to a target frequencythrough the variable-capacitance Diode by the tuning volt-age output from E-Volume (IC721) controlled with the MainMCU (IC737).Figure 2-1 VHF receiver circuitA bandAFB bandAFAGCIC352D352SWSWSWD351AMDETIC351 Q352 Q354 Q356455kHzCF351Q353Q355Q359 XF35245.050MHzQ41st LocalB bandD26,D27D14,D15 Q8 D44,D45D35,D36Q13Q16 AIPSWAIPSWQ15IC611SubMCUIC721E-VolumeIC737MainMCUVHFBPFQ11D42,D43D32,D33Q7D24,D25D12,D13Q2XF35149.950MHzQ3581st LocalA band2nd Local50.400MHz2nd Local45.505MHzCF352450kHzIC353A band demodulatorIC354B band demodulatorDETDETCIRCUIT DESCRIPTION