Kenwood TK-8150 Service Manual

Also see for TK-8150: Specifications Specifications Instruction manual Instruction manual Service manual

Contents

TK-815012CIRCUIT DESCRIPTION1. OutlineThe TK-8150 is a UHF/FM transceiver designed to operatein the frequency range of 450 to 500MHz. Transmission out-put power is 45 watts. The maximum channel capacity is128.The unit consists of receiver, transmitter, phase-lockedloop (PLL) frequency synthesizer, and control circuits.2. Receiver CircuitThe receiver is double conversion superheterodyne, de-signed to operate in the frequency range of 450MHz to500MHz.The receiver circuit consists of the following : 2-1 front-end circuit, 2-2 first mixer, 2-3 IF amplifier circuit, 2-4 audioamplifier circuit, and 2-5 squelch circuit.2-1. Front-end CircuitThe front-end circuit consists of former BPF (D211 and212), RF amplifier Q214, and latter BPF (D207, D208, D209and D210). The BPF covers frequency ranges 450 to500MHz.The latter BPF (D207, D208, D209 and D210) attenuatesthe unwanted signals, and sends only the necessary signal tothe first mixer.2-2. First MixerThe signal from the BPF is heterodyned with the first localoscillator signal from the PLL frequency synthesizer circuit atthe first mixer DBM (Q210, Q211, Q212 and Q213) to be-come a 73.05MHz first intermediate frequency (IF) signal.The first IF signal is fed through two monolithic crystal filters(XF201; Wide, XF202; Narrow) to further remove spurioussignals.2-3. IF AmplifierThe first IF signal is amplified by Q207 and Q206, and thenenters IC201 (FM system IC). The signal is heterodynedagain with a second local oscillator signal (73.505MHz) within IC201 to become a 455kHz second IF signal. The secondIF signal is fed through a 455kHz ceramic filters (CF201 andCF203; Wide, CF202 and CF204; Narrow) to further eliminateunwanted signal, and the quadrature detection circuit FM-de-tects the signal to produce a base-band signal and output itfrom pin 9.SWW/NMCF (Narrow)XF202MCF (Wide)XF201 IF AMPQ207D206D205IF AMPQ20673.05MHzSWW/NSWW/NCF202,204(Narrow)CF201,203(Wide)D204D203455kHzDETNOISE DETD202SWW/NQ205SWW/NSW SWAMP73.05MHz1st MIX DBMQ210~213BPFD207~210RF AMPQ214 BPFD211,212NOISEAMPQ204QUDFM SYSTEM IC : IC201RSSIDETSQLX20173.505MHzQ508Buff AMPQ513,515RF AMPQ208RF AMPQ209LPFfRX–73.05MHzRX VCOAMPIC712 (A/2)AINR AOUTRCODECIC713CPUIC701IC714DEOLPFIC716 (A/2) IC724 IC722MUTEQ711 IC717AFAMPIC720RXO AFORXIDACIC718ASQRSSIINT. SPRX ANTTX-RX UNIT (X57-658)Fig. 1 Receiver circuit