Kenwood TKR-850 Service Manual

Also see for TKR-850: Brochure & specs Function reference Instruction manual Instruction manual Programming reference

TKR-850111. OutlineThe TKR-850 is a UHF/FM repeater designed to operate inthe frequency range of 400 to 512MHz.The unit consists of receiver, transmitter, phase-lockedloop (PLL) frequency synthesizer, and control circuits.2. Receiver CircuitThe receiver is double conversion super-heterodyne, de-signed to operate in the frequency range of 440 to 470MHz(E), 450 to 480MHz (K), 480 to 512MHz (K2) or 400 to 430MHz (K3).The receiver circuit located in TX-RX unit (X57-696 A/2)consists of the following : 2-1 front-end circuit, 2-2 first mixer,2-3 IF amplifier circuit, 2-4 audio amplifier circuit, and 2-5squelch circuit.2-1. Front-end CircuitThe front-end circuit consists of BPF L2, RF amplifier Q1,and BPF L4/L5. The helical BPF covers frequency ranges 440to 470MHz (E), 450 to 480MHz (K), 480 to 512MHz (K2) or400 to 430MHz (K3), with a passband of 5.0MHz.The BPF L4/L5 attenuates the unwanted signals, andsends only the necessary signal to the first mixer DBM A1.2-2. First MixerThe signal from the BPF is heterodyned with the first localoscillator signal from the PLL frequency synthesizer circuit atthe first mixer DBM (A1) to become a 44.85MHz first inter-mediate frequency (IF) signal. The first IF signal is fedthrough two monolithic crystal filters (XF2; Wide, XF1; Nar-row) to further remove spurious signals.W/NSQLDETTX-RX unit (X57 A/2): TX-RXSWSWW/NW/NMCF (Narrow)XF1MCF (Wide)XF2RSSIQUDW/NSWDETVCO AVCO BRX VCOA3 (X58-480)RX ANTBPFL2RF AMPQ1BPFL4,L51st MIXDBM A1IF AMPQ8IF AMPQ9IF AMPQ10LPFIF AMPQ244.85MHzD1D2IF AMPQ3FM SYSTEM ICIC9SWSWNOISE DETD5NOISE AMPQ7D3D4X144.395MHzCF1 (Wide)CF2 (Narrow)Q4f RX –44.85MHzDEI DEORDCODECRARXI RXODACAMPIC608AMPIC619 (B/2)LPFIC619 (A/2)AINR AOUTRCPUIC614IC604IC615SWIC622MUTEQ606AMSPMAFAMPINT SPIC629RSSIASQTX-RX unit (X57 B/2): Control455kHz44.850MHzIC621 Q605INVFig. 1 Receiver circuitCIRCUIT DESCRIPTION