Kenwood TKR-740 Service Manual page 32

TKR-740
4.Receiver Unit
The receiver unit (X55-305) consists of the following circuits:
(1) front-end circuit, (2) narrow IF circuit, (3) w ide IF circuit, (4)
receiver main PLL circuit, (5) receiver DDS circuit, (6) baseband
circuit, and (7) other circuits.
4.1 Front-end circuit
The front-end circuit consists of BPF L3, RF amplifier IC17,
BPF L16, mixer DBM A1, and IF sw itch D10. The helical BPF
covers frequency ranges 158.000 to 174.000 M Hz, w ith a
passband of 3.0 M Hz.
BPF L16 at t enuat es t he unw ant ed out -of -band RF
components produced by RF amplifier IC17 and sends only
the desired signal to mixer DBM A1. M ixer DBM A1 mixes
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CIRCUIT DESCRIPTION
the first local oscillator signal generated by the first local crystal
oscillator w ith the receive signal coming from the helical BPF
L16 to produce the first IF signal (44.85M Hz). The first IF
signal is fed to the narrow IF or w ide IF circuit (depending on
programming) by sw itch D10.
Fig.14 Front-end circuit