RCA BR200DV, Service Manual

Page: 22 / 79

BR200DV/BR300DV
Service Manual
22
Chapter 5 Circuit Description
5.1 Frequency configuration
The reference frequency of frequency synthesizer is provided by 16.8MHz crystal oscillator X1 TCXO.
The receiver adopts quadric mixing mode. The first IF is 49.95MHz, and the second IF is 450kHz. The
first local oscillation signal of the receiver is produced by frequency synthesizer and the second local
oscillation signal selects the 4
rd
harmonics of 16.8MHz of crystal oscillator X1 TCXO. The signal of
transmitter is produced by frequency synthesizer directly.
Figure 1 Frequency configuration
5.2 Receiver
（
Rx
）
The receiver is double conversion superheterodyne,designed to operate in the frequency range of
136 to 174MHz,The frequency configuration in Fig 1
Figure 2 Receiver section configuration
Front End of Receiver
Signals from the antenna are filtered by BPF via RX/TX switch (D101 D102 and D103). After being
filtered out the useless out-of-band signals, the signals are amplified by LNA consisting of Q203 and
external components.