Codan 2110 series, Руководство по ремонту, Страница: 65 / 164

Functional description of PCBs
Manpack Transceiver 2110 series Repair Guide 33
RF/IF & Synthesiser PCB
The RF/IF & Synthesiser PCB performs the following functions:
• provides a low-level RF signal at the channel frequency, modulated with the Tx
audio
• switches the Tx/Rx paths
• modulates and demodulates the audio signal
• mixes the 455 kHz IF, band-pass filtering (Z201), and amplification
• mixes the 45 MHz IF, band-pass filtering (Z101, Z102), and amplification
• limits noise
• provides a REF OSC for the DDS, PLL and LO2 circuits
• generates 45.25 to 75 MHz references for the 1st mixer via a VCO and PLL
• provides switchable RF pre-amplification of the incoming Rx signal
• switches between USB and LSB
• provides the RF source for a tune signal
• provides AGC control
• interprets commands from the Audio & Control PCB
The RF/IF & Synthesiser PCB contains:
• Tx mixers
• Rx mixers
• a noise limiter
• a Tx modulator
• an Rx demodulator
• a PLL
• a DDS
• a VCO
• a PIC microcontroller
• a Crystal Oven PCB
For details on the RF/IF & Synthesiser PCB,
Codan part number See...
08-06039-001 Table 8 on page 34 and
Figure 11 on page 30