Codan 2110 series, Repair Manual

Page: 38 / 164

Brief description
22 Manpack Transceiver 2110 series Repair Guide
Transmit path
Front Panel PCB
Microphone transmit audio appears at the handset connector. It is pre-amplified on the
Front Panel PCB, then passed onto the Audio & Control PCB.
Audio & Control PCB
Pre-amplified audio from the Front Panel PCB passes through the optional encryptor
module (where fitted), the codec, and DSP on the Audio & Control PCB. The processing
utilises a compression algorithm that converts the audio signal to a relatively constant
level. The signal is passed to the RF/IF & Synthesiser PCB.
RF/IF & Synthesiser PCB
The audio is mixed with the local oscillator to produce double sideband. It is filtered by a
2.5 kHz sideband filter centred on 455 kHz so that only the wanted sideband is passed to
the second mixer. It is then mixed with the reference oscillator to produce an IF signal
centred on 45 MHz.
The transmit signal is filtered by a BPF with a bandwidth of 15 kHz, before being passed
to the input of the first mixer.
At the first mixer, the signal mixes with the local oscillator VCO to produce the required
channel frequency. The signal is passed to the PA & Filter PCB.
PA & Filter PCB
On the PA & Filter PCB, the signal passes through the first transmit/receive relay to the
amplifier. Following amplification, it passes through the second transmit/receive relay to
the selected LPF.
The output from the LPF passes via the VSWR DETECTOR circuit to the output
connector. From there it is connected by coaxial cable to the Antenna Tuner PCB.
Antenna Tuner PCB
The signal from the PA & Filter PCB is either directly switched to the 50

antenna
connector (J2) or switched via a set of impedance-matching components to the antenna
stud. Matching components are selected during an iterative tuning process (see
page 24,
Antenna tuning process ).