Codan Radio Radio Repeater Systems Training Guide - Manual (Page 26)

TRAINING GUIDE | RADIO REPEATER SYSTEM
Chapter 3: Repeater System Equipment Page 18
Codan Radio Communications is a manufacturer of high reliabiltity repeaters and base stations. Codan
receivers and transmitters frequency stability is specifi ed as +/- 1 ppm over the temperature range of
-40 °C to +60 °C (-40 °F to +140 °F), a very wide range and very cold at the lower end. Low audio
distortion in the receivers and transmitters (typically less than 2%) allows the the system designer to link
several sites in a chain to provide extended coverage. Very low current draw on both the synthesized
and crystal controlled repeaters and base stations allows these units to run from solar powered battery
sites. Codan manufactures the repeaters and base stations in a modular confi guration, for ease of
troubleshooting and maintenance.
a) Receiver modules
The receiver squelch circuit also has a form of hysteresis that allows the squelch control to be set at
a level which eliminates noisy signals, but when a signal does open the squelch, the receiver goes to
full sensitivity to allow a fading signal to come through and not be chopped up by the squelch snapping
shut for each momentary fade.
As well as hysteresis squelch, the receiver response time can be modifi ed to suit particular applications.
Some applications require a very fast response to an incoming signal, such as when several repeaters
are linked into a chain. If each receiver was slow in turning on its attached transmitter, the delay over
the length of the chain would be intolerable. The opposite situation is where it is desirable to hold the
transmitter on the air for a brief period although there is no incoming signal. This arrangement allows
two stations to talk back and forth without the repeater dropping out between transmissions.
b) Transmitter modules
The transmitter modules are of an adjustable output power, typically 0.5 to 8 Watts at VHF and UHF.
The transmitters are rated at 100% duty cycle, meaning continuous operation at full output without
degradation over the full temperature range.
An adjustable time-out-timer built into the transmitters can shut down the transmitter after a preset
length of time (adjustable from 1 second to 8 hours). This will stop the transmitter from draining the
batteries when a stuck microphone condition occurs.