16
Test Rig Rebroadcast Device
Possibly one of the easiest ways of set-
ting up a rebroadcast unit for testing, is
to mount the component parts onto a
suitable board.
This cuts down the trailing wires and
allows you to fit the device into various
locations for the purpose of testing.
With a big enough vehicle, it’s even
possible to leave it assembled in this
way.
The black cable shown top left of the
picture is the cross-over cable. The one
supplied by Simoco is red in colour but
this one was made up for the job.
Notice that the speaker leads have been
left un-connected. Speakers can be fit-
ted if the vehicle is to be manned and
the system monitored.
The ‘chocolate-block’ connector bottom
left is used to allow a single power sup-
ply lead to be split to two radios.
The small black box at the bottom of
the diplexer
carries two indicator lights which illumi-
nate when the radio they are connected
to, is receiving a signal. This is a quick
way of telling that the system is operat-
ing. They are powered by the pin 8 con-
nection on the facility connector for
each radio.
This is the practical application of the circuit shown on page 17.
The aerial connects to the diplexer
output here.
The simplest form of On/Off indication is a single LED across pins 4 and 8 on the 147 MHz radio programmed to have pin 8
go low on transmit. If the TWC radio receives a signal then the 147 radio will transmit and the LED will light. Both radios are
thus tested as ‘On’ by a single LED.
To Next Page
Loading...
