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The Modified TMC Radio “Standard” Repeater, alternative suggestions. - The Low Band Uplink
It’s clear how much simpler the low-band uplink channel would make life. The need for a diplexer and aerial switching is completely re-
moved although the vehicle will still require two aerials, one low band and one high band.
This is the option chosen by some of our colleagues in Scotland and there is a lot to be said for it’s use by English and Welsh MRT’s. At the
time this document was produced, no such low band uplink channel is available south of the Border but a number of teams have bought their
own from Ofcom.
SRM9030 fitted with MA-ASIG or DMAP board
TWC
Low Band
Secondary Radio
Primary Radio
Control of rebroadcast is via
the programming in both
radios unless the switch op-
tion is used.
It isn’t necessary to program
a ‘Radio Select’ option as the
secondary radio performs
only one function. You need
only program an ‘Auxiliary’
button to send pin 8 low.
Pin 8
Pin 4
If the primary radio has a button programmed to send the DB-15 pin 8, low
when pressed (Auxiliary) then power is supplied to the secondary radio
placing the system, automatically, into rebroadcast mode
Power Relay
Power is switched to the secondary radio,
only if rebroadcast is required
Connection to the vehicle power supply
Permanent connection to the primary radio
Crossover cable
As in the previous circuit, a dash-mounted switch can be used instead of a
relay, no programming is then required.
Two aerials are again required in this
configuration. One Low Band and one
High Band.
Base operates on the low band
channel and the hill-party re-
main on the TWC
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