[aprssig] Putting a digi on a 2m repeater

Keith VE7GDH ve7gdh at rac.ca
Thu Mar 10 15:33:51 EST 2011

 Kent KQ4KK wrote...

> We have a 2m repeater on 147.315+ that we have been told we could
> add a digi on 144.39. Does someone have some words of wisdom, photos,
> web pages, diagrams on how to do this?

At least 144,390 is the opposite end of the band from 147.315, and more
importantly, from 147.915. If it's "easy access" you could fire up a 144.390
transmitter right at the digi site to see if there was much desensing on the
voice repeater. It probably wouldn't hurt to add a cavity or two on the coax
to the APRS radio. You could set one up as a bandpass filter on 144.390 and
the other and a band reject filter on 147.315 to minimize desensing the APRS
receiver. Are you going with separate antennas, or thinking of something like
a circulator so you could use just one antenna?

The other thing to consider is if the repeater site is suitable to have a digi...
i.e. it isn't surrounded by hilltops with digis on them, or if it was in a very
high location, if it was too high. Where there is very low APRS usage, or
not many digis, a high digi can be a good thing. If it is near several large
population centres, a high digi might be undesirable. If it goes ahead, don't
forget to set up a repeater object in the digi to advertise the voice repeater!

73 es cul - Keith VE7GDH
"I may be lost, but I know exactly where I am!"

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