[aprssig] digipeater query

w0ep w0ep at frii.com
Fri Feb 3 23:26:08 EST 2006

I'm running a little digipeater here and recently it decided to become
very deaf.    I've been using an old Icom IC-2200H which is somewhat
crippled in the transmit output department (I replaced the T/R PIN
diode with a smaller wattage unit some time ago).  I have soundmodem
software running on a RedHat linux system, with javAPRServer doing the
digi and igate job.

I built myself a transformer coupled interface a few months ago,
and it seemed to me that the old digi was hearing things I was
missing before that.  

But like I said, it recently went almost completely deaf.

Using the soundmodemconfig tool, I can see a spectrum of the
input and set the level.  When connected to the audio out of the
IC-2200H  I see good level but nothing gets decoded.  When I connect
to the headphone jack of a scanner, things get decoded right again.

I'm thinking either the frequency of this 2200H has drifted, or
the audio out is distorted enough to keep the decode from working

One of the problems may be that the new transformer-coupled box is
making me drive the audio out from the radio quite a bit harder
than I would like.  I think I'm going to check out the 1:1 audio
transformers from RadioShack and see if they are a little easier to
drive.  (My transformers came from old modem cards.)  I wonder
if maybe I've worn out something in the audio output circuit by
driving it too hard.

I'm also going to see if a nearby friend can put the radio on his
service monitor and see what the frequency accuracy looks like.

Any comments?


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