[aprssig] Mic-E and HTs

Ian ZL1VFO zl1vfo at yahoo.co.uk
Wed Dec 14 04:37:22 CST 2005

> From: <scott at opentrac.org>
> Subject: RE: [aprssig] Mic-E and HTs

>> it's (TT3) data burst on the end of the over. (Mic-E PTT action, as
>> opposed to a Mic-E compressed packet.)
>> D6 is there to stop it retriggering itself.

> Right, but with most HTs there's going to be no separation between PTT IN
> and PTT OUT - you still have to get the audio from the mic to the HT, and
> that's the same line as the PTT, unless it's a Kenwood or something with a
> separate PTT signal.

> Scott
> N1VG

Right, I see your point now.

In that case, if I were to hook up an external mic/speaker to a
handheld radio via a TinyTrak3, then I'd join the external mic signal
wire to the PTT IN, and use the AUDIO OUT instead of the PTT OUT.

I fugure that there may be a small amount of mic audio loss as the mic
signal travels though D6 and R8 of the TinyTrak3, but it should still
work. If some radios are particularly sensitive about the amount of
resistance in series with the electret mic, then R8 could be lowered a
bit in value, although if lowered too much, the packet audio level
would drop too far as well.

And if I used my Handheld with my Opentracker, the same mic audio path
would be via it's D2 and R3.

I'll have to find some suitable connectors and try the idea out on my


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