[aprssig] Multiple TNC's connected to one radio

spam8mybrain spam8mybrain at yahoo.com
Thu Oct 26 15:41:54 EDT 2017

Ah, but what if DireWolf is one of the TNC's he wants to test? :-) It sounds like he wants to compare different TNC's audio processing.
Probably a larger issue here is if the TNC's being compared demand different audio levels. Adjusting the shared audio signal amplitude for best performance on one TNC might ruin the performance of the other TNC (signal lost in the noise or overloading and clipping/distorting in the TNC's analog input). If you really want to do this right, you might want to use an audio distribution amplifier with independently adjustable levels for each output feeding a TNC; incidentally, this would also eliminate all issues of loading down the input source.
Just my $.02.
Andrew, KA2DDO

-------- Original message --------
From: "John D. Hays" <john at hays.org> 
Date: 10/26/17  14:43  (GMT-05:00) 
To: Max Harper <kg4pid at yahoo.com> 
Cc: aprssig <aprssig at tapr.org> 
Subject: Re: [aprssig] Multiple TNC's connected to one radio 

It should work, but I can't vouch for specific TNCs.
Another approach would be to use Direwolf (https://github.com/wb2osz/direwolf) which would give you more sampling opportunites.
On Thu, Oct 26, 2017 at 9:21 AM, Max Harper <kg4pid at yahoo.com> wrote:
  I would like to connect 2 tnc's to one radio. One would be transmitt/recieve and the other recieve only. This would be to test the decoding of a couple different tnc's. Am I likely to run into any problems connecting the speaker jack audio into 2 tnc's? Would the additional load cause me to have to readjust the audio level when I connect/disconnect the second tnc? My thoughts are since the speaker jack audio is low impedance (8 ohm) and the tnc input is much higher (hopefully) is that it will have little to no effect. 
Just thought I'd ask before wasting my time making a cable.

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John D. Hays
Edmonds, WAK7VE


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