[aprssig] Xastir Internet->RF configuration

Tim Cunningham tim_cunningham at charter.net
Tue Apr 7 16:03:12 EDT 2009

Just for clarification. TXDelay is a parameter that has an impact on both 
ends of the link. It is not simply something that is set to see how fast 
your radio can lock on frequency and come up to power. There are 
ramifications on the receive end as well.

While you may be able to set TXDelay less than 100ms, it does not mean 
everybody can decode it. For users who still use a squelch circuit ahead of 
their audio tap, you must allow enough time for the squelch to open the 
audio path before data can pass for decoding.

The real question may be how slow is the slowest squelch circuit on your 


Tim - N8DEU
Decatur, Alabama

----- Original Message ----- 
From: "Keith VE7GDH" <ve7gdh at rac.ca>
To: "TAPR APRS Mailing List" <aprssig at tapr.org>
Sent: Tuesday, April 07, 2009 1:56 PM
Subject: Re: [aprssig] Xastir Internet->RF configuration

> Curt WE7U wrote...
>> I'm using the "Serial KISS TNC" interface and have "40" entered for 
>> TXDelay (400 ms), but for my KISS TNC it doesn't matter as it's set with 
>> a pot on the TNC (TNC-X).
>> I usually set it between 25 and 40, depending on the radio.  With
>> different TNC's than this one of course.
> I realize you are using the TNC-X where the TXDelay is set with a pot, but 
> for anyone using another TNC where it is set in software, 250 to 400 ms is 
> usually much longer than needed. I have reliably used less than 100 ms, 
> regularly use 100 ms and suggest about 125-150 ms for someone that doesn't 
> want to take the time to see if shorter TXDelay can be used. Yes, if it's 
> too short, no-one will be able to decode your tones, but set too long, and 
> it uses up valuable bandwidth.
> 73 es cul - Keith VE7GDH
> --
> "I may be lost, but I know exactly where I am!"
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