[aprssig] Voice Repeater ==> APRS Interface

Corey Shields cshields at indiana.edu
Thu May 8 20:56:58 CDT 2008

Robert Bruninga wrote:
> Yes, and I think it would not take more than about a few dozen
> lines of code to do a rudimentary conversion from DTMF callsign
> to APRS packet and is trivial for someone to add to such
> dedicated micros if the implementer is motivated to do so.

You should see the dtmf logs of a repeater with such functionality (like 
IRLP) sometime..  Unless the repeater is dedicated to aprstt only when 
it comes to dtmf, then how do you differentiate between a good command 
and junk?  At least in our case (IRLP and Echolink on the repeater), 
something so simple as "111" to turn the IRLP node on and then 4 digits 
to dial a node invites a log full of random DTMF attempts and rejected 

With varying numbers in callsign digits you can't expect a set string 
length, and this becomes more complex when you consider repeating 
characters (take an old club I once belonged to, W9UUU..  on the keypad 
someone might try 99999888888..  which could also be W9VV, W9TVU, XY8TT, 
etc..)  As your doc states, the proper way to do this would be 
9A999988A88A88, but I bring this up to point out that all it takes is 
one goof on the dtmf pad to screw it up.  How important is it that the 
data be correct?  Goes back to the issue of a log full of people who 
can't even get an IRLP connection up with DTMF, something that takes far 
less in my opinion.

So while it would take just a few dozen lines of code to create a 
callsign out of a DTMF string, making sure you get what the user 
intended (and differentiating that from IRLP and Echolink commands) 
would be a bit of a PITA.

Again, I love the idea of allowing 100% of the hams to show up on APRS.  
Maybe go for the low-hanging fruit and make a web form that allows the 
majority of them sitting behind a rig at home to just ID themselves to 

And as you pointed out, the hobby is one of experimentation and coming 
up with new things.  Maybe if you got this to work as-is now, idea 2.0 
would solve some of these issues..  Good luck.

-Corey  KB9JHU

Corey Shields
High Performance Systems, Indiana University - UITS

More information about the aprssig mailing list