[aprssig] APRStt Callsign and Checksum
bruninga at usna.edu
Tue May 12 14:00:05 EDT 2009
> Thanks for the info. I wasn't it reading
> right the first time. I have a further question though.
> The total for my callsign is 101 like yours
> so my checksum is 1. Where do we get 1 from 101?
>> ... You just add up all the keys in the callsign,
>> and keep only the units digit of the sum.
We will make it clearer in the docs when we get the chance.
> On Tue, May 12, 2009 at 10:14, Robert Bruninga
> <bruninga at usna.edu> wrote:
> It would be nice if someone would write an APRStt
> GENERATOR routine for everyone to use. They could just
> their callsign, and out comes the DTMF keys to put into
> This automatically generates the 2-key conversion and
> An ON_LINE generator would even be better!
> > I have a question about the APRStt checksum.
> > What is it and what is it for?
> Since the callsign is only entered once into a DTMF
> easy transmission, we thought it should have a checksum
> greatly minimize the chance for errors. You just add up
> keys in the callsign, and keep only the units digit of
> That then is the checksum digit. If APRStt reecives a
> string and the checksum does not match, then there is an
> The APRStt DTMF string for callsigns is:
> Where V is a user selected overlay byte (or two byte
> Where K is the checksum (treat ABCD keys as HEX)
> Where each letter of the callsign is encoded using the
> text system
> See www.aprs.org/aprstt/aprstt-user.txt
> Bob, WB4aPR
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