[aprssig] APRStt Callsign and Checksum
Matt Murphy
matt.kc8bew at gmail.com
Tue May 12 19:10:30 CDT 2009
I didn't understand what the "units digit" but I did some more research and
I now understand it.
(I didn't remember that from math class) The units being the ones place.
Got it now.
Thanks for the help.
73,
Matt Murphy, kc8bew
http://mcares.kc8bew.net
Muskingum Co. ARES EC
On Tue, May 12, 2009 at 14:00, Robert Bruninga <bruninga at usna.edu> wrote:
> > 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.
>
> Thanks
> Bob
>
> > 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
> CALLSIGN
> > GENERATOR routine for everyone to use. They could just
> type in
> > their callsign, and out comes the DTMF keys to put into
> memory.
> > This automatically generates the 2-key conversion and
> checksum.
> > 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
> memory for
> > easy transmission, we thought it should have a checksum
> to
> > greatly minimize the chance for errors. You just add up
> all the
> > keys in the callsign, and keep only the units digit of
> the sum.
> > That then is the checksum digit. If APRStt reecives a
> DTMF
> > string and the checksum does not match, then there is an
> error.
> >
> > The APRStt DTMF string for callsigns is:
> >
> > AcccccccccccVK#
> >
> > Where V is a user selected overlay byte (or two byte
> letter)
> > Where K is the checksum (treat ABCD keys as HEX)
> > Where each letter of the callsign is encoded using the
> 2-key
> > text system
> >
> > See www.aprs.org/aprstt/aprstt-user.txt
> >
> > Bob, WB4aPR
> >
> >
> >
> >
> >
>
>
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