[aprssig] APRStt Callsign and Checksum
Matt Murphy matt.kc8bew at gmail.comWed May 13 00:10:30 UTC 2009
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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 > > > > > > > > > > > > -------------- next part -------------- An HTML attachment was scrubbed... URL: <http://www.tapr.org/pipermail/aprssig/attachments/20090512/ee853e1b/attachment.htm>
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