[aprssig] DTMF encoding

F5SMZ Jean-Philippe f5smz at wanadoo.fr
Tue Sep 30 16:38:27 CDT 2008

Hi all,
following the various posts today, here is the my proposal/conclusion:

1) First, it appears that we need to stay below 17 digits (e.g most of TRX have a 16 digits memory bank limit)
2) We need a standard DTMF keyboard layout (GSM/Yaesu keyboard is fine; or at least more "standard")

Here we go:

Let's assume we use an encoding system "a la " Echolink; it will lead us to a maximum of 12 digits for a 6 character callsign.
Example: F5SMZ = 3350746194

We need a checksum after that: 3350746194K
and a "D" to terminate the sequence: 3350746194KD

Now suppose we skip the ## preamble and just include the leading A: A3350746194KD
We have now a 13 digits sequence; in case we have a 6 characters callsign, we reach 15 digits, which is still below the 16 digits memero bank limit of most TRX.

This let us also run the B, C and Q APRStt sequences in the future.

Hope it's help.

jean-philippe F5SMZ
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