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[aprssig] APRStt gateway SITREP

F5SMZ Jean-Philippe f5smz at wanadoo.fr
Thu Oct 2 16:24:13 UTC 2008


Hi all APRStt fans, (and addicted keypad users)

here is the situation today:

1) extensive testing, development and debugging is ongoing here with the team (F4ASB: developer; F4ARO: "chief" beta tester and debug and other local contributors from our clubstation F8KHP in JN38EE)
2) concerning the DTMF keypad layout we made a choice today in order to go forward and speed up things, by keeping in mind that the callsign sequences (A) MUST:
* be stored in a DTMF memory
* will not exceed in ANY cases 16 characters (so the only way to guaranty this is using the deterministic 2 digits manner "à la " Echolink).
* the ITU 161 DTMF keyboard layout will be used (as GSM mobile phones and Yaesu VX-8R)
* will be usable in ANY country
3) ABREVIATED CALLSIGNS (suffix) must be as short as possible to be reused for POS, MSG and QRY sequences.(3 digits max)
4) the APRStt gateway IS a "self-learning" piece of software ... will explain below
5) Initial release is only IMPLEMENTING "A" sequences: callsigns check-in/out.

>From a software development point of view I need to deliver something as an UI-view add-on (initially) that works in EVERY country whatever callsign prefix characters and length rules are. This is ONLY for "A" sequences (callsign sequences). In this way, ANY callsign with 6 characters will be DTMF encoded with a maximum of 12 digits. We still need to agree if "A" become "C" or not.

As Bob mentionned yesterday, ABREVIATED callsigns will focus on SUFFIX only; this way, we are able to build these shortcuts with only 3 digits following a given algorithm. Ex: my callsign F5SMZ (suffix SMZ) is computed by the gateway "478" and sent back in vocal synth the first time I check-in; I can reuse it in ANY DTMF sequence later (even for further check-in/out) once I've sent the initial FULL sequence corresponding to my callsign. The gateway store it in the database and will always recognize my DTMF sequences in the future.
This way, the APRStt gateway is self-learning; e.g as more and more APRStt stations check in, the gateway update his internal database AND compute the related ABREVIATED callsign . The 3 digits ABBREVIATED callsign algorithm maintain a very low probability to generate dupes; remember, APRStt is a LOCAL application. Following this procedure we can add ANY callsign (especially here in Europe where countries are "small", and I can meet lots of stations from DL, LX and HB9 every day on a repeater as well.

Hope we go in the right way; in case not, feel free to give your feedback, proposals and ideas.


 73 de F5SMZ, Jean-philippe
f5smz at wanadoo.fr
Skype: f5smz88
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