[aprssig] ARISS digi

[Stephen H. Smith]

On 2/19/2011 11:22 AM, Ted Antanaitis wrote:
> A friend was trying to digi via the ISS and observed his packets on the APRS-IS:
>
> 2011-02-19 05:09:28 UTC: AD7FC>T6SUVX,WIDE1*,WIDE2-1,qAo,AC7KW:`0;^l+c[/>=
> 2011-02-19 05:09:43 UTC: AD7FC>T6SUVX,WIDE1*,WIDE2-1,qAR,N0AN:`0;^l>[/>=
> And
> 2011-02-19 08:20:41 UTC: AD7FC-9>T6SUVY,WIDE2-1,qAR,WA6LIE-3:'0;`l<0x1c>-/]
>
> I do not recognize 'T6SUVX', does anyone else have a clue as to what that is?
>
> If this indeed was digi'ed thru the ISS why wasn't it listed on the 
> www.ariss.net list?
>
> TNX in advance
>
> Ted WA7ZZB
>


This is a highly-compressed Mic-E format position report.   To make the packet 
absolutely as short as possible, part of the latitude information is encoded 
and placed in the destination call area.  The "gibberish at the end of the 
string is also part of the position data.  If the AD7FC-9 had been moving, you 
would have seen this "call sign" (and the tail end of the string) constantly 
changing.

Kenwood radios and TinyTracks generate this kind of compressed position report 
format.   Mic-E  (Mike Encoder) format was originally developed years ago for 
use on shared voice/APRS channels.  The idea was to send the shortest possible 
packet at the end of voice transmissions when you unkeyed the mic.  The 
original TAPR "Mic Encoder" was a box you inserted between your mic and the 
radio's mic jack.  (A complete Mic-E position report is only a 1/3rd to 1/2 
second squawk.)    Mic-E results in a position string about 1/3rd as long as 
standard APRS format and about ONE-TENTH as long as sending raw NMEA GPS data.

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Stephen H. Smith    wa8lmf (at) aol.com
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