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[aprssig] Symbol Protocol Help

Robert Bruninga bruninga at usna.edu
Tue Apr 22 14:02:04 UTC 2008


>>> What I don't get is the xyz equivalent.  
>>> Why is the xyz equivalent of "/!", "BB"? 
>> 
>> Because it is the 2nd character in the "Bth" series.
> 
> Nice!  That makes sense to me (finally). :)
> ...is it accurate to say that in GPS/SYM/SPCxyz,
> xy is a 2-dimension array (where xy [together] defines
> a symbol) and z is a literal ASCII overlay character?

Yes. All symbols are in a two dimensional #$ array consisting of
the # TALBE character and the $ SYMBOL character which I usually
refer to as "/$" in my docs.  But for GPSxyz which has to go in
an AX.25 TNC TOCALL these bytes can only be uppercase letters
and numerals.  So we re-defined the characters for x and y, and
then added z to carry the overlay character if any...

> I notice... the following "series" have been defined:
> 
> Primary/Secondary
> B/O
> P/A
> M/N
> H/D
> L/S
> J/Q
> 
> Why was "B" the first series of the primary table,
> rather than "A" (which is the third series of the
> secondary table?

Actually P was the first Primary table and then A when we added
the alternates.  Then we added L for lower case and S for
secondary.  Those are the biggest tables.  Then the B table and
the "O" other table... And so on..
 
> These are 12 "series" defined.  What would keep more
> from being defined and used (other than the fact the
> the symbol set doesn't exist in the clients)?

Because they are only an artificial nomenclature for the
original #$ array.  Which can only be 3420 combinations.

Bob, WB4APR





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