[aprssig] Symbol Protocol Help

Robert Bruninga bruninga at usna.edu
Wed Apr 23 15:07:34 EDT 2008

> 12 "series"
> (Primary/Alternate, Lowercase/Secondary, B????/O????,
> M????/N????, H????/D????, J????/Q????)

Thoser are arbitrary nomenclature.  APRS symbol field consists
only of two bytes.  The second byte is one of 95 ASCII symbols.
The first byte is either "/", "\" or the overlay characters 0-9
and A-Z.

> Also, what are the valid characters for the z-value of
> xyz?

That is just another way of expressing the above TWO byte
system.  The difference being is that "XYZ" cannot contain ANY
ascii bytes except for A-Z and 0-9.  SO we had to make arbitrary
pointers using that limited set to point to the original set.

> Are there any APRS protocol restrictions (without
> regard as to the existing client's ability to actually
> decode it) to using GPS/SYM/SPCxyz in an APRS
> datagram? (i.e.-WB4APR>SYMLPR,WIDE2-1,...)

I wonder how many do.

AND that ONLY WORKS if the packet contains a RAW NMEA GPS data.
I'm not sure that it applies to any other packet.  Youd have to
look at the spec.


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