[aprssig] Short paths in APRS packets

Greg Clark K7RKT at bigredbee.com
Tue Oct 27 11:46:24 EDT 2009

I have two questions regarding building up AX.25 packets.

1) If the "path" fields are shorter than 7 characters, what do they
get padded with. Spaces?  Nulls?  Most "common" paths don't have this
problem, since WIDE3-3 is seven characters.  I'm trying to configure
my tracker for use with the ISS using the paths ARISS and SGATE, and
I'm not sure what to put in the two remaining bytes when I build the
packets.  I'm asuming this field is fixed in length at 7 characters.

2) What about the '-' in the path WIDE3-3, is it really a 'dash' in
the packet? or is it a "space".  I'm pretty sure that at this point in
time, I'm sending a "space", but not sure if that's the correct way to
build the packet.  It does, however, seem to be working properly as

Yes, I am aware that everything needs to be shifted left by one  bit,
and the last entry in the string of paths has the least significant
bit set.


Greg K7RKT

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