[aprssig] A New "Space" Trend ?

Stephen H. Smith wa8lmf2 at aol.com
Fri Feb 6 18:15:22 CST 2009

KB5ILY - Travis W. Burton wrote:
> Maybe I haven't noticed it in the past, but I have noticed several new stations 
> inserting a space between CALL and an SSID.  Plus the SSID is one or two 
> letters rather than numbers.  Only one example of this in my stations list 
> would be:
> Is space a valid character per the spec ?

APRS is an application layered on top of the 30+ years old AX-25 packet 
radio protocol and standard. 

For **RF** operation, the SSID format MUST conform to the underlying 
AX-25 standard, and be a hyphen and number between 0 and 15.  [The 
packet standard only provides a single 4-bit nibble for the SSID field, 
meaning only 0000 through 1111 ( binary equivalent of 0 to 15 decimal) 
will work.] 

APRS **Internet** operation is NOT constrained by the limitations of 
AX-25 and the packetizers/de-packetizers in TNCs. (You are just passing 
strings of text  through a Telnet connection to an Internet server.)   
Any arbitrary characters can be placed in the SSID field, -IF- you don't 
want the packet to be gated to RF.

For example the three instances of UIview in my ham server setup that 
receive-only off RF, and never transmit, use the "fake" SSIDs of 
WA8LMF-16, -17 and -18 to conserve the "real" SSIDs for on-air RF use.  
The fourth instance of UIview which does transmit on RF uses -15.



Stephen H. Smith    wa8lmf (at) aol.com
EchoLink Node:      WA8LMF  or 14400    [Think bottom of the 2M band]
Skype:     WA8LMF
Home Page:          http://wa8lmf.com  --OR--   http://wa8lmf.net

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JavAPRS Filter Port 14580 Guide

"APRS 101"  Explanation of APRS Path Selection & Digipeating

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