[aprssig] Use call without SSID?

[Stephen H. Smith]

Alan P. Biddle wrote:
> Hi,
>
> Locally there has been an explosion of interest in APRS, which is good.
> That has brought the inevitable argument about using SSIDs, and if so, which
> one.  Any definite suggestions about a good, current reference on the issue?  It
> is at once not very important, but also a chance to get things started in
> compliance with current best practices.
>
>   

SSIDs no longer mean anything.    The SSID technique dates back to the 
early days of APRS, before specialized APRS hardware    A mobile tracker 
consisted of a GPS receiver plugged directly into the main serial port  
of a dumb TNC. The TNC then  transmitted raw unmodified NMEA strings 
over the air. 


Since there was no way to insert symbol control codes into the raw NMEA 
data, the callsign SSID was used instead to control which of 12 or so 
symbols should be displayed.    Today, all APRS devices reformat NMEA 
GPS data into much shorter strings, and at the same time, merge control 
codes for hundreds of possible symbols and overlay codes into the  
packet data payload.     If one has both codes in the payload -AND- an 
SSID, the SSID will be ignored in favor of the codes in the payload. 


[Note further that the SSID technique, if used, cannot express the 
alpha-numeric overlay codes for the base symbols that are increasingly 
common.   


------------------------------------------------------------------------

--

Stephen H. Smith    wa8lmf (at) aol.com
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