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[aprssig] APRS Telemetry Question

Lynn W. Deffenbaugh (Mr) ldeffenb at homeside.to
Sat Oct 13 19:53:39 UTC 2012


On 10/13/2012 3:01 PM, Steve Noskowicz wrote:
>     As I said, APRS101 that I have (aug 2000) does not mention the #.  It only shows it in the example.  Therefore, the Telemetry data payload packets MUST begin with "T#nn" (and perhaps "T#n") not just "T" as 101 states.
>    With the data type definition being the "T" it seems to me that the "#" is redundant and a wasted byte, no?

I don't question the protocol specification, I just attempt to 
understand and implement it.

If you look closely at the Telemetry Report Format on page 68 of 
aprs101.pdf, you'll see that the Sequence No. is specified as #xxx, for 
a total of 5 characters.  Yes, the # is part of the protocol 
specification and not just in the examples.  Every single character in 
those format specifications is part of the specification, especially 
those highlighted in yellow.

Lynn (D) - KJ4ERJ - Author of APRSISCE for Windows Mobile and Win32

PS.  I didn't know a single thing about APRS when I started over three 
years ago.  I spent many a night reading and re-reading aprs101.pdf and 
examining sample packets from aprs.fi's raw displays.  It takes time to 
find and understand some of the nuances, but most of the basics are in 
that document.



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