[aprssig] APRS Message Callsign SPEC- Ambiguity

Pete Loveall AE5PL Lists hamlists at ametx.com
Mon Apr 25 17:45:16 EDT 2016

As a clarification, the station call in -unnumbered- messages can be either upper and/or lower case but not numbered messages.  Why?  Because to acknowledge the message -directly- via RF requires an AX.25 compliant callsign-SSID which is a maximum of 6 upper case characters and a SSID of 0 ("silent") through 15.  I mention this because your example is communicating with a satellite via RF.

Just something to keep in mind...


Pete Loveall AE5PL
pete at ae5pl dot net

> -----Original Message-----
> From: Robert Bruninga
> Sent: Monday, April 25, 2016 4:08 PM
> Subject: [aprssig] APRS Message Callsign SPEC- Ambiguity
> There is an unintended ambiguity in the APRS SPEC regarding the addressee in
> the APRS MESSAGE format.
> It was intended that the TOCALL of any transmitted message could be sent to
> ANY 9 character callsign field and this included mixed-case.  Although TNC’s
> have historically forced callsigns to UPEPRCASE only, this is only a limitation of
> TNC’s and was not intended to be a limitation of APRS.
> STATION names, OBJECT names, ITEM names were intended to be a general 9
> character mixed case field in APRS padded to 9 with spaces.

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