[aprssig] Object Naming Conventions

Pete Loveall AE5PL Lists hamlists at ametx.com
Sat Feb 25 06:50:24 CST 2012

See below...

> -----Original Message-----
> From:  Lynn W. Deffenbaugh (Mr)
> Sent: Saturday, February 25, 2012 6:12 AM
> Well, since the ! or _ are the name delimiter, by spec definition it won't be in
> the item's name, the name will just be shorter, right?

It actually throws out your parsing since the lat/lon/symbol portion is to immediately follow the ! or _  so the packet would be improperly formatted and should be rejected.

> And since part of the OBJECT server's task is to generate an Item-In-Message
> response, then the object/item names created by that OBJECT server should
> probably not allow ! or _ in order to provide the expected operation.

That would be a function of the object server, not a general restriction for all object generators.  I was addressing the statements regarding all objects, not what restrictions might be imposed on the object server as this thread had been renamed to the generic "Object Naming Conventions".

> While we have the ear (er eyes) of someone more familiar with the spec that
> us newbies are still coming to grips with, is it also a callsign limitation that the
> portion before the dash contain only up to 6 characters?  ABCDEFG-N is not
> valid?  Or is valid?  I know it's invalid for AX.25 purposes, but when allowing
> character-based -SSIDs, it's a question worth asking to help guide new client
> configuration validators.

The spec was written around AX.25.  However, APRS-IS and third-party format gating to RF allowed more variances.  Early in the last decade, it was agreed among server software authors that station "callsigns" could be upper, lower, or mixed case alphanumeric, may contain a single hyphen followed by one or 2 alphanumeric characters (the SSID), and the total length including SSID cannot exceed 9 characters.  Spaces and other punctuation is not allowed and "callsigns" appearing before the SSID are converted to upper case for passcode calculation purposes.  I thought this was on www.aprs-is.net but I don't see it now.  I will add it to the Connecting to APRS-IS page.  Also, a SSID of -0 should not be used as it is unique from no SSID in APRS-IS duplicate calculations but no SSID with the callsign implies -0 (that is in the TNC2 and AEA specifications which is referenced in the APRS specification).

Because of the AX.25 specification, lower or mixed case callsigns may be (will be) converted to upper case by many clients and client software.  While lower/mixed case is allowed and considered unique to APRS-IS servers, that is not (and should not be) assumed to be true at the client.

Hope this helps.


Pete Loveall AE5PL
pete at ae5pl dot net

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