[aprssig] APRS and Unicode

Greg Trasuk trasukg at trasuk.com
Fri Jan 6 12:07:49 EST 2017

Hi all:

I’m writing some APRS utilities for JavaScript (https://github.com/trasukg/utils-for-aprs) and I’m just checking my assumptions about text…  

It seems there are really two domains for APRS text content - there is the AX.25 domain (i.e. if we’re formatting a callsign for use in the address block of a KISS frame), and then there is the third-party domain (i.e. if we’re formatting a third-party message with ‘}’ or sending over the internet with APRSIS). 

Are the following assumptions correct?

- Callsigns are limited to 6 ASCII (not unicode) alphanumeric characters in the AX.25 spec, and by extension, KISS protocol:  Is this also correct for third-party messaging/APRSIS?  Are lower-case characters permissible?
- In any other text, UTF-8 encoding should be used, and non-ASCII characters are permissible.
- In the case of Unicode text, the length limitations in the APRS docs should be interpreted as characters rather than bytes (e.g. the message length specifically says ’67 characters’, not ’67 bytes’).


Greg Trasuk, VA3TSK

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