Documentation/networking/ax25.txt

To use the amateur radio protocols within Linux you will need to get a
suitable copy of the AX.25 Utilities. More detailed information about
AX.25, NET/ROM and ROSE, associated programs and and utilities can be
found on http://www.linux-ax25.org.

There is an active mailing list for discussing Linux amateur radio matters
called linux-hams@vger.kernel.org. To subscribe to it, send a message to
majordomo@vger.kernel.org with the words "subscribe linux-hams" in the body
of the message, the subject field is ignored.  You don't need to be
subscribed to post but of course that means you might miss an answer.