AX.25 has no FEC but there is FX.25 which is an encapsulation of the AX.25 packet with a preamble at the front and reed soloman at the end. But the issue is the

AX.25 has no FEC but there is FX.25 which is an encapsulation of the AX.25 packet with a preamble at the front and reed soloman at the end. But the issue is the speed of AX.25, 1200baud is dreadfully slow to be adding much onto the packet. The FX.25 protocol is a neat idea that allows for old TNC hardware to still be on the air. However, TNCs can be built with the cheapest of the raspberry pi clones so there really is no good reason as to why things can't progress to something like FX.25. There are certainly limitation to using 1200 baud AFSK but moving outside of the audio band, you could get some higher data rate but maybe loose some dB.