Kamtronics KAM - $50
This is a basic mid 1980s digital interface. AFAIK it does packet, RTTY, FSK and AMTOR, which means it would be useful for 2m and HF things like APRS and maybe Winmail, etc.
'91 Toyota Pickup
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"They say the test of literary power is whether a man can write an inscription. I say, 'Can he name a kitten?'" -- Samuel Butler