HAM radio
WB8WGA’s Simple Inexpensive TNC
A terminal node controller (TNC) is a device used by amateur radio operators to participate in AX.25 packet radio networks. It is similar in function to the Packet Assembler/Disassemblers used on X.25 networks, with the addition of a modem to convert baseband digital signals to audio tones.This TNC implements only parts of the AX.25 protocol, to encode and decode Unnumbered Information frames, used in the APRS system
RF Communication Between BASIC Stamps Using 2-meter HT Radios
This example uses Tigertronics RTX-12 Radio Modem and Parallax BASIC Stamp 2, though it may be substituted with any microcontroller. The example includes two sets of programs: a simple version that lacks error checking and a more complete example with checksums