Toxic239 shared his wireless temperature sensor project based on the MSP430 microcontroller. It uses a 14.089 MHz carrier frequency which is modulated using Morse code, outputting “CALLSIGN T<TEMP> 73”. The source files are available in the forum.
For an upcoming low altitude party balloon flight :D we had to put together a simple Morse transmitter. The idea is to use the cheapest MSP430 (USD 1.27 on digikey) to measure temperature and send continuously a simple message “CALLSIGN T<TEMP> 73”. The generator and RF power amplifier is built using 74AC00 and a quartz for 20m (14.089 MHz) with output filtered via a Pi filter.
Via the forum.