The Joey project is a subproject in the Wombat project to design experimental radios and integrate them into flight computers for testing.
Joey-M uses the Micrel MICRF112 434MHz FSK transmitter with a dual varactor crystal pulling technique.
The prototype has four pads for test inputs and outputs, VCC, GND, TUNE and EN. Voltage is applied to TUNE to pull the crystal and increase the transmission frequency. Under testing we achieved around 1kHz shift for approximately 1 Volt on TUNE.
The Joey-M flight computer uses an Atmel AVR (ATMEGA328P) along with a uBlox NEO-6Q GPS and a Sarantel SL1202 antenna. It uses a twin-varactor variant of the crystal pulling arrangement on the prototype board, one varactor for coarse tuning and the other for fine. The bias voltages are controlled by a dual 16-bit DAC from LT controlled by the AVR over SPI.