Our 2m (146.43MHz) emergency uplink system needed a powerful radio to make sure we could send emergency commands to the rocket. We had some surplus Mocom radios - old VHF radios from the early 1970's - which can put out about 50W max.
We've used the Mocoms for LV1/1b and are continuing to use them for LV2.
and attach it directly to a device which generates DTMF signals.
- Information on LV1/1b's 8051-based DTMF generator box.
- For LV2, we've moved to a PC running a small java app (along with DTMF dial) and a small adapter box to hook the PC to the Mocom.
Uses crystals to get RX/TX = 146.43MHz
The radio's connector (what we call the "head"):
Shot of the inside of the Mocom radio: note the added diode and the power out adjustment potentiometer.
Closeup on the added diode since we'll surely have to do it again: It's a 1N4001 diode which should kill the back-EMF of the relay coil so that we don't blow the mocom driving circuit.