In the event GPS receiver or APRS transmitter were to fail, HAB1 had a backup that allowed recovery team to locate it. 100mW radio beacon from BigRedBee transmitted “beeps” every 5 seconds on a pre-defined frequency. Finding the beacon is not as easy as driving up to GPS coordinates, but there are a few techniques to locate it:
- Fox hunting – using directional antenna such as Yagi antenna to get a bearing to the signal
- Omni-DF – finding three locations with equal signal strength, and estimating beacon’s location to be at the center of a circle formed by those three points.
The best part about radio beacon is that it does not depend on any other technology (like GPS signal, receiving antenna, cellular service, etc). The beacon keeps beeping as long as it has power.
Beacon was configured with:
- Transmit on 438.600 MHz frequency
- Beep frequency once in 4 seconds (0.5s transmit / 3.5s idle)
- Transmit my call sign every 5 minutes along with battery voltage