Max Transmitting Power: 300 mW
This is the radio we currently use for our secondary communications
payload. It pre-set to the national APRS frequency (144.390). We
typically transmit once every 2 minutes. Since we are using the
national APRS frequency, we can check findu.com for the last reported
position. We only check online when loose track of the balloon during
the chase (an iPhone comes in handy for checking online). This also
allows other not at the launch to monitor the balloon's progress in
near-real time. We use a home-made J-Pole antenna with the MicroTrak.
Even with the high gain of the J-pole antenna, we typically get a
"ping" from the secondary communication payload when we are within a
mile of a the payload lying on the ground.
Many other BalloonSat's use this as their primary radio. We are not
This radio is extrememly small and light. Our tests show we
can run the radio and GPS for over 17 hours on an 8 pack of AA
Energizer Lithium batteries (12V).
We found out the hard way that the MicroTrak reports the last known GPS
location, even if a GPS is not connected to it. During one launch, we
thought we had GPS lock (the reported position was the launch site) but
in reality it didn't. ALWAYS make sure the APRS is reporting
altitude as well as position (Lat/Lon). The TinyTrak will not
report altitude if there is no GPS lock.