What I want to do
fly a high altitude balloon and get it back. This means tracking where it goes and calling home. I want to use GPS to track the flight, and see what different radios will send back location data.
My attempt and results
I thought I would do this through APRS, an amateur radio data network, but with the advent of cheap satellite-based commercial trackers it is cheaper to buy a pre-made device. I went with a Spot 2. It cost $60, but the Iridium satellite service costs $150 per year to send GPS coordinates every 10 minutes when it is on. Luckily, I can transfer the service to a new device if I lose this one. That is appealing. And its satellite system doesn't require an amateur radio license.
I could have gone with other satellite systems. things like:
- Habduino, an arduino telemetry board that costs 105 british pounds.
- Build-my-own Spot clone with Sparkfun's plans for their discontinued product.
- Use the RockBLOCK, a serial modem for sending 50 character text messages into Iridium for ~10 british pence a message.
Amateur radio systems
I have an a amateur radio license for doing just this very thing, and have looked at it. The amateur radio system I liked was an all-in-one transmitter called the BeelineGPS. I also looked at were the Tiny Track 4 and a transmitter, a system of this sort., But this radio would probably not be able to communicate with a tower at lower altitudes. So with an amateur radio system, we would need a ground tracker
[Doppler radio setups]
Finding the direction to the transmitter requires one to measure phase difference of pseudo-doppler signal against a known reference (e.g. 'North'). The pseudo-doppler signal is introduced (superimposed on the demodulated signal) by electronically rotating the antenna array against a reference signal of the same frequency as half the switching rate.
Questions and next steps
I got the Spot... I need to fly the balloon. It seems to report more regularly when facing upwards.