I’ve been watching – with awe – the number of high altitude balloon (HAB) launches there are here in the UK, and thinking about building my own and sending it up. Last month I went up to Cambridge for the annual UKHAS Conference which was really interesting. Not only are people launching balloons to great heights above 30 kilometers, but there are also solar-powered trackers on “floater” balloons which rise to a certain altitude and circumnavigate the earth many times (see UBSEDS18 for an example).
I want to build one, but figured the first step was tracking. I picked up a cheap SDR module, and set off building a yagi antenna. I finished it back in August, but after the conference, I was determined to find a launch in the UK that I could try and track.
I finally got my chance on September 24th with a balloon launched in Wiltshire called “Stabilotron-II”. The launch was a slow ascent of 1 meter / second which is slower than a lot of flights, so I had plenty of time to set up. It worked!
$$STABILOTRON-II,532,11:56:54,52.7128,0.1321,16259.040,46.130,16,186,-7,3.227,31.93,31.93,27.50*4D4E
This is the first clean data sentence I received. At 50 bits / second. Over radio waves. Pretty cool!
Here you can see my homemade yagi mounted on a camera tripod, sticking out the skylight window of my top floor bathroom. I tracked the balloon with varying success from the midlands over Norwich and across the sea until it was over land in the Netherlands. The quality of my antenna & receiver setup isn’t that great – during the flight I had to make a lot of adjustments (including moving my laptop away from the antenna – makes a big difference!). My last recorded contact was at a range of about 300km somewhere over/past Rotterdam – which is pretty amazing! After that, I could receive some data, but only in patches; not enough to get clean tracking data back.
From the HAB tracking server statistics, I received 221 “sentences” which isn’t much compared to most of the other receivers, but not bad for only £30 in parts.
For software, I used:
- dl-fldigi v3.1 on OSX
- HDSDR bundle for OSX which includes rtl_tcp (my USB SDR is a RTL2832 + R820T2)
- Soundflower for audio routing from HDSDR to dl-fldigi
I’m fussing with a raspberry pi to build a dedicated tracking machine for future flights which I’ll surely get done one of these days.
The experienced trackers are clearly a lot better at this – but hey, I parsed 221 messages, which ain’t bad for a first go :)
Next step: actually assembling my own HAB payload and launching it!
