My first radio contact from a high altitude balloon

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!


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!

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