PicoBalloon Challenge 2019

PicoBalloon Chalenge 2019 was held in Brno on Monday, 4th March and was organised by SOSA - Slovak organisation for space activities and Brno Observatory and Planetarium in cooperation with S.A.B. Aerospace and Czechinvest.

I noticed this competiton in January 2019 but my idea was to visit the observatory to see the teams and their radiosondes. My friend Vlada (OK1FET) sent me a message three weeks before the event that we could join the competition as he tried radiosondes in the past. We discussed the details a bit more but I found that Vlada had his radiosonde nearly prepared, so I decided to build my own radiosonde as well.

The idea was to trasmitt a morse signal (CW) on short waves once per 10 minutes and to use RBN (reverse beacons) for detection and monitoring. Even though the idea was simple, it was quite challenging to get everything done on time.

My radiosonde contained two switchable oscillators that worked at 7MHz and 14MHz, one small amplifier, low pass filter and a microcontroller. All of that was powered by solar pannels. When the PCB arrived and a prototype was working, I spent most of the remaining time reducing the unwanted harmonic signals (especially those which were not inside HAM bands) to make sure that my radiosonde does not produce any interference. This part was successful as can be seen from the measurements (the second harmonic was reduced by 40dB at 28MHz and the third harmonic was below the noise).

I finished both firmware and soldering at 10AM when some of the teams were probably at the observatory. I arrived at 12 o'clock. The official start (launch) was at 1PM. We were given some instructions, balloons with helium and we could go for launch. It was actually much more difficult than I expected due to the wind speed. I managed to break my antenna during the first attempt. Fortunately, Ondra (OK1CDJ) was very kind and lent me his soldering station, so I could fix that. I checked that everything worked and launched the balloon. I must say, it was a very stressfull launch. The radiosonde nearly hit a tree, hit a roof (unfortunately not as nearly :)) and finally gained some height.

Even though the reverse beacons haven't received any signal from my radiosonde yet, I really enjoyed the event, met some very nice people, learned new things both during the development and the event itself and I have a lot of new ideas for next year.

And finally, a big thank you to the organizers of this event and I hope that we will see each other next year again.

A short video from testing: