The only connection this post has with SOTA is it is about transmitting radio signals at altitude - which is I guess what SOTA is all about and it may therefore be of minor interest to some.
On Wednesday I launched a small balloon from my house which was carrying a solar powered payload fitted with a GPS and radio transceiver. The all up weight of the complete payload was 10.2 grams, which is on the heavy side as some have been made at 5g or even less but i’m using off-the-shelf components not a custom made board.
I should stress the launch was done with the approval of the UK Civil Aviation Authority and a NOTAM (Notice to Aviation) was issued warning pilots near the launch site.
The radio is transmitting on 868MHz and is using The Things Network (TTN) of gateways which cover most of Europe. It has caused a bit of controversy in TTN circles as it is transmitting every 30 seconds which is too often and violates the TTN Fair Use Policy. In my defence other balloons have been launched with this interval including one by me without any fuss but I seem to have been given a reprieve and the pitchforks have been put away.
The balloon is currently moving south down the UK and has just left the Lake District. On this link you should be able to find it as “ttnwiv4n”.
The website is a bit flaky and if it doesn’t load quit out and try again. If you click on the question mark on the far right of the menu bar the Welcome panel on the right should vanish.
The blue circle shows the distance from the balloon where it would just be visible on the horizon, the green circle shows where it would be five degrees above the horizon.
It won’t be possible for any amateurs to communicate with the balloon as the LoRa transmissions are encrypted and are transmitted on 8 different channels with a different channel being selected at random for each data packet of lat, long and altitude.
If you select on the Tracker website to view 3 days of data you should see the flight path which starts near Plymouth and heads west. In the evening it shut down and I didn’t expect to hear from it yesterday as it was going to fly too far from land but for a short period it was heard by one gateway* which is where you can see a curved path between Scotland and Iceland. It then woke up this morning over Central Scotland and is being plotted. The straight lines on the path are of course the times when it was not in contact.
*From its ID number the gateway hearing it was near Emden in North Germany. I am not sure if this is correct but it might be just remotely possible some sort of ducting occurred but no website I could find yesterday suggested the conditions in that area for Sporadic-E or Tropospheric Ducting were in any way favourable. I’m putting it down as “unexplained”!
A picture of what the payload looks like is shown below. The balloon supporting it is a 36" clear £1 balloon from AliExpress and is filled with 95% helium - “party gas”. Hydrogen is much better but it is expensive to get set up for using hydrogen. It was launched with two balloons tied together but given the altitude it has reached I think the upper balloon has parted company as I had expected an altitude above 10000m but it has settled at the same height my first balloon did which was launched under a single balloon. It seems my balloon tying skills need to be improved!