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After the initial euphoria of finally having found another sonde hunter near me, who was also on the same wavelength as me, we naturally wanted to go hunting together. I had to wait for the suitable opportunity, if he had time I had none and vice versa, or the sonde weather was not favorable. On 10.02. we finally had the suitable opportunity, we both had time, and the sonde forecast from Beauvechain was favorable, between Gummersbach and Cologne. I took the train at 21:23 to Rösrath, where Kevin and Christian picked me up in the Volvo, which is decisive for his nick, and already has several hundred thousand kilometres on the clock.

Since there was still time until the launch, we paid a visit to P3440172, the Essen midday sonde from 21.01., which was hanging high in a tree nearby. Unfortunately she still did, and we used the time until the sonde was near us to chat in the car. When it was foreseeable that the landing area would probably be somewhere in the Bergisch Gladbach area, we set off in this direction. Hardly arrived, the balloon burst in barely 18000 m and would remain on the other side of the Rhine river; landing somewhere northwest of Cologne. Over the run-down Leverkusen bridge we went to the sonde, which was meanwhile approaching Pulheim, and landed there at the access road to a main road in the field. Less than ten minutes later we were there. We fought our way through a blackberry-covered embankment to the landing site, which was covered with high grass. At some point we where stopped by the sonde string. The rest was routine. Small balloon residue, parachutes are not used by Beauvechain.

Because we weren’t tired yet, it was decided to visit the De Bilt sonde from 14.01., P4030485 in a tree south of Düren, which was received by ON-1 until the battery failed, to see if it had fallen down in the meantime. Unfortunately it was still hanging in the tree, and Christian couldn’t hit it with the sticks he was trying to throw at it. Unfortunately we all didn’t have any sticks at that time.

The Meppen morning sonde from 07.01. first wanted to approach me exactly, but then landed about 10 km air-line distance from my QTH. From the TH I took the RB to Marienheide, which only has hourly service, while the sonde was still in the air. The last prediction I had on the train pointed to a somewhat more northerly landing, and the bus in this direction departed at the same time as the train arrived. With a few minutes old prediction I ran to reach this bus, which also only departs hourly, and managed to do so. Unfortunately, as soon as I checked the last data of the sonde, it turned out that it had landed a little more to the south, and I was driving in the wrong direction. Half as bad, the bus in the opposite direction arrived in 15 minutes. That gave time to forge the plan. The landing area around Dürhölzen had many small woods and meadows and because ON-1 was down, I didn’t know exactly if the landing place was in the forest. A school bus took me there, back I would have to walk the five kilometres to the station. What one one does for his sonde

After a snack at the bakery I started. As I was allowed to learn here in the village the bus driver knows every child by name, and so I was of course the one sticking out. After I had explained my mission and pulled out my laptop to see if the probe was already audible, the crowd was highly fascinated by my Moxon made from Lego-Technic. I first had reception in the village, and unfortunately the probe had landed in the forest.

There arrived the parachute could clearly be seen with large balloon reaminings in a leafy tree above the forest road in a height of 6-8 m. There was no trace of the sonde. The GPS data pointed to an adjacent spruce plantation in which the string disappeared. DFing with the Moxon and SDR didn’t work, moreover the landing area was a valley, everywhere reflections. My lack of experience adds to that. Frustrated, I went on the journey home, the drizzle matched my mood.

At home I evaluated the GPS data of about 20 minutes again, and noticed a very high variance. The averaged values were much closer to the forest path than expected, but fluctuated by about 50 m. Since the sonde was definitely hanging in a tree, the bad GPS reception indicated a position in the middle of the branches.

Today the weather was perfect and I undertook a follow-up check with a friend who is into fishing. The parachute had disappeared and was not to be seen on the ground under the snow, probably it had already fallen down and been taken away. A rough optical check around the interpolated position didn’t help, and at the end of the sonde string, which we caught, was nothing. Before we gave up, a thorough optical check was performed. And in fact, not far from the path, the sonde was lying on the snow. So it could only have come down in the last few days. The sensor arm was in a very poor shape, but it didn’t show any error when turned on.

After the last Essen sondes had not made it to a position uncomplicated to reach, P3530031 broke through this series. The prediction was at first southeast of my QTH, between Wiehl and Waldbröl, but thanks to the early burst below 25000 m the landing shifted some kilometers to the north. Despite the low descent rate the probe didn’t fly as far as I expected and landed northwest of me in the Gelpetal in a forest. So far the nearest landing site to my my QTH since I’m into radiosondes with 6.62 km as the crow flies (in 2017 two landed within sight of my window, but I didn’t knew anything about them…)

A friend, who lives a little over a kilometre from the landing site, had asked me to let him know when I would be hunting in the vicinity of his house. I wrote him at night and we arranged to meet in the morning. The first bus would arrive there at 8:10, I hoped that the probe’s batteries would do that despite the cold weather.

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Arriving on site, the fact that only 400 m away from the sonde the signal level was sufficient for decoding, made me hope for a ground landing in the forest. So it was, probe lying on the ground, parachute and big balloon remainings approx. 20 m further in the tree. Unfortunately the balloon remainings could not be abseiled. The large remainings of the balloon could also mean that the balloon did not burst completely, but leaked helium bit by bit. The probe shows traces of corrosion on the broken sensor arm, which surprises me after only one night in the forest.

For the first Meppen sondes of the new year, the prediction showed a landing almost at my front door. The wind was and is very extreme at the moment, sondes fly to places where one would hardly expect them. Unfortunately all three sondes on 02.01. scattered quite strongly. The first sonde had a burst under 17 km and fell very fast, but landed exactly at the prediction, which was for a working parachute and average burst altitude. The morning sonde had an excellent parachute and flew almost 150 km further south. The midday probe finally seemed to land well for me, but descendet faster than I thought and only made it to Radevormwald.

So I discussed the strategy with flynamic, who was exceptionally not in Bonn at university. It was clear that all sondes would land further west the next day. However, Cologne is easier to reach than Radevormwald. But if prediction and probe behaviour were to spread like this again, it would be pure gambling. So it was decided to make a trip to Radevormwald. Jason, who had only taken part in an unsuccessful sonde hunt by now, also had time and came with us.

As usual with car searches I booted my Macbook into Windows a few kilometers before the landing site and opened the toolchain. But the RS41 Tracker had a New Year present for me “This Engineering Version of RS41 Tracker is expired”. I totally forgot. So I downloaded the new version via mobile hotspot, unpacked it and “Your PC is incompatible with this Application”. No simple debugging, to be honest I didn’t feel like debugging at all. We had already narrowed down the landing site to a 100×500 m strip, so DFing was the easiest solution, albeit with the Macbook in hand. (I hadn’t taken the new Baofeng and my attenuators with me to the TH, because I didn’t really expect a hunt, and only packed the Moxon and the RTLSDR).

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We looked for a parking place and got the equipment ready. Before we could look around and find out if there was anything to see, a local resident came. We explained our intentions and he had already noticed the landing site about 350 m away at the edge of the forest and showed it to us. Parachute and probe lay on the meadow at the edge of the forest, the string hung on the last tree. The recovery was easy, the unroller not completely unrolled. Third N sonde, second ABS sonde, first BW sonde with intact salvaged parachute. No more meppen style cardboard :cry:.

The sondes on 03. and 04.01. flew to reasonable positions, but I didn’t have time to take the train to Cologne in the morning and since ON-1 is down at the moment, there is no cold search at the weekend. But at least one more launch site in my CV, increasing the number to five so far.

This morning it was foreseeable that Uccle could be something this morning, if not for me, then for Kevin DO1KMT in Troisdorf. But the sonde accelerated and rushed with 380 km/h towards my QTH. Unfortunately a little south. The burst just before the airport Cologne-Bonn fit, but the parachute worked quite well during the descent and the probe was far behind Morsbach near a village called Birken-Honigessen.

Somewhat far for us, especially because I had to give a tutorial at 16:30 (but with another tutor, so there were still possibilities here) and the Bremen prediction was still in the forest. After a short linear interpolation it looked more like a field landing and my cotutor didn’t mind to do without me and so Kai and me set off.

Google Maps led us to the landing place from the south (mountains and so on) so that I already had reception 6 km away from our destination, about 3.5 km air distance from the sonde, with a 433 MHz magnetic foot antenna inside the car. Nothing that can be decoded with the RS41 Tracker (I have to put my current toolchain with Zilog on the Macbook), but quite strong. That didn’t give me much hope. The reception disappeared, and with it came my hope back: maybe it was a line of sight to the landing place on a mountain facing the road?

Until 400 m to the prediction there was not enough signal to decode, so that only then I had the certainty that the sonde was in the forest. (As it turned out in the aftermath, not 5 m from the prediction) But at least in a not so dense leafy forest, somewhere between undergrowth and real forest. So the car was parked on the nearby farm where we were greeted by three pony-sized dogs and explained our presence. From there over the fields into the bush; the parachute hung in approx. 7-8 meters height at a branch, the probe approx. 3 m under it. Shaking the tree caused the probe to sink by at least a few decimetres.

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Since the branches on which the parachute was hanging and kept the probe from sinking were relatively thin, the plan was forged to push the probe down with one of the thick and long branches lying around. Unfortunately, most of them were already so rotten that they broke when they were lifted. In some distance I was lucky and found a long branch, which had to be bent over in a more recent storm, held only with a piece of bark on the stem and was about 6 m long. We carried it with combined forces to the sonde and at the upper site of the branch was arranged in such a way that a Y-fork was formed, which could be put around the cord on which the sonde hung, in order to then pull it down. The plan worked and when the probe was down even the parachute could be pulled down undamaged by pulling the cord. The Totex parachutes are massive; the big red ones made of plastic by BW and KNMI would certainly have been broken. The only loss is the temperature sensor, which is more the rule than the exception for tree-landers, especially if you have to use force.

Back at the TH, were I still was present in the las ten minutes of my tutorial (yikes) everything was examined: The sonde was in the air before, the ozone sensor comes from Droplet Measurement Technologies and has the serial number Z22756. At the top two dates are crossed out: 15.10.2018 and 13.05.15.

The probe looks as if it has been outside longer. The ring at the top is rusty and it has an interesting smell of its own. The water battery was present this time, not as with De Bilt where I was disappointed when unpacking, and this time also a heating battery is present. It’s a 9V lithium block brand Conrad Energy – didn’t even know that Conrad is also common in Belgium.

The sonde itself is a RS41-SGP, and (not to my surprise, DO1KMT had snatched one from the same batch in Wuppertal a few weeks ago, so we got to know each other) an N-serial number sonde in an EPS case. Since Uccle uses the plastic holder for dowelling and not only glues the sonde on like De Bilt, and the holder has the date code 5/14 at the back, we can now also say that the EPS probes don’t need any other holder.

The OIF board has the serial number M3330067.

Interesting to see the small differences between Uccle and De Bilt, and two ozone probes in 10 days are of course also great. Unfortunately both recycling probes. I think if I catch new probes, I’ll replace the styrofoam and send the old one back…

EDIT: As it turns out, Happysat already catched the sonde in 2015 when it landed in a forest near the Dutch/German border and sat on a tree for a few month. He returned it in september of 2018 and probably after another flight in October, which ended in a residential area in belgium, this was the third use of the sonde. Photos from Happysat are attached.

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