By Peter, DG4EK
Hunting sondes started in Idar-Oberstein we have been very surprised last Thursday. As we (my XYL and me) have been to the so called Grosser Feldberg, that's about 50 km north of Frankfurt/Main, it's 860m a.s.l. !,
I switched on my RX and found a good AGP signal on a different QRG. It was on 403.650 MHz. As I tracked the sonde looking on its footprint I found that it might have been started anywhere in the southwest as suddenly balloon bursts unexpected at only 11000 meter! This happened to be an error as you soon will see.
I thought this might have been a failure of the balloon and I went on tracking the descent. It came down very slowly at only 1,9m/sec! As it just was about 200m above the ground I suddenly saw that fieldstrenght suddenly went up again.
Strange!!, I thought to myself and turned the antenna a little bit. I was even more suprised that I now got an even more stronger signal. Looking to the GPS data sent from the sonde I found a big jump in location of about 80km!
That was impossible! Have I been tricked by a bad almanac?
No indeed QTH of the sonde has really changed. Verifying the serial number I found the reason. That must be another, a new one just started. Also packet number was only 400 or so.
Now I also saw that it must have come from Idar !
I also tracked that sonde completely and noticed its landing point for later finding it.
This all happend 4 times and every time balloon bursted between 7700 and 11000m !
All in all Idar-Orstein launched 4 sondes in between 4 hours (1 launch per hour).
At noon last sonde has landed so I could start to find them all.
The first I found didnt gave me the parachute. It was hanging in or on a tree about 20m above the ground but I noticed that the sonde had a different typ number. It wasnt a RS92-AGP but a so called RS92-BGP ! Later I found at Vaisala homepage that BGP is the same like AGP but with other testing conditions (EN number). Those BGP are the best tested ones !
The second sonde I found gave me the parachute too. It was landed in a fruit field (apples). It also had a radar reflector of 30x20cm and a BIG parachute of 1m diameter!
That was the reason that all of these BGP sondes started one after another came down so slow!
The balloon (the rest I got of it) is also of another typ. Its a red one made of rubber (no latex). Its the type people are using on parties but of course much bigger! That's the reason why they bursted so fast. Rubber balloons cannot fly higher than 10000-11000m.
I now have 4 pieces of that type of sondes having 4 big paras (got only 3) and r-reflectors.
On my recherche in internet I found that these sondes are so called "ceiling balloons". They are started sometimes (no schedule exists) to find out the ceiling, the beginning of the lowest clouds and are watched by eye disappearing in the clouds. Thats the reason why they are using RED rubber balloons. The radar reflector looks like a normal double bended sheet of strong paper. It must contain (not visible) some kind of electrical conducting particles. I havent found out yet what it is exactly. I guess Idar added them because balloon flew to Frankfurt airport on this day.