Cannot receive RS41 signal with the small antenna

[fermars]

Hello!,

First of all thank you for the programming team that make this project available for everyone and Mirko for letting me enter the forum.

I have just received the TTGO, upload the software and apparently everything is ok. I have modified the antenna that comes with the TTGO following the instructions to get better reception signal on the 403Mhz. Ready to use and waiting for an upcoming RS41 launching (40Km away) last night, I was very upset because I haven't receive any single packet of the Radiosonde. I used several different kind of antennas but no luck.
These are the antennas I used, some of them are good quality comercial ones and others that I made myself just to try:



Then something weird happened, I tried to use another kind of antenna, not directly attached to the SMA connector of the TTGO but the magnetic antennas that you usually use to track and follow the Radiosondes on the roof of your car while driving. I mean this one:



For my surprise, the very moment I connect the SMA connector to the TTGO it begins receiving every single packet of the RS41.

On the other hand, I have heard that the CH9102F version is not as reliable as te CP2101,
Could it be the CH9102F affect someway the signal reception?
What is the maximum range that you expect to receive and decode a launched RS41?

Any ideas or clues are welcome.
Thank you.

[IZ4PNN]

Hi,
did you do the calibration?

viewtopic.php?f=6&t=18&sid=5bbca6f9f561 ... 088b929d95

[Thierry50]

hi, I personally use this antenna on my TTGO and I have very good results, I decode the RS41 probes at more than 150km, and when I plug in a magnetic SKB it is about 350km from my car.

https://fr.aliexpress.com/item/10050020 ... 6c371w1XyF

https://www.crtfrance.com/fr/antenne-ma ... obile.html

[buttim]

Did you ever give a look under the plastic cap of the SMA antenna? Just to know if it's possible to replicate it with some copper and a connector; It seems a bit pricey at 13€...

[Thierry50]

hello, yes already disassemble, it is the same antenna as the original but longer, it is possible to redo it effectively, 13 € is for 5x antennas, so find people to make a group purchase, despite the small antenna length (spring), black plastic is important in antenna tuning.

Cdt

[buttim]

Thanks Thierry.
Sincerely I think that even at 13€ for 5 pieces it's a scam. The huge plastic cap is barely necessary since it is twice the length of the copper spiral. Quite cumbersome and not useful. I followed the instructions on the MySondy site to adapt the original and it works quite well, I think 150km away is feasible with it.
350km with the magnetic antenna is something different, I can't claim anything near that with the equivalent antenna I use in my car (actually inside instead that on the roof, might make the difference).

[Thierry50]

good evening, this afternoon I decoded the Camborne (uk) probe at more than 300 km with this same 400 MHz antenna, it has a good performance and I am not unhappy with it.
cdt

[PE1PSI]

I've not seen further response from the original poster. I have heard from another hunter who had really bad reception. When checking he did not have the 433 model. If you have the same, it will work but with a very limited range only.

[Thierry50]

good evening, have you put aluminum in contact with the antenna base, to increase reception?, again this afternoon, I decoded the RS41 probe of the camborne (UK) at 340km, and no worries