Thanks for these great explations !!
OK, I understand that my previous explanation are not very clear, I made confusion between several abreviations !! I use H instead of L.
U1, U2 and U3 are the value obtained with the help of a multimeter, and E1, E2 are the value found with the oscillo (mVolt pic to pic).
I think that the bad reproductibily of the mesure are coming from the generator I am using : it is a very basic sound card with a simple sofware ! I will made one in the next weeks with XR-2206 element (
https://www.electro-tech-online.com/custompdfs/2008/11/0003.pdf.
Here are other picture of the signal obtained with a simple coil (2 different in fact). First have been post here :
https://www.electro-tech-online.com/threads/how-to-design-an-antenna.84693/#post658644. It seams that there is no modulation. Did I am correcte ?
I will search for band pass filter. What did you suggest as first approch : an active or a passive one ?
Jean-Marie