Hi all,
Since a few hours i'm running a higher power on 2970 Hz. My own grabber
shows an increase of 5 dB. The measured antenna current is now 44 mA,
see
https://dl.dropboxusercontent.com/u/19882028/ULF/44.4mA%402970Hz.jpg
(with the Heidelberg castle in the background ;-) ). This should mean 5
kV on the antenna and 250 nW ERP.
A suitable capacitor is now in parallel to the antenna. It seems to
have a high temperature coefficient. I'm trying to stabilize the
working point of the system to keep the current constant...
270 mA is now running though the yoghurt cup coil which was used on
6.47 kHz in the past. Maybe the internal iron powder cores begin to
saturate slightly at this current and frequency? This could explain the
higher losses and the lower resulting voltage or antenna current.
Actually i did expect 57 mA...
73, Stefan
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