On 07 Dec 2010 23:11:16 GMT, Sébastien MEDARD wrote:

Now, I get a poor wire from my flat to the ground (near the ground). It
gives me some night reception for broadcast from 500 KHz to 1500 MHz (it
is quite interesting, but quite limited too...). Except that, I get
nothing. Frustrating.

Hi Sebastien,

Use an antenna tuner (same thing Amateurs use, but without the
meters).

You probably need this because of the Broadcast transmitters. Those
transmitters can force your radio to create an AGC voltage even when
you are not tuned to the Broadcast frequency. This AGC voltage causes
your radio to lose sensitivity.

To put it another way, suppose:
you have a strong Broadcast station nearby on 1 MHz;
you connect your radio to a long antenna for SWL;
you tune to the 31M band;
the Broadcast signal creates a very strong AGC;
you (naturally) do not hear the Broadcast signal;
you (un-naturally) do not hear many 31M band signals.

To solve this:
Add a tuner;
you adjust it for the 31M band;
it removes the Broadcast signal;
your AGC voltage is now based on 31M band signals;
your radio becomes very sensitive;
you hear more 31M band signals.

This will also work for weak Broadcast signals.

73's
Richard Clark, KB7QHC