Hi group,

I'm a SWL and am specially interested in Navtex DX-reception.My problem
is (was) the heavy QRM from about every TV-set, monitor, PC in the
neighbourhood.

I'm currently using a T-aerial: horizontal wire 20 meters long, ca. 10
meter above ground, vertical part ca. 10 meter down from the middle, =
1:9 "magnetic" balun = 25 meter RG58 to receiver. Receiver is located
on the first floor, and is grounded via a thick wire to the earth pin
of the house. Typical reception sounds like this:

http://users.pandora.be/dirk.claessens2/div/not_grounded.wav

....humming, hissing, hard to decode, nightmare.

In despair - and against all advise in antenna textbooks (ground
loops!) - I decided to make an additional earth point at the balun. I
drove two 1 meter 1/2 inch copperpipes into the ground, and connected
these to the shield of the RG58 at the balun. Grounding at the receiver
was unchanged. The result was stunning:

http://users.pandora.be/dirk.claessens2/div/grounded.wav

QRM totally gone!
Can anyone explain this?

Thanks for any insight - Dirk