On Wed, 26 Sep 2007 09:14:16 GMT, Navtex-Fan wrote:

BTW, it has been raining over here for 2 days, and the QRM levels are
still fine!

Hi Dirk,

Great. We've been fog bound.

I recently bought a $40 SWL radio, and its noise comes from the
display with about 3 MHz bandwidth around the 49M band. I will soon
pop it open for some corrective surgery.

I have also done the following experiment: Instead of the commercial
"magnetic balun" I was using, I have now rolled my own 1:9 unun. The
main difference with the MLB is that the unun has isolated windings.
The primary is grounded to the earth rods, the secondary is grounded
via the receiver. I thought this was a better solution with regard to
ground loops.

Not really - it may cast the problem into a different coupling
mechanism. You still have capacitive coupling and you want to ground
the smallest signal end (the antenna), not the load end (the
receiver).

However, it sounds like it didn't make a substantial difference, or
any difference (seeing as you would have mentioned performance). This
suggests you have driven out as much noise as you can. Anything else
is coming in through the air from afar.

I've read (and tried) all the "expert" SWLing opinions of what pass
for BalUns (even professionals rarely get it right) and experience
still shows a tuner performs better - unless, of course, you really
have a sloppy installation (no choking, poor grounds, poor balance,
running lines past noise sources, the usual stuff).

73's
Richard Clark, KB7QHC