In article .com,
wrote:

I have been trying to improve the SN, that is to reduce the noise as
much as I can, while prserving the desired signal.

This has been an on going battle evry since radio began.

The Doty antenna (http://www.anarc.org/naswa/badx/antennas/) is a
good starting place. This link (members.aol.com/WA1ION/nrants.pdf) is
a good improvement. I dropped his matching resistors and isolated the
braid on the output of the 9:1 step down. A minor improvement. Took
care of slme stubborn birdies from my equipment. I was troubled by
some odd "bleed through". While lloking into RG174 from a friend's
"hidden" antenna installation, I found a refference to an article by
John Brynt "Is Your Coax Lead-In Actually An Antenna"
(www.dxing.info/equipment/coax_leadin_bryant.pdf) that suppled some
answers that really helped me understand what is hhappening.

Snip

"Is Your Coax Lead-In Actually An Antenna"
I posted about using coax for an antenna here a few days ago. If the
coax is not grounded on both ends it can be a very good antenna. I'm
using a 40 foot coax loop to listen to New Zealand as I type this. They
are S7 to S9 nice and quiet with no interfering noise with the volume
turned up. I live in town at the beach, other homes and businesses
where there is local noise generation aplenty all around me. Yes I also
have AM stations in town a few miles away.

Most voltage sensitive antennas I have put up get noisier the lower in
frequency I try to use them. The AM broadcast band is terrible on these
antennas around here. The coax loop is as quiet or better than the
ferrite loop in a portable.

For a loop this size you should use a shielded type where the shield is
split in the middle of the loop to minimize voltage pickup. You want
the antenna to be picking up the magnetic component of the EM wave
only.

--
Telamon
Ventura, California