Tony Giacometti wrote:

Roy, you scared the daylights out of me for a minute,

By the way, any idea why this loop might be under performing?

Well, first of all, I think the problem might be your expectations. A
small loop has a very broad pattern, with a couple of very narrow and
deep nulls. If you have noise coming from a very narrow angular region,
you can use a loop to null it out. But if it's coming from the wiring in
a neighbor's house, is getting on the power lines, or otherwise comes
from a range of angles, the loop won't help. If the noise is getting
into your house via the mains wiring, then the loop will probably make
things worse compared to an outside antenna, since it's closer to at
least one source of the noise.

And this does seem to be the case. Although you didn't say in so many
words, it sounds like the signal/noise ratio is worse when using the
loop than when using the outside antenna. If so, then the last couple of
sentences in the above paragraph apply.

In a recent posting you say the noise level comes up substantially when
you connect the loop, so you can quit worrying about your receiver noise
figure in my opinion -- and with it, the AGC operation, S-meter
calibration, and so forth. It means that external noise is considerably
louder than receiver noise. You can also quit worrying about how many
turns. A preamp, or even an audio amplifier connected to the receiver
output, will make both signals and noise louder, in the same ratio, if
they're not loud enough to hear.

So the only thing which can be wrong with the loop that you can't fix
with a little amplification is that maybe it's poorly balanced so the
nulls aren't what they should be. The only way I know of to test for
this is to rotate the loop when listening to a distant station or a
small battery powered signal source -- something coming from only one
direction. You should be able to null it out pretty effectively. If you
can't, the problem might be loop construction or it might be proximity
of other conductors warping the pattern. If you can successfully null
out point-source signals, then the loop is performing as it should. And
if that's not good enough, then a loop isn't the solution to your problem.

Roy Lewallen, W7EL