Roy Lewallen wrote:

Tony Giacometti wrote:

it is a shielded loop and no the gap is there, thats why I am wondering
why its not doing what I thought it would do.

What you've done is to build a truly shielded loop. The notion that a
shield somehow blocks the electric field and lets the magnetic field
through is a folk tale -- an intact shield like the one you built blocks
both electric and magnetic fields. (Good thing, too, or else coax cable
wouldn't do its job.) You've just done an experiment that proves it.

The gap in a so-called "shielded loop" provides a path for current
outside the "shield" to get inside. The net result is that the outside
of the "shield" is just an ordinary loop antenna, and the gap acts like
a feedpoint to get the current inside where it can get to the receiver.
It responds to normal electric and magnetic fields exactly like an
unshielded loop. What the "shield" buys you is improved balance, which
helps prevent the feedline from becoming part of the antenna and picking
up local noise which you can null out if balance is good.

Roy Lewallen, W7EL

Roy, I don't fully understand why you made this response to me.
You mentionI built a truly shielded loop. How so? I did exactly what the
directions called for including having a gap.

If these loops are a folk tale, other than using a beverage which I don't
have the room for, how am I going to reduce the noise enough to be able to
woprk 160 and 75 meters effectively?

Tony Giacometti wrote:
Roy Lewallen wrote:

Tony Giacometti wrote:
it is a shielded loop and no the gap is there, thats why I am wondering
why its not doing what I thought it would do.

Roy, I don't fully understand why you made this response to me.
You mentionI built a truly shielded loop. How so? I did exactly what the
directions called for including having a gap.

My apology. I too-quickly and incorrectly read your "and no the gap is
there" as "no gap is there". My statement about your creating a truly
shielded loop was wrong. The loop with the gap should work as intended.

If these loops are a folk tale, other than using a beverage which I don't
have the room for, how am I going to reduce the noise enough to be able to
woprk 160 and 75 meters effectively?

"Shielded" loops aren't a folk tale, they work fine. They have a broad
pattern with, if constructed properly, narrow and deep nulls. It's a
mistaken idea about how they work that's the folk tale.

Roy Lewallen, W7EL

Roy Lewallen wrote:

Tony Giacometti wrote:
Roy Lewallen wrote:

Tony Giacometti wrote:
it is a shielded loop and no the gap is there, thats why I am wondering
why its not doing what I thought it would do.

Roy, I don't fully understand why you made this response to me.
You mentionI built a truly shielded loop. How so? I did exactly what the
directions called for including having a gap.

My apology. I too-quickly and incorrectly read your "and no the gap is
there" as "no gap is there". My statement about your creating a truly
shielded loop was wrong. The loop with the gap should work as intended.

If these loops are a folk tale, other than using a beverage which I don't
have the room for, how am I going to reduce the noise enough to be able
to woprk 160 and 75 meters effectively?

"Shielded" loops aren't a folk tale, they work fine. They have a broad
pattern with, if constructed properly, narrow and deep nulls. It's a
mistaken idea about how they work that's the folk tale.

Roy Lewallen, W7EL

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

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

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

Roy Lewallen wrote:

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.

maybe I just don't know what to expect with this loop.
Having never heard one perform I have no idea if this loop is doing what its
supposed to be doing.

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.

I powered my receiver and a few other items on a battery backup, switched
all the power off in my home and nothing changed. The noise was still
there.
Funny though, everynite between 8:30 and 9:30pm the noise reduces by half.
I keep watching my neighbors homes to see if I can tell if someone is
turning something off but no clues yet.


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.

no, the noise is worse on the transmitting antenna.
the noise on the loop is very low, and if I rotate it I can sometimes make
the noise increase as it points along the plane of the loop at something in
the neighborhood. The loop does reduce the noise but the signals are very
weak and sometimes difficult to copy.


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 nulls are well defined considering what I am using.
I have the loop about as far away as I can get it from my home and 2 others
right now. when I rotate it where it is now vs. where it was 2 weeks ago its
not very noisy.


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

The loop does reduce the noise, but the signals I want to hear are not very
loud even with the preamp. This is what the problem is.