Over the weekend I cobbled one of these together

http://www.greertech.com/hfloop/mymagloop.html

and was rather pleased with the results. My
version was made on a scrap wood hexangonal armature which allowed
approimately 15' 4" total loop circumference of salvaged RG58/u. It took
just over an hour to build, start to finish.
I tested it mounted on the roof of my camper van feeding a Sat800.
With my Barker and Williamson VR300 pi section tuner it has a frequency
range from about 2.3 Mhz up to somewhere around 26 Mhz...in short all of
the usual shortwave frequencies of interest. The tuning is fairly sharp
in all frerquency ranges, but not so much so as to be touchy. The Sat800
seems to have ample sensitivity to make up for the difference of
strength compared to the high long wire I usually use.
The most dramatic effect is the quiet! The noise floor usually
runs about S4 on the meter with the high long wire, but was reduced to a
barely registering S1 with the sheilded loop. An S6 signal is
completely in the clear. There is usually a band of RF garbage in my
neighborhood extending from about 17 Mhz up to about 23 Mhz which
normally obliterates the 15 and 13 meter bands. With the shielded loop
this was very much reduced...there wasn't a lot of activity on these
bands at the hours I was listening. I never heard WWV at 20 Mhz but did
hear one broadcaster in 13M band and some CW on 15.
I'm taking the van on vacation to the Shenandoah region next week,
will try this antenna out in the field, nd give further impressions when
I get back.



AR de KC2LVQ

William:

Look carefully at what you wrote. Couldn't you have achieved the same
results by turning the RF gain down, or shortening your existing antenna?
Noise down, signals down also? WWV gone? Hmmm. Suspicious.

--
Crazy George
Remove N O and S P A M imbedded in return address
"William Mutch" wrote in message
ell.edu...
Over the weekend I cobbled one of these together

http://www.greertech.com/hfloop/mymagloop.html

and was rather pleased with the results. My
version was made on a scrap wood hexangonal armature which allowed
approimately 15' 4" total loop circumference of salvaged RG58/u. It took
just over an hour to build, start to finish.
I tested it mounted on the roof of my camper van feeding a Sat800.
With my Barker and Williamson VR300 pi section tuner it has a frequency
range from about 2.3 Mhz up to somewhere around 26 Mhz...in short all of
the usual shortwave frequencies of interest. The tuning is fairly sharp
in all frerquency ranges, but not so much so as to be touchy. The Sat800
seems to have ample sensitivity to make up for the difference of
strength compared to the high long wire I usually use.
The most dramatic effect is the quiet! The noise floor usually
runs about S4 on the meter with the high long wire, but was reduced to a
barely registering S1 with the sheilded loop. An S6 signal is
completely in the clear. There is usually a band of RF garbage in my
neighborhood extending from about 17 Mhz up to about 23 Mhz which
normally obliterates the 15 and 13 meter bands. With the shielded loop
this was very much reduced...there wasn't a lot of activity on these
bands at the hours I was listening. I never heard WWV at 20 Mhz but did
hear one broadcaster in 13M band and some CW on 15.
I'm taking the van on vacation to the Shenandoah region next week,
will try this antenna out in the field, nd give further impressions when
I get back.



AR de KC2LVQ

"Crazy George" wrote in message
...
William:

Look carefully at what you wrote. Couldn't you have achieved the same
results by turning the RF gain down, or shortening your existing antenna?
Noise down, signals down also? WWV gone? Hmmm. Suspicious.

I'll answer for him, ...No and No.
Receiving loops aren't about signal strength they're about improved Signal
to Noise **Ratio**.
Not hearing 20 MHz WWV at the hours he said he was listening (late eve?)
means nothing as that band folds late at night or propagation simply may not
have been favoring a path between them at that time.
Try some Google-searching for receiving loops, lots of info.

XC

On Tue, 13 Jul 2004 10:56:16 -0400, - XC - hath writ:

"Crazy George" wrote in message
...
William:

Look carefully at what you wrote. Couldn't you have achieved the same
results by turning the RF gain down, or shortening your existing antenna?
Noise down, signals down also? WWV gone? Hmmm. Suspicious.

I'll answer for him, ...No and No.
Receiving loops aren't about signal strength they're about improved Signal
to Noise **Ratio**.

And, receiving loops are about nulling out interfering signals.
Deep nulls has a loop.

Jonesy
--
| Marvin L Jones | jonz | W3DHJ | linux
| Gunnison, Colorado | @ | Jonesy | OS/2 __
| 7,703' -- 2,345m | config.com | DM68mn SK

XC wrote,

I'll answer for him, ...No and No.
Receiving loops aren't about signal strength they're about improved Signal
to Noise **Ratio**.

They are? How do they do that?
73,
Tom Donaly, KA6RUH

On Tue, 13 Jul 2004 10:56:16 -0400, "- XC -" wrote:


"Crazy George" wrote in message
...
William:

Look carefully at what you wrote. Couldn't you have achieved the same
results by turning the RF gain down, or shortening your existing antenna?
Noise down, signals down also? WWV gone? Hmmm. Suspicious.

I'll answer for him, ...No and No.
Receiving loops aren't about signal strength they're about improved Signal
to Noise **Ratio**.
Not hearing 20 MHz WWV at the hours he said he was listening (late eve?)
means nothing as that band folds late at night or propagation simply may not
have been favoring a path between them at that time.
Try some Google-searching for receiving loops, lots of info.

XC



Dumb question: how do you reduce noise without reducing the strength
of the signals you want to hear? How does the antenna know which is
which?

What makes some antennas "quiet."

Bob
k5qwg

A loop has directivity but if the noise is from the same direction as the
desired signal it doesn't help. However if the noise is 90 degrees off then
a loop will help.

--
73
Hank WD5JFR
"Bob Miller" wrote in message
...
On Tue, 13 Jul 2004 10:56:16 -0400, "- XC -" wrote:


"Crazy George" wrote in message
...
William:

Look carefully at what you wrote. Couldn't you have achieved the same
results by turning the RF gain down, or shortening your existing
antenna?
Noise down, signals down also? WWV gone? Hmmm. Suspicious.

I'll answer for him, ...No and No.
Receiving loops aren't about signal strength they're about improved
Signal
to Noise **Ratio**.
Not hearing 20 MHz WWV at the hours he said he was listening (late eve?)
means nothing as that band folds late at night or propagation simply may
not
have been favoring a path between them at that time.
Try some Google-searching for receiving loops, lots of info.

XC



Dumb question: how do you reduce noise without reducing the strength
of the signals you want to hear? How does the antenna know which is
which?

What makes some antennas "quiet."

Bob
k5qwg

OH, for Pete's sake. Loops are sensitive to the H vector. Wires receive
the E vector. Most near field noise tends to be predominantly E field.
But, that seems to only be effective up to 3 or 4 MHz, due to the wavelength
factor, i. e. the near field shrinks as you go higher in frequency. Fully
formed far field wavefronts of noise sources will be just like wanted
signals, and unless some polarization difference is available, then
directivity is the only way to improve S/N. Only in special circumstances
can you see much improvement above 5 MHz due to near field/far field
differentiation.

But, my point was that no improvement in S/N was reported in the original
post. Only a decrease of noise accompanied by a decrease in signal. No
relative comparison offered. Are we supposed to *assume* that the signals
went down due to time of day, while the noise went down because it is a
loop? Maybe the opposite is true? Not enough data to prove either.

--
Crazy George
Remove N O and S P A M imbedded in return address

Bob Miller wrote:
Dumb question: how do you reduce noise without reducing the strength
of the signals you want to hear? How does the antenna know which is
which?

Beams seem to "know" how to receive a signal from one direction while
ignoring noise from the opposite direction. My horizontal dipole seems
to "know" how to ignore vertically polarized noise.
--
73, Cecil http://www.qsl.net/w5dxp



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Cecil wrote,

Bob Miller wrote:
Dumb question: how do you reduce noise without reducing the strength
of the signals you want to hear? How does the antenna know which is
which?

Beams seem to "know" how to receive a signal from one direction while
ignoring noise from the opposite direction. My horizontal dipole seems
to "know" how to ignore vertically polarized noise.
--
73, Cecil http://www.qsl.net/w5dxp



Yes, but does your small, inefficient, shielded loop improve the
signal-to-noise
ratio in the directions of its maximum gain over say, a non shielded loop?
Moreover, how do you get your beam to be less sensitive to noise in its
favored direction? Are you robbing Peter to pay Paul?
73,
Tom Donaly, KA6RUH