"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

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.

REALLY? How does it do that?

W4ZCB

Say, for purposes of illustration, that the near field ends at 1 wavelength.
At 2 MHz, that is very roughly 530 feet . At 14 MHz it is about 64 feet.
At 30 MHz, it has shrunk to ~32 feet.

--
Crazy George
Remove N O and S P A M imbedded in return address
"Harold E. Johnson" wrote in message
news:Qf_Ic.82101$Oq2.21575@attbi_s52...


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.

REALLY? How does it do that?

W4ZCB

"Crazy George" wrote in message
...
Say, for purposes of illustration, that the near field ends at 1
wavelength.
At 2 MHz, that is very roughly 530 feet . At 14 MHz it is about 64 feet.
At 30 MHz, it has shrunk to ~32 feet.

-- Why would the near field end at 1 wavelength? It ends
when the wave front arriving at the receiving antenna becomes planar. ie, to
function efficiently in the far field, the receiving antenna needs to
intercept a planar wavefront. That is, the individual rays need to be
arriving in parallel. If the distance between antennas is very great, that
is very nearly the case.

If the capture area of the receiving antenna is great relative to the
distance to the source, the received energy arrives as non parallel rays
that basically reach the receiving antenna out of phase with each other and
partially cancel. So, the gain of antennas measured in the "near field",
where the received energy is not a planar wavefront, will be in error. The
distance to the end of the near field is highly dependent on the gain of the
antenna and with UHF and SHF antennas often exhibiting very high gain, their
near fields can be and often are very large.

The power collected by a receiving antenna within the transmitters near
field is very nearly constant with distance. In the far field, recovered
power varies inversely with the square of the distance.

Regards

W4ZCB

In article ,
says...
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.

True; I didn't report it but it is there. Typically at most
frequencies the desired signal is reduced 1 to 2 S-units with respect to
the whip antenna (strong ones) or my high long wire weaker signal...156
feet AWG 16 up 45 feet fed off center w/ a 4:1 balun) but the noise
level is reduced by anywhere from 3 to 6 S-units...a very! worthwhile
tradeoff. Exact quantitative measurements are not possible on the
Sat800 RCVR because you can't turn off the AGC. My understanding of why
the shielded loop performs this way is that near field noise is
cancelled while far field signal is only attenuated by some factor
relating to capture area. In my temporary rooftop mount I was unable to
easily check out the effect of broadside null.


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