About Us

September 6th 03, 05:58 AM

(Richard Harrison) wrote in message ...
Dale, W4OP wrote:
"Could you give an explanation of why this is?"

Joe O. had written:
"A Horizontal Loop will pickup less vertically polarized atmospheric
noise."

Than a vertically polarized antenna, yes.

ON4UN wrote on page 10-7 of "Low-Band DXing":
"The loop will act as any horizontally polarized antenna over real
ground; its wave angle will depend on the height of the antenna over the
ground."

I tend to agree with this statement.

So, the short answer is "cross-polarization".

The dipole is horizontal also. Or I would assume anyway if hung from
two trees.

Most noise is local and reaches a receiver through ground-wave
propagation. Horizontally polarized waves have zero ground-wave
propagation. Their low-angle reflections are out-of-phase with the
direct wave.

Horzontal antennas are in general quieter than vertical antennas.
Cross-polarization loss has been often reported as about 20 db.

Loops, small in terms of wavelength, tend to have the same volts and
amps induced into all their increments. This helps reduce sensitivity to
overloads from high-power signals at frequencies far below the desired
reception, as might be received on a voltage-probe antenna.

A "sky wire" loop, as usually thought of, is not a small loop though.
Thats a name given to the practice of feeding a loop on all bands,
with the loop usually a full wave or larger for the lowest band to be
used. Kind of the loop equal to feeding a 1/2 wave low band dipole on
all bands with ladder line...
As far as noise, if the dipole and loop are both horizontal, there
should be little if any difference in noise received, unless the
pattern of the particular antenna favors the noise source. I haven't
done extensive tests, but it's my opinion that the common perception
of large loops being quieter than large dipoles is wishful thinking.
I've never noticed any real difference. It's always been my experience
that if a certain antenna receives less noise than another, not
counting any local noise ingress problems, it's inferior in the
direction of the noise received than the other. "All the same polarity
and the noise in the far field"
Noise is rf same as any other. All good antennas pick up a lot of
noise, if there is noise to be picked up. If I have an antenna thats
"too" quiet, I start to worry..:/ As far as the original poster... I
don't think changing antennas is worth the hassle just for SWL use.
Maybe not even if he transmitted. I guess would depend on the
particular band to be used. The patterns will be different on the
various higher bands, but I doubt different enough to make or break
things with most signals. If he's not hearing a certain station on the
dipole, he probably wouldn't on the loop either. MK

Thread Tools	Search this Thread
Show Printable Version	Search this Thread: Advanced Search
Display Modes
Switch to Linear Mode Switch to Hybrid Mode Threaded Mode

Similar Threads
Thread	Thread Starter	Forum	Replies	Last Post
Distance to Link Coupling in a Loop Antenna	Al	Antenna	6	October 28th 03 12:02 AM
SWL tuning an MFJ loop?	Hatfield	Antenna	3	July 25th 03 11:44 PM
Snap-on choke hurts shielded loop	Loopfan	Antenna	3	July 14th 03 08:30 PM
Feedpoint impedence / wire diameter	Tom Bruhns	Antenna	0	July 10th 03 08:23 PM

Menu

About Us