Ron, and all,
I learned: Natural noise (lightning) is vertically polarized because
lightning is a vertical event.
I have seen lots of horizontal lightning, from cloud to cloud, or inside
the same cloud.
Even when I have seen vertical lightning to ground, it has usually
happened simultaneously with horizontal lightning, that brings the
charges to the spot in the cloud where the vertical part starts.
Of course even horizontal lightning noise will arrive at one's place
polarized horizontally, vertically, or anything in between, depending on
the direction of the lightning relative to the direction between one's
place and the lightning. Horizontal lightning aligned with your path to
the lightning generates vertical polarization at your place. Just like a
horizontal dipole antenna operates with vertical polarization at the
directions the wires point.
And then again, any far-away lightning that you hear through ionospheric
propagation will anyway have its polarization thoroughly mixed up.
Man made noise, like noise motor is generally polarized with it's
> feed wiring.
Yes. And that's typically more horizontal than vertical, because power
lines strung horizontally from pole to pole and pole to houses do much
of the radiating. But some vertical power wires exist - just think about
tall buildings - and of course the noise radiated by a horizontal power
line running straight away from your place appears vertically polarized.
In short, I don't think there is much merit to the idea that noise is
most commonly vertically polarized. Neither manmade nor natural noise.
The real reason why vertically polarized antennas acquired a reputation
for being noisy is that many such vertically polarized antennas are
simple monopoles fed against ground. This places them at ground level,
where there is most manmade noise. Also most hams run such antennas
without a common mode choke, thinking that the unbalanced antenna nicely
matches the unbalanced coax cable. So if the grounding is anything but
perfect, the feedline becomes part of the antenna system, and that
feedline runs into the house and right past switching power supplies,
CFLs, power wiring, etc. Put the same vertical antenna high up on a
tower, using an artificial groundplane up there, with a proper
common-mode choke on the feedline, and it will be as quiet as a
horizontal antenna installed at the same place.
Most people can easily do this test using a VHF antenna: Place it
vertically or horizontally, at the same height, and compare. Noise stays
the same. I used switchable polarity Yagis on VHF and UHF for many
years, operating on satellites. I could switch to vertical, horizontal,
left hand circular and right hand circular polarizations. There was no
general noise advantage in either of them. Just the signals, and
specific individual noise sources, got stronger or weaker, depending on
the polarization they had.
On UHF I didn't have much manmade noise, but on VHF I did.
Manfred
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