Antenna polarization plays a large role in the success of a long haul DX
contact. As a medium frequency RF signal traverses Earth's magnetic lines of
force in a perpendicular manner on high and mid latitude paths say between
W3 land and SM, higher angle horizontally polarized signals are more readily
absorbed then lower angle vertically polarized signals. On other propagation
paths on the globe opposite results can be found, i.e. horizontally
polarized signals suffer less absorption on a propagation path between VK6
and W6 or S9 and W4.>>>
Maybe, maybe not.
My dipole at 300 feet was no better into VK6 than into VK3 or anywhere else
by any repeatable amount when compared to a good vertical, and I did
hundreds and hundreds of tests. Bob in VK3 is further south than VK6, and
the path is further south also. Why doesn't his dipole beta his vertical, or
my dipole beat my vertical to him?
Southern U.S. QTH's like Florida and New Mexico to S9 may be better via
higher angle horizontally polarized antennas. The N.E. U.S. probably
elliptical polarization via an inverted L. Higher latitudes via a vertical.
Of course though what complicates the matter is that RF often changes
polarization as it's is refracted.>>>
I think that last sentence is the real key.
Even if the ionosphere was a stable perfectly reflecting "sheet of
conductors", it would be pretty tough to maintain a deep cross-polarized
null!
The ionosphere is so unstable and signals scatter so much it would be tough
to reach any conclusion. The ionosphere in the sky is apparently different
than an ionosphere on paper. Radiated power at any wave angle optimum at the
moment also comes in to play, you can't just toss that out.
VK3ZL does V vs. H tests comparing a dipole at 110 feet to a ~45 foot
vertical, and any given day either could be stronger. As a general rule, his
dipole has the highest chance of being stronger only at high solar
disturbances or very near his sunset. Most of the time the vertical is
better. As a matter of fact, he almost never finds the H better except when
propagation is disturbed or at a "sun exposure".
I found the same thing here. At or near my sunrise "peak" my horizontal
antennas all evened out more with verticals. At the same time, the signal is
obviously scattering or multi-pathing because the Beverage and vertical
arrays lose directivity.
A few years back before we started doing tests Bob would have sworn a
vertical was a "dog". That was before he installed a reasonable ground
system. A 45-foot vertical with less than 50 radials isn't a "big" antenna,
yet it beats his dipole most of the time to all areas of the world.
Another factor often ignored is if the polarization is tilted, you would
have to tilt the antenna to MATCH the same tilt angle. A tilt at the
opposite angle would produce a null. Say the tilt looking east is 45
degrees. If the antenna tilted 135 degrees you'd have a perfect null. You'd
better install TWO tilted antennas set 90 degrees apart in tilt if tilt
effects are critical!
Anyone here try to phase two antennas of differing polarization but similar
wave angles to null signals? I have and I can tell you the null changes and
is no longer a null in about 15 seconds or less! A minute later the null can
be a peak. That clearly demonstrates how futile it is to consider a null
from polarization tilt as being "effective" or worrisome over any period of
time.
IMO, describing how to optimize an antenna based on latitude is like
describing how to write sentences in a bowl of alphabet soup.
73 Tom
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