Topband: RE: skewed paths
Tue, 18 Sep 2001 09:56:30 -0400
Hi Milt and all,
First on propagation. Very clearly signals "skew" (to make it clear,
Bill and others call this longpath but I reserve the term longpath for
the "long way around the world" to avoid confusion with between a
skewed short path and a true longpath).
Scattering at the ends of the path makes no sense at all, because
if it was scattering there would have to be dumb luck at both ends
of the path for headings to be skewed into the SAME area of the
The fact both ends beam into the skew obviously means the path
itself is skewed someplace far from the stations at each end, or the
people involved are the luckiest people in the world to have such
weirdly repetitious luck that both ends just happen to bend the
same amount at the same time.
On measuring angle.......
While I appreciate all the interesting comments, the fact is even
with a hundred acres of receiving antennas and years to
experiment, I can't tell you if weak signals are high angle or low
angle or how they get here. I can tell on stronger signals, but only
through years of work and the ability to phase arrays that are
spaced large distances apart...and the ability to select high (~300
feet) dipoles and low dipoles (~50 feet and 150 feet) that are out in
the clear by themselves.
The following are facts we often miss:
1.) A dipole does NOT null vertically polarized signals off the ends.
It nulls them broadside to the dipole. If you want to install a dipole
to null local groundwave noise, it must be broadside to the
noise....not off the end.
2.) When 160 meters is open, noise comes from many directions
at once. You might be unfortunate enough to have a dominant
noise source locally, but in most cases noise that propagates in
sets the S/N ratio. This noise always comes from multiple
directions, although there may be a generally "hot" direction.
3.) A longwire array like a Beverage has many spurious lobes that
are much less attenuated than the null area of a dipole compared
to the main lobe. None of use know in *detail* what the patterns of
our Beverages are, because they are greatly influenced by earth
and what is around the antenna.
If distant signals were at times high angle, I would expect my
verticals to be "dogs" and low horizontals to whip them during
those times. That virtually never occurs. When we have those
"horizontal nights", the high dipole always beats the low
dipoles..leading me to believe the wave angle never gets higher
than ~40 degrees. If it did, the lower dipoles would have stronger
73, Tom W8JI