TopBand: angle vs polarity

[w8ji.tom]

Hi Carl,

 <It is only at sunrise I find the dipoles useful, approaching or even 
> beating a vertical.  The question is WHY are they better.  Is it polarity

> or wave angle?  I suspect wave angle and probably not polarity, but it is

> only a guess.>
> 
> Don’t count out polarization, Tom.  Remember that British IEE paper I 
> sent you?  Although the limiting polarization for those of us in North 
> America is predominantly vertical (which means the polarization exiting 
> the ionosphere going down is predominantly vertical and going up vertical

> polarization couples best into the ionosphere), steep gradients of 
> electron density can cause this predominantly vertically polarized 
> ordinary wave to excite the extraordinary wave, which would be 
> predominantly horizontally polarized.  And of course there are steep 
> gradients of electron density at sunrise.

That's true Carl, but I'm more interested in what I can observe with the
limited antennas I have. Like everyone else, I simply want the best system
I can install at my location with my resources. 

One thing we need to remember is polarity is certainly not either perfectly
vertical or perfectly horizontal, but someplace between even if it has a
trend more towards one polarity or the other.

Another is that near earth, the earth itself "filters" or modifies what we
observe. If the angle is low, the polarity would have to be vertical
because ANY horizontally polarized antenna close to earth has a deep
pattern null in the direction of signal. If the angle was high, most
vertically polarized antennas would have a null in the direction of
arrival. As a matter of fact, it is impossible to have vertical polarity
from straight above! 

I may not be getting the point across, but the point is this. There is
nothing wrong with saying one particular system works better than another
under "X" conditions, but there is plenty wrong with dictating the
mechanics of signal propagation (i.e. wave angle is always X, polarity is
always X) based on VERY
restricted views of what is really happening.  

If we observe something only from one point of view everything we see will
tend to agree with what we observe, and we can form some very incorrect or
incomplete conclusions. For example, imagine we are looking at 20 meters
with an antenna 8 or 15 feet high, and only have eight or fifteen feet of
linear space for antennas and ground systems, and high noise levels. Our
observable would almost certainly indicate everything is a high wave angle,
horizontal, and that propagation was spotty with mostly short openings. 
A guy with a 150 foot tower on 20 meters would have a different opinion.
Only a person with EVERY system could know the true facts.

We fit propagation theories to the antennas we use, rather than knowing
what really is going on. If everyone used dipoles at 60 feet, everyone
would universally observe the band was best at the time when conditions
were most favorable to dipoles at 60 feet. Perhaps the wave angle is under
5 degrees more than 90% of the time, but we would never observe it unless
we had a system that responded to such low angles. 

Since my four square and 3/8 wl vertical are better 90% of the time even at
close distances, I suspect wave angle is a lot lower than credited on 160.
Since the vertical never goes dead (or even falls back by more than an S
unit, whatever that is in dB), I suspect the wave angle is never all that
high at sunrise. Since a 160 ft high dipole never beat the vertical once
but the 260 ft high dipole does, I suspect 90 degrees is far too high a
wave angle for any DX.

73 Tom

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