Hi Guy,
> I am not as ready as Tom to dismiss the rather broad vertical nulls in
> 20-10m yagi patterns at 60+ feet as a large factor in stack behaviour
> during fades.
Tom me? I didn't mean to imply null filling or movement is not important. I
said (a long time ago) null filling was the advantage of a stack, not gain
improvement.
My point is improved directivity and focusing in the direction of the
signal reduces QSB, not spatial diversity in a fixed phase non-voting
ionospheric circuit.
If you visualize what is happening in the scenario described, you are
really just changing the antenna pattern and getting the signal out of a
pattern null. What we are really doing is creating an antenna with a better
pattern for the application, no matter how we care to look at it. That's
why the effect has no "special name".
> I hear two kinds of stories. One where signals are coming in at a
> certain angle, often rather low, and the other where multiple paths
> are active with different time delay, different incoming angles,
> different incoming directions, and different polarizations.
> As to using the common kinds of BC antennas as a reverse engineering
> inference for what does what in fading...
I actually stole my data from engineering textbooks that blame fading and
selective fading on multipath in ionospheric paths (like page 33-24 of
Jasik's Ant Eng Handbook, the NAB Handbook in various sections, and so on.
73 Tom
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