TopBand: angle vs polarity

[Carl K9LA]

Tom W8JI said

<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.

I’m not saying this is the why the dipole is stronger at sunrise - it’s 
just a possibility that needs some good controlled observational data to 
prove or disprove (perhaps using a vertical over salt water, a vertical 
over average ground, a low horizontal dipole, and a high horizontal 
dipole - one hell of an experiment indeed).  Maybe it is angle.  I don’t 
know.  But I do know that there are some pretty interesting things 
happening at 1.8MHz due to the Earth’s magnetic field that usually can be 
ignored on the higher HF bands.  This interaction of the Earth's 
magnetic field with 1.8MHz energy results in interesting things 
happening with the refractive index and with polarization (and 
absorption).

And another thing that clouds the issue - many of our antennas have a 
response to the other polarization.  For example, Beverages respond to 
horizontal polarization off the side.  This certainly doesn't help clear 
up matters.

Carl K9LA

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