[50mhz] Ground gain vs antenna polarization

[Lance Collister, W7GJ]

Hi Paul,

I recall reading something from Europe about a study that showed vertically polarized 
signals with ideal ground gain were about 3 dB less than horizontally polarized 
signals.  I also made a number of contacts with NL7Z on 6m EME when he was using his 
pair of 6 element side by side yagis, vertically polarized.  It was apparent that the 
main lobe of that array was higher than would have been expected for a horizontally 
polarized array.

Which leads me to wonder about the difference in signal strength between incoming 
signals of different polarities, if an antenna's best reception of the different 
polarities is at different elevations.  Many people on 6m make remarks such as "he 
was Q5 on the lower antenna but I couldn't hear him at all on the higher antenna".

I have been told that polarity makes no difference on ionospheric propagation because 
the signal is scattered into all polarities.  However, I wonder whether some of what 
people are actually perceiving as differences in elevation of ground gain lobes 
between different height and gain antennas might also be due to differences in 
polarity between incoming signals.  Unfortunately, there are not many of us with huge 
rotating towers who could easily mount antennas of different polarities and switch 
between them.  If that were the case, the innovative receiver from HB9DRI might be a 
very interesting way to automatically maximize the incoming signals:

http://www.linkrf.ch/

I have recently begun using FSK441 to collect rare gridsquares out west, and was 
immediately struck by the very pronounced 1 second fading that is clearly displayed 
on the SpecJT waterfall when longer bursts are received.  I don't know what is 
causing this rapid very regular QSB, but the first thing that came to mind was 
Faraday rotation.  The signal traces basically look like someone dipped a paint 
roller partially in a pan of paint, and then rolled it across the computer screen!  I 
think it would be very interesting if someone did some research to determine if the 
signals are in fact peaking up in the opposite polarity during the nulls during such 
a meteor burst.  I think it would also be very interesting to learn whether there is 
in fact a large difference in signal strength between "ionospherically propagated" 6m 
signals of difference polarities.

Paul, I apologize if all this has already been discussed and covered somewhere.  I am 
just a student of this Magic Band, and find these anecdotal observations very 
intriguing.  GL and VY 73, Lance


On 6/27/2011 4:33 PM, Paul Kelley N1BUG wrote:
> I have been reading comments about ground gain in a recent thread.
> Meanwhile I am trying to remember what I once knew about ground gain
> vs. antenna polarization. Could someone refresh my memory? What
> affect does using vertical polarization have on ground gain, if any?
>
> Thanks&  73,
> Paul N1BUG
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-- 
Lance Collister, W7GJ
(ex WA3GPL, WA1JXN, WA1JXN/C6A, ZF2OC/ZF8, E51SIX, 3D2LR, 5W0GJ)
P.O. Box 73
Frenchtown, MT   59834-0073
USA
TEL: (406) 626-5728
QTH: DN27ub
URL: http://www.bigskyspaces.com/w7gj
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2m DXCC #11/6m DXCC #815

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