[50mhz] Ground gain vs antenna polarization

[bonddaleena at aol.com]

VERY interesting discussion! I remember back in the early 70s (living in the worst possible location in Central Mass.), working my first MS.
Radio was a HW-101 I built with a Hallicrafter HA-6, 5 element ant on top of the apartment building. WOW! I thought I had a wonderful station. ha ha

I mention this only because a common station I worked was K9LEE (I hope that's right). I think he had stacked beams, with one 'twisting' into a vertical configuration at the 1st DE.

I could be mistaken, but although that was MANY beers ago, it always struck me as unique, and have never heard of anyone else using that same setup...... That was WAY before computer modeling, etc.

ron
N4UE






-----Original Message-----
From: Paul Kelley N1BUG <paul.kelley.n1bug at gmail.com>
To: w7gj <w7gj at q.com>
Cc: 50mhz <50mhz at mailman.qth.net>
Sent: Mon, Jun 27, 2011 5:04 pm
Subject: Re: [50mhz] Ground gain vs antenna polarization


Hi Lance,
Thanks for that information. I recall reading somewhere long ago 
bout reduced ground gain with vertical polarization but couldn't 
ecall any details. I have no idea where I read it. It may have been 
he same study you mentioned. I'm afraid I have forgotten much from 
y EME days!
I think part of the situation with antennas of different heights on 
errestrial modes is the angle of signal arrival. Since the peaks 
nd nulls in the vertical pattern vary with antenna height due to 
round reflections, it seems plausible one might have a signal in a 
ull on a high antenna but in a peak for a lower antenna - or vice 
ersa. But polarization may very well play a role, as you suggest.
Years ago I noticed a very pronounced "flutter" on meteor scatter 
ignals at 144 MHz. It wasn't until many years later, running 
SK441, that I clearly saw the rapid fading during longer bursts. It 
ould be very interesting to know the cause. Perhaps it would be 
nlightening to do some meteor scatter with circular polarized 
ntennas and see if the fading is still evident.
73,
aul N1BUG

On 6/27/2011 3:15 PM, Lance Collister, W7GJ wrote:
 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
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