[TowerTalk] Horizontal + Vertical Polarization Question

[Jim Lux]

Interesting writeup, however, I'm not too sure about your statement:
"In as much as a the receiving station benefits from diversity receiving antennas, the transmitting station reciprocally benefits in providing a more diverse signal to the receiving station. "

For the following reasons:
1) Ionospheric paths are not reciprocal (Faraday rotation being but one aspect)
2) On transmit, the goal is to get as much power radiated in the right direction as possible. Since losses in ground reflections are a significant effect, and highly polarization sensitive, one is probably best off transmitting in the polarization that minimizes losses, bearing in mind that the ionosphere will randomize the polarization on the way to the receiver.
3) On receive, the goal is to get a signal which is above the received noise floor.  For this, CP or a diversity receiver are probably the best bet, since they minimize the maximum depth of a cross polarization null, and hence improve the probability that the received signal will be above the noise.  For what it's worth, if what you want to do is merely guarantee that the maximum null is, say, 10 dB, the diversity antenna can be a lot lower gain (i.e. it can be an omni) than the primary antenna, and in fact, probably should deliberately be lower gain (so you don't wind up building an "adding interferometer).  This is only true on HF, by the way, because a higher gain antenna gets more of the desired signal, but also gets more atmospheric noise.  VHF and higher, higher gain antennas are better, because the noise is in the receiver.

(I maintain that the real value of a gain antenna, on receive, is that it allows you to remove interference, rather than increase the received signal power.  That interference might be atmospheric noise, which is not uniform (thunderstorms and the like are localized phenomena))




----- Original Message ----- 
From: "GEORGE PRITCHARD" <ab2kc at optonline.net>
To: "Richard Karlquist" <richard at karlquist.com>; <RLVZ at aol.com>; <towertalk at contesting.com>
Sent: Saturday, November 22, 2003 3:59 PM
Subject: Re: [TowerTalk] Horizontal + Vertical Polarization Question


> Gentlemen,
> I am using circular polarization on TEN meters, using a 4 element quad.
> Loops acting as parisitic elements "don't care" about polarity, with NO
> polarization attenuation. That's another reason that quads rule. QSB caused
> by polarity rotations are not isolated by the typical high "vertical to
> horizontal isolation" that the parisitic elements on yagis have. In quads...
> only the driven element attenuates the opposite polarity. For more info on
> the topic of QSB fading with respect to: "Faraday rotations in the
> ionesphere" , please go to the attached link, See my quad (and my son) and
> click on "ARTICAL".  http://www.amwindow.org/pix/htm/ab2kc/ab2kc5.htm
> George AB2KC
> 
> ----- Original Message ----- 
> From: "Richard Karlquist" <richard at karlquist.com>
> To: <RLVZ at aol.com>; <towertalk at contesting.com>
> Sent: Thursday, November 20, 2003 10:27 PM
> Subject: RE: [TowerTalk] Horizontal + Vertical Polarization Question
> 
> 
> > > Has anyone experimented with feeding both a horizontally polarized and
> > > vertically polarized antenna simultaneously on HF?  Such as,
> > > feeding a horizontally
> > > polarized yagi and a  vertical on 20, 15, or 10 meters?
> >
> > I haven't done that, but I have done a fair amount of A/B'ing
> > of a 20 meter ground mounted vertical vs an inverted vee at 60
> > feet.  More often than not, one is better than the other,
> > but it's equally likely to be either one.  If you could
> > feed both without destructive interference (and that
> > assumption is by no means assured), then you would get
> > a diversity effect and reduce QSB.
> >
> > I have also A/B'ed 2 verticals 800 feet apart and QSB
> > on them is different (one may be up while the other is
> > down, etc).
> >
> > Hope that helps.
> >
> > Rick N6RK
> > _______________________________________________
> >
> > See: http://www.mscomputer.com  for "Self Supporting Towers", "Wireless
> Weather Stations", and lot's more.  Call Toll Free, 1-800-333-9041 with any
> questions and ask for Sherman, W2FLA.
> >
> > _______________________________________________
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> > http://lists.contesting.com/mailman/listinfo/towertalk
> >
> 
> 
> _______________________________________________
> 
> See: http://www.mscomputer.com  for "Self Supporting Towers", "Wireless Weather Stations", and lot's more.  Call Toll Free, 1-800-333-9041 with any questions and ask for Sherman, W2FLA.
> 
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