[TowerTalk] A Question of GAIN

w8ji.tom w8ji.tom@MCIONE.com
Tue, 20 Oct 1998 11:46:44 -0400

Hi John,

> But I can't agree with the dual polarity issue where you state that
> it will always increase fading.  The deepest fading is when linear
> polarization 
> is rotating and there is NOTHING to get signal that is crossed polarized.
> This has been shown by using circular polarization for receiving linearly
> polarized signals that are rotating as a way of reducing fading.

We'll have to disagree on that one John.

If you have the time and inclination, we'll talk about it. But I'm in some
pretty good company on this one.
> I think this may help to explain the issue that keeps coming up about
> quads having less fading than Yagis.  While both are linearly polarized,
> the Yagi has a number of additional polarization "filters" called
> that
> may increase the rejection of orthogonal signals. 

 Whereas the quad has
> directors that are not polarized (closed loops).  When added to the fact
> the quad has vertical wires in the driven element and the currents may
> not be perfectly balanced to cancel any vertical signal (due to no balun
> or a poor balun) then the quad may reject vertical signals less than the
> Yagi resulting in less fading for vertically polarized signals.

Ditto. All less than perfect current balance does is broaden the pattern
and skew the pattern into an elliptical polarity that is slightly off
horizontal. Statistically, it is more likely to have fades because the
pattern is slightly less directive.   

Quads, however, are like religion. They have followers and hard-core
believers. I don't argue religion.
Facts do not support many of the claims.

73 Tom

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