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Re: [TowerTalk] rotatable k9ay and more...

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Subject: Re: [TowerTalk] rotatable k9ay and more...
From: "Michael Tope" <>
Date: Sun, 8 Jan 2006 13:56:09 -0800
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> I've understood that a single loop has a sharp null on loop plane and only
> in one direction (splitting loop terminals we have opposite direction
> null) and it has to be peaked adjusting Rterm.
> With classic "two loops" configuration we have 4 deep nulls available
> (i.e. N,E,S,W)
> Several articles claim antenna to be 360 degrees elctrically rotatable.
> What they intend ??? I see a cardioid pattern which,yes, I can rotate ,
> but in only 4 position.....

That is correct, Frederico

> First time I was thinking that null control was able to rotate somewhat
> cardioid pattern making two loops to interact but I was wrong....
> That's why my question : if i've got to null out a signal coming 45
> degrees from loops plane (from my previous example a NE, NW, SE or SW
> interfering signal) what is antenna behaviour ?? What settings operator
> must use ???

I have never tried this, but in principle you should be able to
connect the two perpendicular loops in parallel a move the null
to the line 45 degree line that bisector the angle between the planes
of the two loops. The efficiency of the array would probably be lower
because the effective spacing between the front and rear vertical
components of the loops would be closer than in the case where
the null lines up with the plane of one loop (the K9AY loop is in
essence a pair of short phased verticals). The optimum termination
would probably be different as well. With a proper controller, you
could set up two loops to place the null in 8 different directions (
45 degree increments) instead of just 4 (90 degree increments).
This might be a worthwhile thing as the main benefit of the K9AY
loop comes when you are able to point the relatively narrow null
towards a dominant noise or QRM source.

> So I came to idea that a single k9ay loop with fixed connections (but
> still adjustable Rterm) can be mechanically rotated with a normal light
> duty rotator to place null exactly where we need.
> Will be this solution useful/functioning ???

Yes, I think so. I would also equip the rotatable loop with a relay so
you could still switch between forward/reverse directions instantly.
This could prove helpful when adjusting the termination resistor value
for maximum front-to-back.

73, Mike W4EF........................ 


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