[Top] [All Lists]

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

Subject: Re: [TowerTalk] rotatable k9ay and more...
From: K4SAV <>
Date: Sun, 08 Jan 2006 19:36:18 -0600
List-post: <>
If your purpose is to try and null out a specific signal, then rotating 
the loop may have some merit.  If your purpose is to obtain better 
signal to noise ratio, then I think rotating the loop is wasted effort.

The null for the K9AY loop is narrow, and you can tune it to minimum by 
adjusting the termination resistor. The shape of the antenna, height 
above ground, and the ground characteristics will determine this 
resistor value. This null is also first thing to go when conditions 
change. The maximum value of this null does not effect the signal to 
noise ratio very much. If you have a specific signal to reject or there 
is a noise source coming from only one direction, and that noise source 
is the dominate noise for the band, then placing it in the null may 
improve reception.  This is not the way most people use this antenna.

Most of the time, noise sources come from multiple directions 
simultaneously. If you are interested in improving the signal to noise 
ratio under these conditions, then you need to narrow the receive lobe 
for the loop. The K9AY loop does give improved signal to noise ratio by 
virtue or rejecting some signals to the rear, but the loop has a very 
broad pattern, both in the azimuth and elevation. There is still a lot 
of gain in the straight-up direction, which you don't need for receiving 
purposes. You will find it difficult to improve this pattern very much 
by changing the shape of the loop. Making it a little smaller will 
improve the pattern somewhat at the expense of lower gain. Take a look 
at the pendant, flag, and EWE antennas.  All of these and the K9AY work 
on the same principle, but use different shapes, and the performance for 
all of them is fairly close. Also if you are really only interested the 
amount of the null, you can get a more pronounced null using the 
pendant. If you want to make any significant improvement in signal to 
noise ratio, you will have to start looking at using multiple elements.  
All of these antennas can be used in multi-element configurations.  If 
you start doing this, it is possible to produce a pattern better than 
anything you can achieve with a single beverage, although it will be 
considerably more complex than a beverage. A good compromise is two 
elements for NS, and two elements for EW, and you can pick any of these 
types to use.

There are also other types of receive antenna to choose from. You might 
want to stop by Tom's web site. He has lots of tabulated data on receive 

Jerry, K4SAV wrote:

>Hi All
>Here I come again on (unanswered) question about rotatable k9ay loop
>I've never considered this antenna before since I was not really
>interested in topband 'til now (after 14 years of hamradio....hmm).
>So I'm picking up some info about on internet.
>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.....
>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 ???
>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/funcioning ???
>Thanks, Federico
>TowerTalk mailing list

TowerTalk mailing list

<Prev in Thread] Current Thread [Next in Thread>