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Re: [TowerTalk] K9AY loops-- phased

To: K4SAV <>, Joe Szeliga <>,"Tom McAlee" <>
Subject: Re: [TowerTalk] K9AY loops-- phased
From: Terry Conboy <>
Date: Wed, 20 Dec 2006 10:12:01 -0800
List-post: <>
I've followed with interest the discussion about phased arrays of 
K9AYs vs. 4 squares, such as the DX Engineering receiving array.  I 
decided to model a few variations, and they back up K4SAV's & NI1N's 
comments pretty well.  As the basis for performance comparison, I 
used the RDF (receiving directivity factor) employed by W8JI.  Here 
are the results:

Antenna         RDF, dB
Whip                    4.7
K9AY                    7.3
EWE                     7.4

4Sq Whips 90*   10.1
4Sq K9AY 90*    10.2
4Sq EWE 90*     10.2

4Sq Whips 120*  11.6
4Sq K9AY 120*   11.4
4Sq EWE 120*    11.4

1 wl Echelon-Bev        11.5
1.5 wl Beverage 11.6

[The 4 squares all use 1/4 wl spacing.  The 120 degree phasing system 
is very close to what results from using the crossfire phasing scheme 
recommended by W8JI and DX Engineering at that spacing.  The 
crossfire system is broadband and can be used over several bands, and 
the current phases will vary accordingly.]

The bottom line is that a single K9AY or EWE (which are essentially 
equivalent if properly installed) is a better receiving antenna than 
a single whip vertical, but using them in arrays may be much more 
complex than required for good low noise receiving performance.  The 
only notable improvement for the arrays of EWEs or K9AYs is a 
reduction in the off-axis back lobes, which could be useful for 
attenuation of some low angle QRM.  On the other hand, as K4SAV 
describes, the array of verticals has a null at zenith, which could 
help attenuate lightning static and NVIS QRM.

It's also interesting that all of the 4 Square arrays are very 
similar in performance to a 1.5 wavelength Beverage or an echelon of 
1 wavelength Beverages (staggered by 0.186 wl) with 135 degree 
phasing (although the back- and side-lobe structure is different.)

Incidentally, models of the DX Engineering array actually show 
slightly better RDF (a few tenths of a dB) at closer spacings than 
1/4 wl (with appropriate phasing).  I suspect the arrays of EWEs and 
K9AYs would be similar.

73, Terry N6RY


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