[Antennaware] Dual fed K9AY
k9ay at k9ay.com
Wed May 27 15:25:53 PDT 2009
This is a presentation on arrays of K9AY Loops prepared for the W9DXCC
meeting a couple years back. While working on the article, I put up two
crossed-loop pairs spaced 1/2-wave on 80M. Phasing was 0 degrees broadside,
180 degrees endfire. On 80M, they worked as expected (nice to have no
Although the spacing made the broadside pattern less useful at lower
frequencies, I was surprised at the value of the extra 3 dB signal level
from the combined antennas - the preamp was used much less than with a
A bigger surprise was the value of the side nulls in endfire mode, even at
the low end of the BCB where element spacing was less than 0.1 wave. At
short spacing, the really deep part of the null is quite narrow, but even
off-axis, having some degree of additional rejection off the sides was
obvious to the ear.
Page 6 ("Scenario #2") shows two different arrays built in a corner. With
typical rectangular real estate boundary lines, one or the other might fit a
lot of hams' needs.
> Maybe taking it farther afield, but I have done modeling experiments
> (plus one winter's Europe-only experiments) using two K9AY loops
> end-fire, spaced 135 feet, with 180-degree phasing obtained by simply
> swapping the leads to one input transformer and feeding the two loops
> from a coax tee with equal-length feedlines. The model suggests an
> RDF of 11+, which is a whopping improvement over a single loop and
> gets into Beverage territory. The phasing produces two deep nulls
> perpendicular to the axis of the main lobe, while still maintaining
> useful F/B ratio and reducing the peak takeoff angle to about 23
> degrees. F/B is actually better in the model using less phase shift,
> but I settled for 180 degrees because according to ON4UN at that
> angle no phase errors are introduced by any mismatch.
> The test pair of antennas worked pretty well, but I lacked the
> experience and instrumentation to experimentally verify the
> pattern. I have been noodling over the idea of a 4-loop array, using
> single loops at each end and a classic 4-way loop at the intersection
> in an L pattern of 135 feet per leg. If I can figure out some
> reasonable switching, that should give me NW, NE, SW and SE with 3-db
> bandwidths of about 80 degrees.
> Anyone want the model?
> 73, Pete N4ZR
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