After several winters experimenting with K9AY loops here, I have reached
a few conclusions that others haven't touched on yet. I can't comment
on interaction, because my RX antenna is over 300 feet from my TX antenna.
-- the quality of the ground is quite important. Your marshland
should be pretty good, as long as you have a good connection to it. Try
laying down a few 50-foot radials in addition to your ground stake.
-- the feedline *must* be decoupled for common mode currents, or else
pickup on the shield may negate the directivity of the loop itself. I
have had very good luck with the ON4UN center-tapped bead choke
described on the Contesting Compendium at
<http://wiki.contesting.com/index.php/Common_mode_chokes>.
-- the best indicator of whether the K9AY is "working" is the signal to
noise ratio. Since the rear null is so narrow, you won't often hear big
differences in signal strength when you switch directions, but for
signals that are anywhere in the "front 180 degrees", you should hear a
significant improvement in the SNR. I just don't think there is any way
that your vertically-polarized loop should be able to compete as a
receiving antenna.
-- The rear null is pretty "selective" not only in direction but in
arrival angle. This could be the reason that you get seemingly good
directivity on the ground weave from a local station but not on skywave
signals. You might try finding a broadcast signal on the high end of
the band and a few hundred miles away, and checking the directivity on
that signal. The K9AY loop is much beloved by MW DXers because of the
deep and narrow null, which allows them to listen for weak signals on
the same frequency as stronger ones.
73, Pete N4ZR
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On 8/29/2009 5:40 AM, Doug Turnbull wrote:
> Scott and Jerry,
> I am most interested in this thread so thank you for starting it.
> Scott, I find that my Array Solutions K9AY gives me about a 6 to 15 db
> directivity between front and back. Some signals show little directivity
> difference while with others changing the direction is most noticeable. My
> antenna has proven invaluable in contests to null Europe and listen to the
> States on 160M. I also find it useful to listen on 80M and find the same
> relative front to back ratio.
>
> I have never found much difference in adjusting the terminating
> resistance.
>
> I have a friend, who is a first class 160M operator and EU pioneer on
> this band, GW3YDX who has never been able to get satisfactory performance
> from his K9AY so I suppose performance is variable but in my case the
> antenna is most useful.
>
> 73 Doug EI2CN
>
>
>
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