[SECC] K9AY receiving loop--Anyone using one?

[K9AY]

Tad and SECCers,

WX0B at Array Solutions tells me they will have the first shipments of their 
K9AY Loop boxes sometime in October, hopefully before CQWW Phone.

Practical issues with K9AY Loops (and EWEs, flags and pennants) mainly 
involve their location. Since most users have limited space, they often get 
put fairly close to the transmit antenna -- RF overload can be a problem, so 
a "disconnect-while-transmitting" relay may be needed. As Ed noted, coupling 
to the TX antenna can pick up a lot of noise and kill the directional 
pattern -- the same can happen with other towers, aluminum siding, stucco 
with metal mesh underneath, etc.

Most inverted-L antennas get detuned well enough when the T/R relay is 
opened up during receive. Shunt-fed towers and any other tower that is a 
appreciable fraction of 1/4-wave are amost always problems. I once measured 
a 70-foot crankup with a TH-6 and 'shorty forty' and found it resonant at 
about 1750 kHz.

The EWE and K9AY Loop need to be grounded. Since I lived in Lawrenceville 
when the antenna was invented, I would expect a single ground rod to be 
sufficient in most Atlanta-area locations. At my next QTH in Grayson, I had 
0 to 6 feet of clay over granite -- and a lovely 30 by 100 ft. granite ledge 
in my back yard -- and the loop worked fine with a single ground rod.

Finally, I don't recommend Vactrols unless you are only a SWL. Transmit 
power can easily blow out a Vactrol, since the element only has about 1/10 
watt rating. The resistance of Vactrols drifts a lot, too, so you will need 
to constantly adjust them -- it feels like you are "tuning" the antenna, but 
it's a waste of time. A fixed resistor of the proper value (390 or 430 ohms, 
most likely) will give you the proper null -- and keep it there.

The good news is that all you need are some wire, a 9:1 transformer (any 
good Beverage XFMR will do), a 390 or 430 ohm 2-watt resistor, and one or 
two relays to switch one or two loops. Some rigs have a good enough preamp, 
but additional gain is probably needed since signals on the loop are about 
25-30 dB down from your transmit antenna. The extra preamp can be in the 
shack.

Any more questions? I'll be glad to offer my free (and worth every penny of 
it) advice.

73, Gary
K9AY



> Homebrew or commercial.  I'm pretty sure I'm gonna put
> one (actually two loops NE-SW & NW-SE) up before 80
> and 160 get real active again this fall.  I'm planning
> on using a 4 position Yaesu remote antenna switch with
> a couple of additional lines for a Vactrol to control
> the termination resistance.
> Any thoughts or recommendations?  No room for a
> Beverage (antenna that is) or a EWE but the K9AY
> solution should fit fine.  Array Technologies is going
> to re-release the AY Technology system but they aren't
> sure when.
> Thanks in advance.
> Tad, WF4W
>
>
> "What a long, strange trip it's been"
>
> The Grateful Dead
>
> Truckin'