[SECC] K9AY Loops

[Paul Pescitelli]

I too after visiting Hal last summer built more than one of these...

This year I have tried something different. I put up a beverage. I
know many of you are saying, but I don't have room...... mine is only
200ft long (the depth of the property) and it works like gang busters
on 20-80M, not tried much on 160 just yet.

I use the same binocular core that W8JI and Hal use and run some rg6
to the DX Engineering preamp and am very happy... Worked the 3b7c on
30-80 using it..  Now I will make it reversible.

Try it, you WILL like it.. either solution that is... some receive
antenna is better than none.

Paul K4UJ


On 10/5/07, Bill Coleman <aa4lr at arrl.net> wrote:
>
> On Oct 2, 2007, at 4:27 PM, Hal Kennedy wrote:
> > Its interesting how some subjects that have been around a while
> > sometimes suddenly pop up and become 'in vogue."  NN4ZZ and K4DLI
> > have just added K9AY loops for receive, and three different groups
> > and/or individuals have been over to my QTH in the last two weeks
> > to inspect mine.
> >
> > As far as I'm concerned, you can't get a better bargain than a K9AY
> > if you don't have room for beverages.  They are thirty feet in
> > diameter and 25 feet high and they do work.
>
> Hal, you can add me to the list of folks who have recently put up a
> K9AY. Last year, grabbed some spare parts and put up a single half-
> sized loop. Last month, I added a second loop and added relay switching.
>
> Our own Gary, K9AY, was extremely helpful with this project. The
> standard design uses 85-foot loops and requires a 25-foot high
> support. Gary indicated that shorter loops would work as well. I had
> a 44-foot piece of wire available, so I hooked it up and it worked
> great.
>
> Gary's original loops were around 110 feet long, which were too long
> for 80m. My half-size design works pretty well on 80 and 40m, but it
> a bit short on 160m, so signal levels are pretty low there (about 35
> dB down from the vertical).
>
> My support is an oak tree -- passing over a branch about 10 feet
> high. The wires are spread out by draping over the outer branches.
> Ground connection is two counterpoise wires about 10 feet long right
> under the antennas.
> > You can buy the one from Array Solutions for significant bux or you
> > can build your own for around $10.  Mine is home brew.
> Me, too. It's interesting to put an antenna analyzer on the loop. The
> SWR is flat from 160m up to nearly 30m with a termination resistance
> of 390 ohms (in my case).
>
> I built my loop almost entirely from the junk box. I think the only
> thing that was bought was some stainless hardware for connecting the
> wires.
> >   Gary does not recommend decoupling beads on the feedline, but I
> > believe they are a useful precaution to keep common mode current
> > off the shield.
> I pretty much followed Gary's original relay switching design, except
> for the matching transformer. Gary used a trifilar-wound 9:1
> autotransformer. Following some tips on the hard-core-dx.com site, I
> opted for a magnetically-coupled 9:1 transformer instead, with the
> windings separated as much as possible.
>
> I used three stacked FT37-43 toroids with 8 turns in the primary and
> 24 in the secondary, separated as much as possible on the cores.
> After putting an antenna analyzer on the loop, I ended up pulling one
> turn off the secondary for better match. The FT37-43 toroids are
> pretty small, but they were in the junkbox. Something like an FT80 or
> FT114 would work better, and you wouldn't need three of them.
>
> The magnetically-coupled transformer allows you to electrically
> separate the antenna ground from the feedline sheild, which reduces
> the chance of any coupled noise. Decoupling beads should be unnecessary.
> > It's worthwhile reading.  I have spare cores if folks want to wind
> > transformers – it takes 5 minutes to make one.  I use 2 turns and 6
> > turns, Gary uses 3 turns and 9 turns but our results are the same.
> > Ill be adding a second K9AY soon and phase them with an MFJ noise
> > canceller.  Can't work 'em if you can't hear 'em.
> W8JI has some interesting information on the K9AY loops here:
> http://www.w8ji.com/receiving.htm
>
> By Tom's analysis the K9AY Loops have a higher figure of merit than
> either the EWE / Pennant, and are just about 1 dB less than a one
> wavelength Beverage.
>
> So, if you don't have room for a Beverage, the K9AY seems like your
> best bet to improve your receiving antenna.
>
> I know that my loops made the difference between working 3B7C on 80
> and 40m and not working them at all. They were in the noise on my
> transmitting antenna, but copyable on the loops.
>
>
>
> Bill Coleman, AA4LR, PP-ASEL        Mail: aa4lr at arrl.net
> Quote: "Not within a thousand years will man ever fly!"
>              -- Wilbur Wright, 1901
>
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