{"id":1359,"date":"2017-01-30T15:50:50","date_gmt":"2017-01-30T19:50:50","guid":{"rendered":"http:\/\/www.n4rfc.com\/?p=1359"},"modified":"2017-02-05T12:29:55","modified_gmt":"2017-02-05T16:29:55","slug":"k9ay-receiving-loop-antenna","status":"publish","type":"post","link":"https:\/\/www.n4rfc.com\/?p=1359","title":{"rendered":"K9AY Receiving Loop Antenna"},"content":{"rendered":"

I have an acre lot and that sounds like a pretty good size, but actually space for antennas is at a premium. The the house sits fairly far back on the lot and the lot is fairly long and narrow, almost a pie slice shaped, coming to a point in the backyard. Further complicating the issue is\u00a0the arrangement of the trees that make for little room for low band antennas. I was able to squeeze a 40 Meter Double Extended Zepp fed with open wire feeders. Even in an Inverted VEE configuration it goes from lot line to lot line. It does a very good job on most bands, particularly 10 Mhz and below, I generally get pretty good signal reports but the antenna is noisy.<\/p>\n

Non-resonant antennas tend to be noisier than resonant antennas, and dipoles tend to be noisier than loops, at least in my experience. \u00a0This antenna confirms my experience.<\/p>\n

K9AY Loop May Be the Answer<\/h3>\n

I have been looking for a good solution to the noise problem on receive and had heard about the K9AY loop antenna. It is a relatively small receiving loop that works well from 10 Mhz and down. I talked to with several hams about their experiences with the K9AY. N4IQ, Bill, is South Carolina was a great source. He has the K9AY and several beverage receiving antenna and had high praise for the performance of the K9AY.<\/p>\n

When I saw a Array Solutions K9AY loop controller on QRZ’s swap page, I jumped on it. I had the controller in a week and started collecting the other bits and pieces for the loop. I measured off a space in one of the pine straw islands in the back yard. \u00a0I found a good place to put it, but need to get some professional clean up of trees and low limbs. \u00a0After the clean up the XYL was pleased with the \u00a0the yard too. Little did she know what was coming!<\/p>\n

What is a K9AY loop and why did I want one? \u00a0The K9AY is a receiving loop antenna that works well on the lower frequency bands. \u00a0It resembles a Delta Loop, but is a very good directional receiving antenna. \u00a0Comprised of a 85 foot loop with a switching box located at the bottom feed point. \u00a0Below is the basic K9AY Loop. \u00a0You can click on the photos for a larger view:<\/p>\n

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Basic K9AY Loop Configuration<\/p><\/div>\n

The loop is supported at the top, usually by a fiberglass pole, and fed at the bottom. \u00a0One side of the loop is coupled to the feed line with an impedance matching transformer and the other side of the loop is returned to ground through a terminating resistor. \u00a0This makes the loop directional in the direction of the feed line side, somewhat like a Beverage antenna. \u00a0The K9AY now produced by Array Solutions, there are two loops, set at 90 degrees from each other and a control box with relays switches the feed and termination side of the loops.<\/p>\n

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Setting the corners of the loops to the NW, SW, NE, NW directions and using the control box to select the proper feed and terminations gives a 4 directional antenna. \u00a0The relays are controlled by a controller in the shack, that also includes a preamp. \u00a0Since this is a small loop, there is a bit of loss of signal strength. \u00a0The preamp helps bring the signals back up to about the same as a large antenna.<\/p>\n

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Array Solutions K9AY Loop Control<\/p><\/div>\n

My K9AY Loop<\/h3>\n

My implementation was to hang the top of the Loop from rope at strung between two trees in the pine straw island and then tie off the ends to stakes in the ground. \u00a0At the feed point of the antenna there is a relay box. \u00a0The relay box is a waterproof 4 inch electrical box with a plate attached that allows it to be mounted to a round post using a U-Bolt. \u00a0I used a 30 inch section of 1 inch galvanized water pipe driven into the ground for the relay box mount. \u00a0I made a strain relief \/ insulator for the loops out of a piece of 1\/4″ PVC sheet. \u00a0I cut a hole in the center that it would fit over the 1 inch pipe, and used a hose clamp below and a pipe cap on top of the PVC sheet. \u00a0I drilled 4 snug holes in the corners to bring the loop wires through and wrapped them down to the relay box. \u00a0I drove a 8 ft. ground rod beside the mounting post and tied the ground connection to the rod.<\/p>\n

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K9AY Base Detail Photo<\/p><\/div>\n

To hold the top of the loop I made an insulator out of a small piece of PVC pipe with three sets of holes drilled through it. \u00a0The top hole is for the support rope, another pair holes for the SW\/NE loop to go through the insulator, and another pair of holes at 90 degrees from the first set for the NW\/SE loop.<\/p>\n

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Top Insulator Detail<\/p><\/div>\n

Finally, to hold then ends I used simple dog bone antenna insulator tied off to the ground stakes.<\/p>\n

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Dog Bone corner insulator<\/p><\/div>\n

Ok, the ground stakes didn’t work all that well. \u00a0Because the stakes were too close in from the center of the loop, the ends of the loop were too low. \u00a0I just happened to have 4 trees that were off the ends of the loops, so I used some 1\/8 inch rope around the trees at about 36 inches above the ground. That brought up the ends of the loops to a good height. \u00a0It is hard to see, but in this photo looking across a loop, you can see the ends tied off to the trees.<\/p>\n

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Loop End View<\/p><\/div>\n

Not that I was actually trying to hide this antenna, but with the black top rope and the black insulated wire for the loops the stuck back in the trees, the antenna is just about invisible from the yard. \u00a0You can see the insulators and the florescent orange tie ropes for the ends, but otherwise it is very hard to see. \u00a0If you are in a place that you have to hide your antennas, this arrangement will work great for a hidden antenna.<\/p>\n

Results<\/h3>\n

I have had a few days now to work with the antenna. \u00a0I love it! \u00a0For some reason it is very noisy at my QTH. \u00a0This antenna drops the noise level about 15 dB on 40 meters. \u00a0My day for NCS on the Sunrise CW net gives me a good opportunity to evaluate the antenna. \u00a0I can hear stations much better, and using the directionality of the antenna to reduce the noise and QRM I can copy stations much better than with the vertical or my Zepp.<\/p>\n

I find that the loops pattern is a very broad front lobe\u00a0with a very sharp notch off\u00a0the back of the antenna. \u00a0It works better at notching out a signal off the back of the antenna than bringing up a signal off the front. \u00a0However, it still works very well.\u00a0 As you might expect, it doesn’t do much for very strong signals, other than notching them down off the back, but it will bring the noise down and the signal up on weak signals and make them very easy copy.<\/p>\n

It works well on 160 meters through 40 meters, although the preamp in the Array Solution control box passband is about 1.5 to 4.5 Mhz, using it on 40 without the preamp works just fine. \u00a0It also works very well on the AM broadcast band. \u00a0I like listening to AM DX and this antenna works well. \u00a0I have seen several instances when listening on US Clear Channel stations that I can switch the antenna to the SW or SE and completely notch out a US station and hear a Caribbean or Mexican station 599.<\/p>\n

What now?<\/h3>\n

Well, other than wearing out the direction selector switch playing with the antenna, I have read that ground radials under the Loop Array improves the performance. \u00a0So I will be getting some wire and put some radials under the array to see how that affects the performance.<\/p>\n

Update<\/h3>\n

I recorded audio from the FT-1000MP on 40 meters switching between the K9AY loop and the inverted Vee antenna.\u00a0 From the recording you can hear the superior signal to noise ratio on on the K9AY compared to the Vee.\u00a0 The preamp in the Array Solutions control doesn’t cover 40 meters, so the signal strength drops a little, but the Signal to Noise ratio is still superior on the K9AY loop.<\/p>\n\n\t

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