2004 KØS, Kurt N. Sterba Strange Antenna Challenge

Operated by Erik nØew and Dwayne wb5plj,

Chicken Wire Delta Loop

25-Feet of Chicken Wire, Delta Loop Configuration, Bottom Fed
Icom-706MKiiG, 100-Watts, MFJ-962D & MFJ-969 Versa Tuners, Battery Power
May 29, 2004

   Dwayne and I were operating the K0S Special Event Station. There were a number of other stations operating K0S "Contest" Stations too. In 2003 enough interest was generated that shortly before this year's special event we discovered a few other stations also wanted to play with strange antennas. We hadn't anticipated this but we quickly threw together a "contest" of sorts.

   This was the first Strange Antenna we used in the 2004 Kurt N. Sterba Strange Antenna Challenge.

   This "antenna" is difficult to make out in the digital pictures we took. It appears almost as smoke in many of the shots. It will be the most difficult Strange Antenna from which to make a good looking certificate because it is so difficult for the camera to distinguish.

   This roll of chicken wire was deployed as the Chicken Wire Delta Loop. It measures 25-feet in length and 4-feet wide (this is the same roll of chicken wire later used to make the chicken wire semi-vertical). I tied two rope loops about six-feet from each end and ran another length of rope through these loops. Each of these longer ropes were then suspended from a nearby tree branch. The height at the top was about 8-feet above the earth and the bottom was about 5-feet above the earth. The bottom is where the antenna was fed.

   This image shows Dwayne wb5plj calling CQ as I stand atop the step ladder which I used to tie the supporting ropes in the nearby trees, and shows a close up of the Altoid's Mint can "breakout" box. It has a SO-239 mounted to it along with a 5-way binding post (purchased from a local Radio Shack store). The coax is terminated into the S0-239 as with any normal antenna connection. Inside the Altoid's can is a short piece of # 12 wire connecting the center conductor of the coax to the red binding post, and another short length of wire connects the coax shielding to the black binding post via the SO-239. The entire metal can is connected to the coax shield just as takes place with a standard transmatch (antenna tuner) or your transceiver.

   The next image shows a close up of how each short length of # 12 stranded wire (blue in color) is attached to the chicken wire. A plastic "dog bone" insulator (white) is hose clamped to the chicken wire. The blue # 12 wire is sandwiched between the dog bone and the chicken wire. The hose clamp is hand tightened to secure the electrical connection between the blue wire and the chicken wire. The pink ribbon is a short length of marking tape I purchased at the local Lowe's home center. It is there to make the chicken wire more visible. I often tie short one- or two-foot streamers such as this to guy wires, antennas, ladder line, or anything else that a person may inadvertently walk into when I operate portable. It is just to provide a little safety edge for myself and others as they walk around my portable station set up. The last thing you want is someone to accidently come into contact with your antenna elements, or supporting equipment while you are operating! It is cheap "insurance" to be sure!

   In this image you can see both of the dog bone / breakout wire connection points. The yellow rope leads down to a mailbox and post that is there to provide some weight to hold down the end of the chicken wire loop. Left to its own devices it will naturally try to reclaim its natural shape. In other words, the two ends try to roll up towards the middle of the wire. This helps keep the triangular shape of a delta loop.

   This antenna was operated until noon and we made seven contacts ranging from California and the state of Washington, to Michigan, to Louisiana. The stations we worked were using both beams and inverted-vee antennas in standard configurations, most of whom were using 100-watts. All of these contacts took place on 20-meters.

   Along the left side of the page you can see a silhouette of the chicken wire delta loop. This is one of the images in which the chicken wire is actually visible. I found this to be a pretty good antenna all things considered, and were I seeking a make shift antenna to press into service I would certainly consider on of these. Obtaining a longer roll of chicken wire might make for a better antenna and if I can find such a roll I will attempt to use it next year. We were a little bit concerned that the roll may in fact have been too wide (too wide-banded) and thereby have such a wide bandwidth that many "trash" frequencies would be picked up by the receiver. This, however, seemed to be an unfounded concern. We did NOT find we were picking up too much trash (such as AM/FM broadcast, or shortwave, stations).

   Using the MFJ-962D Versa Tuner III we were easily able to achieve a successful tune with very little trouble. This tuner is rated at 1.5 KW, and the interior variable capacitors are much larger than those found in my MFJ-969 transmatch. The roller inductors appeared to be identical. Both the 962D and 969 tuners were used on this antenna.

Please note of the little gray boxes adjacent to the 5:1 SWR line. These indicate the approximate location of the amateur radio bands from 160- to 6-meters. This allows us to gain an impression of how each antenna shapes up across the entire HF range in which our amateur radio bands reside.

   The final image shows the SWR chart of the chicken wire delta loop. (Blanks of this chart, and others, are available in my "K0S Field Manual" (free download, with provisions, the 2nd Edition of which will soon be available).) There was approximately a 15:1 SWR on this antenna at 20-meters, which was close to its maximum SWR. From there it drops to about 5:1 SWR for 10- through 6-meters.

   The notes at the very bottom of the SWR chart show the SWR, series resistance (Rs) and series reactance (Xs) at two 20-meter frequencies. As you can see, the resistance was a little on the low side (13-Ohms) and the reactance was a tad on the high side (right around 110-Ohms). Still, well within the range of both the MFJ-962D and MFJ-969 transmatches to tune.

   I was quite pleased with the 962D tuner. This was the first time I tried using it with "strange" antennas. Last year I used my MFJ-969 exclusively. Dwayne had recently purchased the 962 (used) so we were eager to test it out. There were occasions when my 969 was unable to tune up an antenna while his 962 did tuned up the antenna in question. This is not to say I may not have been able to tune up my 969 by altering the feed points (where the hose clamps were attached) and this was not the case with the chicken wire delta loop (again, we used both tuners with this delta loop).

   I started calling CQ on 28.500 MHz (10-meters) for about 15 minutes but when I spun though the band I couldn't hear anyone out there so I assume the 10-meter band was dead. This seemed to be the case during the entire weekend. This was expected based on the propagation report put out in the ARRL's email to which I subscribe. According to that report 17-meters was the highest frequency range that was expected to sustain HF operations, and I found this to be true, although I did hear a couple people talking about brief openings on 6-meters. However we didn't operate on 6-meters during any of these short windows of opportunity, although we did call CQ on both 10- and 6-meters throughout the weekend.