Tag: 160m

Thanks to a interesting article about the so called Half Extended Double Zepp (HEDZ) by W5DXP we managed to get our EDZ working om both 80m and 160m. The antenna is working fine now on 80m. I couldn’t test in on 160m yet, because my own rig (IC-730) doesn’t work on that band, but the measurements with the MiniVNA show a acceptable SWR between 1800 and 2000 kHz. When breaking up we will do some physical measurements to see what the exact size of the dipole and feeder is. The (H)EDZ is also a little bit lifted now, the center is 12 meters above the ground, the endpoints 8 meters.

We also erected the remaining antennas: the 1/4 wave vertical for 40m, and the HyGain AV-12AVQ for 10/15/20m. In the upcoming weeks we will extend the number of radials for the 40m vertical.

Setting up antennas on a corn field is not really easy. Ok, there’s no corn in the winter, but the field is very wet and muddy. When the temperature drops below zero, the field becomes icy, and above zero the amount of mud under your (wooden) shoes grows with every step.

In 2009 we built an extended double zepp (EDZ) for 80m, which also performed really nice on 160m. Although the antenna performed well in the past contests, it was always a big trouble to match it. After lots of experiments and measurements, we finally found an unexpected relation between the length of the feeder and the “resonance” frequency. Ok, this antenna is not resonant on the desired working frequency, it only provides a workable impedance and very well radiation at some point. I always thought that this point was merely depending on the length of the dipole, and that the length of the transmission line merely influenced the impedance. Well, not for the EDZ! It is a non-resonant antenna, and all sizes do matter! So this makes the antenna a bit more complex, compared to a simple halfwave dipole.

We found some websites stating that the length of the feeder line should be about 48 degrees, so 48/360 wavelength. We want to have a 80m EDZ, center frequency at 3700kHz (= 81.08 meters), so the length of the feeder line will be 81.08 x 48 / 360 = 10.81 meters. This is not a practical length, since the shack is not right beneath the antenna. So we add 1/2 wavelength feedline, resulting in a total length of 10.81 + (81.08 / 2) = 51.35 meters.

Setting up the EDZ took quite some time. We had to options: the weekend of 4/5 December, or the weekend of 11/12 December. The first weekend would be freezing cold, the second weekend really wet. Since the cornfield is almost inaccessible when really wet, we decided to go for the first weekend. With the snow hitting in our face, ice hidden below the fresh snow, and a really cold wind, we managed to set up the EDZ. But due to the bad weather and ground surface conditions it took us lots of time, so we did not manage to get the feeder in the correct length. Two weeks later, the dipole came down due to the large amount of ice. So there is still some work to do on the EDZ…..