Original DEWD

The antenna consists of two equal parallel wires shifted a little bit w.r.t. each other. The parallel wires are connected together with a short perpendicular wire with a feed point in its center. See the DEWD geometry and dimensions in the drawing below.

Find below the original SWR plot as published by UR0GT on the CQHAM.RU Forum. Click here to go to his original post.

As you can see, the DEWD ensures very low SWR over the whole 80 m band. The antenna was modeled with copper wires of diameter 2 mm.

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It is possible to re-design DEWD to cover the 75/80 m band (3.5-4.0 MHz). L.B. Cebik, W4RNL (SK), did it and presented the dimensions in chapter 12 of the "Antennas: Wideband & Broadband, Volume 2" (published by antenneX Online Magazine). 

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I simulated both designs and that's what I got. The original UR0GT 3.5-3.8 MHz DEWD goes first.

The DEWD gain in free space was 1.77~1.8 dBi what is a split decibel below a dipole. That's a very small penalty one need to pay for so perfect SWR plot.

The plot of the W4RNL version for the 3.5-4.0 MHz range looked like that:

Although I used exactly the same dimensions as L.B. Cebik provided in his article, I got a slight shift towards the higher frequencies. About 10 kHz or so. That happened probably due to different segmentation we used. Anyway, the change was so small, I did not care to fine tune the dimensions to reproduce W4RNL's results. The gain varied from 1.74 through 1.81 dBi over the 3.5-4.0 MHz range.

The radiation patterns of both version were essentially the same as that of a regular dipole, and there was almost no difference if you oriented the antenna in horizontal or vertical plane (< 0.05 dB difference in gain). Of course, the orientation in horizontal plane will create lower wind load.

A shorter version of the DEWD (for the 3.5-3.8 MHz range) also designed by UR0GT has its longer arms folded back as shown below.

Its SWR plot is presented below.

Such a  folded-back DEWD version is shorter than the basic version by 3.36 m at the price of only insignificantly bigger SWR and lower gain (1.72-1.76 dBi). The antenna was modeled as made with copper wires of diameter 2 mm.

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DEWC Dual-Element Wideband Cobweb

One of the antennas suffering from narrow bandwidth is a broken square loop. You may know this antenna in its multi-band version as the Cobweb. I modified the loop using the DEWD concept and that's what I got.

I compared SWR plots of the DEWC and a classic single wire Cobweb for 20 m band (broken square loop 2.6 x 2.6 m). 

As you can see, the improvement in SWR is indisputable. At the same time, the DEWC radiation pattern did not get worse but even slightly improved.

It is probably not possible to create a 5-band version of DEWC. I tried but failed. The interaction between the elements for different bands was too strong. I also tried a relay switched version, but it did not work for me either. 

Anyway, even as a single band antenna, the DEWC should be considered as an interesting quasi-omnidirectional antenna with horizontal polarization. It is smaller than a turnstile. A 40 m band DEWC should be still feasible, not to mention the higher bands. 

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DEWQ Dual-Element Wideband Quad Loop

If you take a square loop one wavelength long in circumference, there is really no big need to improve its bandwidth. But I wanted to check if the UR0GT concept could be applied also to the square loops. I chose 14 MHz for modeling the quad. The regular single quad loop for this band, if made with Cu wires of diameter 2 mm, should have dimensions 5.58 x 5.58 m and should be driven with a 112.5 ohms source. 

The DEWQ looks like in the drawing below and needs a 50 ohm source.

Note that the upper "shorting link" is not in the center of the top wires but is shifted to the side by 0.6 m. Very similar results can you get if you shift both upper and lower links to the same side by 0.3 m. The SWR plots of a regular quad loop and DEWQ are shown below. 

If you compare the bandwidth for SWR<1.5, the DEWQ has a noticeable advantage. Its radiation pattern is very slightly skewed due to lack of perfect symmetry, but it is negligible (couple of degrees). DEWQ gain is reduced by 0.3 dB if compared with a single wire quad loop.

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The next logical step was to check if the dual element can improve something in the 2-element Cubical Quad. I modeled it but did not find anything interesting. Its performance was very close to the traditional Cubical Quad. 

A similar thing happened with a 2-ele Yagi - it did not benefit from UR0GT's idea.