The Legend of W7DND's "Magic Antenna" or "DND Array" #hamr

He had a FANTASTIC signal! One I will never forget.   -N4RV

I thought that might get your attention! What is that thing, you ask? That's Tom Erdmann, W7DND (SK) homebrew 40M/20M Magic Antennas. It was a "killer antenna" to say the least.

Anyone remember him? I think we'd all enjoy hearing some audio or seeing old pictures of W7DND. Please share with us!

He hand-built a vertical-yagi beam on a rotating dock (a rotating dock!) on salt water, with an arguably perfect parabolic bay facing North to South on the East Side... creating a Worldwide Legend, many would say he was the loudest thing out of W7 for many years. "He would work stuff I couldn't hear with my 3EL 40M Yagi!" says one W7 DXer.

Tom lived a few homes north of my Family's beach house in W7. Since the youngster years, I tinkered with wires and poles along, and literally in that very same beach. The signals are truly awesome and in comparing them to the Yagi I had at 50' there, often times the vertical sitting on the water's edge would hear things that just were not there on the Yagi.

We aren't promoting rotating docks (yet!) but we are offering a useful, and we think the smarter solution (see the performance data vs. other antennas on the market) for many restricted space QTH's. The DX Flagpole and Greyline Performance Vertical-Dipoles inspire the customers we talk to every day, to tell us amazing 'stories of legend' similar to Tom's story above. Stories from guys who have operated and in some cases built engineering marvels! Many of these folks are retiring to HOA regions for better weather and propagation but they are also finding the HOA restrictions don't allow much in the way of antenna farming. It's our hope the DX Flagpole makes it possible for Hams to return to the airwaves with confidence.

Whether you know someone retiring, downsizing, or maybe a new ham looking for a versatile antenna that performs with confidence, have them take a look at our DX Flagpole and of course our non-stealth, non-flag options, the Greyline Vertical-Dipole line.

At Greyline Performance, we're an RF Research Group, an Antenna Company, and hams just like you. We can be found staying up until 2 AM at Dayton talking radio theory and radio adventures. We hope you find our current and forthcoming products and services useful too. Thank you. 

Please check out our Flagpole selection and just maybe you know someone that could enjoy getting back ON THE AIR. Please share our website with them. They will be glad you did.

Hey, one more thing. Check out our Ad on the DX-World website:

Let's get our friends ON THE AIR! Pass it on...

73, Greyline Performance


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  • An important thing about verticals on the beach: they can sometimes engage propagation modes that cannot be engaged by horizontal antennas at attainable heights. properly site vertical array, by salt water, can radiate down to about one degree; that can often send your signal far enough out on the launch to get into a gray-line area of the ionosphere where there is an F-layer tilt, and that can launch chordal-hop propagation, whereby signals do not return to the ground after each refraction; instead, they skid along the bottom of the F layer three or more times, eventually reaching another area where the F-layer is tilted, at which point the signals return to earth. But each ground reflection that is avoided saves about 16 dB of loss, which obviously can be the difference between a station being S9. . .or inaudible! There were several times, at W7RM, where we could hear and work Europe all day, because the ultra-low-angle launch, in November, sent our signal into gray-line area, and thence via chordal hop propagation into Europe. We startled many a European at their mid-day as we called in, when no other North American stations were being heard in Europe.

    The DND Arrays were truly game-changers.

    Chip Margelli K7JA
  • The original DND array was the basis of the spectacular 40- and 80-meter arrays we used at W7RM in the early 1970s. One 40-meter array was on JA, and the other on Europe, and indeed there were many situations where the DNDs would hear Europe 3-4 hours before the 3-element horizontal Yagi at 400’ off the water atop the bluff. The DNDs also had the 210’ bluff in back of them, yielding every bit of 60 dB of F/B, making it possible for us to hear on the low end of 40 without stateside QRM (!). If a pin dropped in Tokyo on 40, we heard it.

    Chip Margelli K7JA

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