Doublets I Have Known and Loved

In a recent post, I covered some (very) basic information about the venerable doublet antenna. This time around, I’ll cover some practical examples. These are antennas I have used and one unique design I know of.

Doublet Fed with TV Twinlead

My go-to portable antenna for several years was a simple doublet fed with 25 feet of that cheap, brown TV twin-lead. For the radiating elements, I used some #22 stranded hookup wire.

I first built the antenna as a 40M dipole fed with RG-174 coax. After a while, I wanted to cover multiple bands, so I removed the coax and replaced it with the twin-lead. I used a small piece of fiberglass perf board for the center insulator.

I have often used my homebrew Z-match tuner to load it up, although a 4:1 balun and a short run of coax to my rig’s internal tuner works fine, too. The whole antenna weighs next to nothing, and fits in a sandwich-sized Ziplock® bag.

Nothing fancy but it works great.

This is the center connector for my 66-foot doublet. The feedline is the old, cheap TV twin-lead.
This is the center connector for my 66-foot doublet. The feedline is the old, cheap TV twin-lead.

Up and Outer

The Up and Outer is simply a doublet with one vertical leg and one horizontal leg. I had done some experimenting with this old-time antenna and decided to build one to use while on vacation in the Outer Banks of North Carolina. 

I planned to support the vertical leg with a 28-foot Jackite pole, so I made a simple modification to a 44-foot doublet I had on the shelf. I spliced 6 feet of additional wire to each of the elements down to 28 feet each, and I was in business. Like my 40M doublet, the Up and Outer is fed with TV twin-lead and uses a perf board center insulator.

This antenna always goes with me on our annual Outer Banks vacation. I’ve used it from numerous beach rental houses, and it’s perfect for use on a second story deck. I used it last summer with great results, connecting it directly to my KX3. And, if I need to, I can use it as a normal horizontal doublet.

Appalachian Trail (AT) Dipole

This design is the brainchild of my friend, Ed Breneiser WA3WSJ, and goes back about 20 years. Rich Arland K7SZ, wrote about it in his QRP column in QST [1] back in 2001 and devoted a few pages to it in one of his books [2].

In simplest terms, it’s a 40M doublet made from #26 copper-clad stealth wire. Ed used a 3/4-inch PVC end cap for the center insulator (see photo). After soldering wires to an SO-239 socket and routing the wires through the end cap, the inside of the end cap is potted with epoxy. This makes it pretty much bomb-proof. 

The antenna is fed with 300-ohm ladder line, which is soldered to a PL-259 UHF connector. The PL-259 probably causes a slight imbalance, but in the field, you’ll never notice it. You can also feed it with coax and use it as a normal 40M dipole. Pretty cool, huh? 

When I built mine, I went with some #22 stranded hookup wire I had on hand. Although I departed from Ed’s design a bit, this doublet has been a reliable portable antenna over the years. 

My version of the WA3WSJ AT Dipole. The discoloration on the PVC end cap is from a mishap I had while potting it with epoxy. On the right is a PL-259 connector used with 300-ohm ladder line. As you can probably tell, this antenna has seen years of heavy use.
My version of the WA3WSJ AT Dipole. The discoloration on the PVC end cap is from a mishap I had while potting it with epoxy. On the right is a PL-259 connector used with 300-ohm ladder line. As you can probably tell, this antenna has seen years of heavy use.

WV0H Park Doublet

Myron WV0H designed a unique doublet that he dubbed The WVØH Park Portable DoubletHe uses two 50-foot pieces of wire to create a 60-foot doublet fed with a built-in open-wire feeder. I won’t attempt to offer a detailed description here; Myron’s blog post provides all the details you need to build one. Go check it out.

While I’ve never used Myron’s unique antenna, I can vouch that it works. I worked Myron a few years back while he was out in a park with his doublet. I can attest that it puts out a great QRP signal.

Wrap-Up

Well, that’s about it. If you need a reliable, easy-to-build, multi-band antenna, give the time-tested doublet a try.

73, Craig WB3GCK

References:
[1] Arland, R. (2001, July). QRP Power – Antenna Time. QST, p. 100.
[2] Arland, Richard K7SZ, Low Power Communication – The Art and Science of QRP, The American Radio Relay League, 2nd Edition, 2004, Chapter 6, pp. 6-36, 6-37

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