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The World Radio SD-20 Dipole is made from a pair of SD-20 fishing poles. They are supported by a PVC Tee in the middle. They can support up to a 40' dipole, or even a 44' dipole by hanging a couple of feet from each end.
To make one, obtain two SD-20 poles and a 1" Compression Repair PVC Tee. The Tees are available with a couple of choices of connection type on the center leg, I chose 1" slip solvent cement size, so a 1" pipe or equivalent fitting will cement into that. The other choice is a 1" pipe thread. Either will work, choose whatever makes the mounting to your pole the easiest. For those with Buddipole masts a 1" to 1/2" FIP threaded insert can be used. (Note that this antenna is a bit heavy for a Buddipole mast, use with care and always guy it).
Support Mast
The mast will need to be sturdy enough to support a 5 pound antenna. If the mast is conductive the window feedline should be routed 8" or more away from it.
I have not tested this yet, but a push-up aluminum flagpole might be just the right strength and convenience for this antenna.
It would not be hard to use 4 SD-20 poles and a boom to make a 2 element beam! It this case the elements would be tuned to resonance, plus or minus as appropriate for a director or reflector design.
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The World Radio SD-20 Dipole is made from a pair of SD-20 fishing poles. They are supported by a PVC Tee in the middle. They can support a 40' dipole, or even a 44' dipole by hanging a couple of feet from each end.
To make one, obtain two SD-20 poles and a 1" Compression Repair PVC Tee. The Tees are available with a couple of choices of connection type on the center leg, I chose 1" slip solvent cement pipe size, so a 1" pipe or fitting will cement into that.
It would not be hard to use 4 SD-20 poles and a boom to make a 2 element beam!
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- www.plumbingwarehouse.com PVC tee
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SD-20 Beam
It would not be hard to use 4 SD-20 poles and a boom to make a 2 element beam!
World Radio SD-20 Dipole
World Radio Magazine used to sell SD-20 20 foot telescoping fiberglass fishing poles, and a version of this antenna. Theirs was set for 20 meters, as I recall, but here I cover a multiband tuner version of the antenna. They no longer sell the kit or the poles, but the parts are readily available.
The World Radio SD-20 Dipole is made from a pair of SD-20 fishing poles. They are supported by a PVC Tee in the middle. They can support a 40' dipole, or even a 44' dipole by hanging a couple of feet from each end.
To make one, obtain two SD-20 poles and a 1" Compression Repair PVC Tee. The Tees are available with a couple of choices of connection type on the center leg, I chose 1" slip solvent cement pipe size, so a 1" pipe or fitting will cement into that.
Parts Sources
- www.plumbingwarehouse.com PVC tee
- National Sport Supply SD-20 Poles
Remove the ring/bottom cap at the bottom of the SD-20 poles. This can be done by carefully hacksawing the ring but don't nick the pole. If you don't cut all the way through you can force off the ring without cutting the pole.
The pole bases will now fit into the Compression Tee. First put the PVC nut/ring on, then the rubber seal. Slide the pole halfway into the tee and tighten up the PVC rings on both poles.
Adapt the other leg of the tee to fit your vertical support.
To support a wire, spiral it around the pole to support it. Tape the wire to a 2" long piece of 1/4" polyethylene tubing. Slide this over the tip section to hold the wire without needing to tie to the tip of the pole.
In the center use a lightweight insulator to support the wires and the twinlead or ladder line. A piece of PC board can work well.
And there you have it.
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AlanB, wb6zqz