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Author Topic: Here's a KX-1, Merry Christmas Donald!  (Read 1063 times)
AA4PB
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Posts: 12840




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« on: December 19, 2006, 04:39:54 PM »

A doublet is NOT and end-fed random wire. I would run a couple of radials along the ground, connected to the ground on the radio. Then I'd connect the end of the single wire antenna to the center contact on the radio's BNC connector.

A doublet is a balanced antenna and shouldn't need any counterpoise wires. The doublet should however be fed with a low loss cable like ladder line or perhaps 300 ohm TV twin lead. You'll need a good balun to couple the unbalanced output of the tuner to the balanced feed line. The top section of the doublet should be at least 1/2 wavelength long on the lowest operating frequency.
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AE6RF
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« Reply #1 on: December 20, 2006, 10:30:54 AM »

> A doublet is NOT and end-fed random wire.

Thanks, I'm aware of that. I assumed (incorrectly) that if the tuner was designed for a end-fed random wire, that it should cope with a doublet with a balun.

>I would run a couple of radials along the ground,
>connected to the ground on the radio. Then I'd
>connect the end of the single wire antenna to the
>center contact on the radio's BNC connector.

Pretty much what I did next. The tuner documentation recommends a 24-28' random wire and a 16' "counterpoise." Failing that they recommend a tuned 1/4 wave counterpoise per operating band.

>A doublet is a balanced antenna and shouldn't need
>any counterpoise wires.

I concur. In the spirit of experimentalism I was willing to try it anyway.

>The doublet should however be fed with a low loss
>cable like ladder line or perhaps 300 ohm TV twin
>lead.

I concur, but zip cord is what I had at the moment.

>You'll need a good balun to couple the unbalanced
>output of the tuner to the balanced feed line.

Don't know about "good" or not, but I'm using 13 turns of zip cord bifilar wound on a 35mm film canister. It seems pretty standard practice.

>The top section of the doublet should be at least 1/2
>wavelength long on the lowest operating frequency.

44' is about right for 30m, which it tuned quite nicely. 80m and 40m were bad (9.9) and 20m was about (4).

As the bands recover from last week's solar activity I think my next attempt will be a W3EDP combo.

Will report back with results.

73 de Donald
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