[Antennas] Rotary Joints for Ladder Line

Sun, 28 Apr 2002 11:52:35 -0400

I have never heard of this kind of system.  I wonder if anybody has such an old
handbook and can make a copy for me.  I will pay copy and mailing costs or fax
costs.

73, Joe

Karl Kanalz wrote:

> The ARRL "Handbook" (older editions, say prior to 1950) had construction
> projects for a three-element
> 20M beam, mounted on a "stub tower" on top of a house roof (made of wood!)
> and using a "rotary joint" for open-wire feedline.
>
> Essentially, it was two large loops of copper tubing - one mounted (fixed)
> on the tower (with insulators, of course), and the other coupled *just above
> it* on the rotating part of the antenna mast assembly.  As the antenna was
> rotated, r.f. energy was coupled from the (fixed) lower "loop" (about 12
> inches in diameter as I recall) to the upper (moveable) loop which then fed
> the driven element (balanced feed) of the Yagi.
>
> The loops were un-tuned, too, so it should work for a tri-band system such
> as your KT-34
>
> -----Original Message-----
> From: [email protected]
> Sent: Saturday, April 27, 2002 10:17 AM
> To: Pat W
> Cc: [email protected]
> Subject: Re: [Antennas] VSWR on Log Periodic.
>
> Wow!
>
> No problem on transmit, just crank up the power, but that is a pretty
> heavy hit on the recieved signal.
>
> Guess I will stick with my KT-34.  It is very close to 1:1 on all three
> bands at the antenna.
>
> Or does someone have a good design for a rotary joint for use with
> ladder line?
>
> Thanks Pat,
> Frank Kamp
> K5DKZ
>
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