[Antennas] Rotary Joints for Ladder Line

[Karl Kanalz]

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: fkamp@attbi.com
Sent: Saturday, April 27, 2002 10:17 AM
To: Pat W
Cc: antennas@mailman.qth.net
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