Ken Fowler wrote:
On 7-Apr-2004, David Ryeburn wrote:


The Windom single-wire feedline radiates by design.
It would be extremely difficult to keep the OCF
feedline from radiating but a 50:300 current balun
at the feedpoint might help.

Here's a relatively simple way to keep an off-center fed "Windom"
antenna feedline from radiating: Install another Windom antenna of
identical dimensions at an acute or right angle to the existing one. Tie
the long side of the second Windom to the short side of the first one,
and vice versa. Feed the thing with a balanced line, or with coax
through a balun. I don't have EZNEC (it won't run on Macs) so I don't
know what the pattern would be like, but if everything was symmetrical
the feedline ought not radiate.

David, ex W8EZE

--
David Ryeburn

To send e-mail, use "ca" instead of "caz".


I modeled the above with EZNEC using two perpendicular one-half wave elements one-quarter wave above
ground at 7.2 Mhz. Each half-wave was divided at a point one-sixth wave from the end The short end
on each side of the feedpoint was connected to the long end of the perpendicular wire. The source
was placed on a 2 inch wire between the two short-long pairs. I included a wire to ground from one
side of the feed point to show shield current.

At 7.2 Mhz, the feedpoint impedance was 59 - j157. I didn't attempt any element adjustments to make
it resonant. The far-field pattern approaches omni-directional with 7.7 dbi at an elevation of 60
deg. The wire from feedpoint to ground shows very little current.

At 14.3 Mhz, the feedpoint impedance is 37 + j138. The far-field pattern is bi-directional with 11
dbi at an elevaton of 30 deg. The wire from feedpoint to ground shows current similar to the
element current.

So it appears to me that the feedline may not radiate on some frequency but definitely will radiate
on others.

Ken Fowler, KO6NO

I think David might have been *very* tongue in cheek in his comment,
Ken. Sounds like his suggestion is saying "If you want a windom to not
radiate on the feedline, you turn it into a dipole." 8^)

- Mike KB3EIA -