Hi,

I am trying to figure out the proper balun to use on an Off Center Fed
dipole I am going to construct. I have settled on a 6:1 UnUn design
by Jerry Sevick, W2FMI. My question is will this properly prevent
feedline radition? Is some feedline radiation always expected /
inherit in this type of antenna design?

-Scott, WU2X

On Tue, 27 Nov 2007 08:57:40 -0800 (PST), wrote:

My question is will this properly prevent
feedline radition?

Hi Scott,

The long answer: No.

Is some feedline radiation always expected /
inherit in this type of antenna design?

The short answer: Yah, sure, youbetcha!

The answer you need: Stick with the UnUn, and add a choke directly
beneath it. Then add another choke a quarterwave beyond that, and
possibly a third one a quarterwave further along. That should do it
for this exceptionally (notoriously) unbalanced design.

73's
Richard Clark, KB7QHC

Hah, ok that will be tough because it will be used on most HF bands.
But I think I have the solution. I will cover the coax from the
antenna feedpoint to the rig with #73 beads. That ought to do it

-Scott, WU2X

On Nov 27, 12:18 pm, Richard Clark wrote:
Then add another choke a quarterwave beyond that, and
possibly a third one a quarterwave further along.

On Tue, 27 Nov 2007 10:05:03 -0800 (PST), wrote:

Hah, ok that will be tough because it will be used on most HF bands.
But I think I have the solution. I will cover the coax from the
antenna feedpoint to the rig with #73 beads. That ought to do it

Hi Scott,

That is another solution, certainly, and one I have used as well.
Actually I used 40 or 50 beads spread along a 20' section of line with
that line section closest to the feedpoint.

73's
Richard Clark, KB7QHC

I am trying to figure out the proper balun to use on an Off Center Fed
dipole I am going to construct. I have settled on a 6:1 UnUn design
by Jerry Sevick, W2FMI. My question is will this properly prevent
feedline radition? Is some feedline radiation always expected /
inherit in this type of antenna design?
=======================
In the past I have used an off-centre dipole with wire lengths ratio 1:2
(Windom) It had a 1:4 balun meant to transform the impedance from 50
to 200 Ohms. It worked quite well on the harmonic bands 80-40-20-10 m
The balun was obviously located at the dipole Tee.

Where would you locate a 1:6 unun ? I am eager to learn.
I also have Jerry Sevick's book :'Building and Using Baluns and Ununs'.
It is a treasure.

Frank GM0CSZ / KN6WH

On Nov 27, 1:53 pm, Highland Ham
wrote:
Where would you locate a 1:6 unun ? I am eager to learn.
I also have Jerry Sevick's book :'Building and Using Baluns and Ununs'.
It is a treasure.

The balun I am going to use is the one from the book "Transmission
Line Transformers, Fourth Edition" Section 8.2.2: 50:300-Ù Unun.
http://www.cwsbytemark.com/ sells it 69.95$, which is pretty fair
considering it comes in an alum. enclosure. I have the Buckmaster
commercial OCF ($$$$$) and I have never really been too happy with it.
I want to build myself a new version and also I have a bunch of people
I am trying to get started in the hobby and in my opinion, this is a
good starter antenna for HF.

-Scott, WU2X

wrote:
I am trying to figure out the proper balun to use on an Off Center Fed
dipole I am going to construct. I have settled on a 6:1 UnUn design
by Jerry Sevick, W2FMI. My question is will this properly prevent
feedline radition? Is some feedline radiation always expected /
inherit in this type of antenna design?

The two different legs of the OCF dipole have different
impedances so it is virtually impossible to balance both
the voltages and currents into each element. If you install
a choke about 22 feet down the coax from the feedpoint, you
will have duplicated the Carolina Windom which takes
advantage of the inherent feedline radiation.
--
73, Cecil http://www.w5dxp.com