Owen Duffy wrote:
Fred McKenzie wrote in news:fmmck-9C2AC4.14313718032007
@nntp.aioe.org:

In article ,
Richard Clark wrote:

...
Someone asked that if the OCF Dipole was so good, why didn't everyone
use one? When I got my start back in the 50s, everyone did use one. I
used my "Full Windom" for several years on 80/75/40/10 CW and AM. In

Fred, I think the term "OCF Dipole" is usually used today to mean a
dipole fed with coax and balun (often 4:1, usually not 1:1) fed offset
from the centre and often operated at half wave resonance or harmonic
multiples.

That would be the type that I'm talking about. I've used them and like
them. For some reason I see them as a nice compromise antenna, and
Richard doesn't. Or maybe I'm talking about this type, and Richard is
speaking of the other, "classic" Windom. But then again, I'm way out of
me league here!


...
Using the modeling software, is there a feed-point where impedance is
close to an available balanced feed-line on multiple bands? As close,
I would accept a 2:1 SWR.

If you are going to use an ATU and open wire line (as distinct from
balanced line) why are you restricting the max VSWR to 2. Practical open
wire lines can operate at much higher VSWR with acceptable losses.

Once you have addressed that question, then ask yourself why you wouldn't
just feed such a dipole in the centre and reduce the common mode current
problem caused by the asymmetric feed.

A dipole of more than about 35% wavelength at its lowest operating
frequency, centre fed with practical open wire line and a good ATU will
allow multiband operation with efficiency should be acceptable as part of
the multiband compromise. For an example, look at Fig 10 in the article
http://www.vk1od.net/G5RV/index.htm . Although the article is about the
G5RV, Fig 10 is just a 100' dipole, centre fed with classic tuned feeder
and ATU.

That is pretty much exactly what I am using now, and it works a charm.
It's a fine antenna, if a little tight to match on 75/80 meters.

- 73 de Mike KB3EIA -