[TowerTalk] TowerTalk Digest, Vol 172, Issue 38
hhoyt at mebtel.net
Thu Apr 27 10:31:26 EDT 2017
I have used OCF dipoles for years, and as a "one-antenna for all bands"
they do work. I use the "Carolina Windom" and for those unfamiliar with
it, the Carolina Windom uses a (relatively) short vertical radiator
between the feedline and the horizontal feed point in addition to the
two unequal length horizontal radiators, and is fed with coax.
I have a few caveats regarding the use of this type of antenna:
1) The horizontal feed point transformer and line isolator are only good
to several hundred watts CW or SSB despite their claims of 1500 watts.
On CW I can see the SWR rise on a long transmit cycle at 500W at certain
2) In order to truly isolate the feedline, additional common-mode
choking is absolutely required, both immediately at the supplied
isolator and where the feedline transitions into the structure. Without
these three CM chokes, I had severe CM currents on the feedline and RFI
in the house.
3) The use of a tuner is not optional, given the wide impedance swings
through the multiple resonances. This can be a daunting issue if one
has to manually retune every time you change bands or even frequency,
and I initially spent way too much time with a manual ATU (Drake
MN-2000) before changing my setup to an Elecraft KAT500 with a
K3/KPA500. This newer combination memorizes settings by frequency and
then automatically retunes with frequency changes which is far easier.
Some people who model antennas decry the Carolina Windom's odd patterns
due to the interaction of the various horizontal and vertical
components. Having used a resonant center-fed dipole in the exact
location the OCF now occupies, I will tell you that "odd" pattern helps
fill in directional nulls the dipole had and gives me much more
omni-directional capabilities than did the dipole, of course at the
expense of maximum main lobe gain. However, if you have one antenna and
it is non-rotatable, this is an advantage, not a disadvantage.
A single wire antenna will seldom be an optimal antenna on every band,
but my experience says the Carolina Windom is a decent compromise, I
have even won several 160M contests at the 100W level, and regularly
break pileups in AF and EU with 500W. Performance is best on lower
bands 160-40M, this being said I have even logged over 100 countries on 10M.
Does this antenna even come close to the performance of a Yagi on
40-10M? Hardly, but if I had a tower and Yagis (I'm working on it) I
might still consider this OCF for 160-80M transmit use. A well-worn
saying comes to mind when discussing this antenna with others: "the
perfect is the enemy of the good" and we can't all have antenna farms...
Just my $0.02 worth of actual experience...
Howie - WA4PSC
On Wed, Apr 26, 2017 11:01 PM Pete Smith N4ZR wrote:
> If you could have one horizontal single-wire antenna for 80-10 meters,
> what would it be?
> Tuner and open-wire line are possible if necessary.
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