Jon, W4ZW....
The OCF dipole you describe is not a lot different than
what RadioWorks sells as a "carolina windom". I had two
160m versions up in Vermont, and am on my second 80m version
since moving south to MD & NJ.
One comment observed that the feedline was coupled into the
antenna, and that your current balun wasn't functioning as a
balun. since it's an unbalanced antenna, I'm sure that's true.
Suggestions:
1) go to the Radioworks.com site and double check the dimensions
of the CW160. As I recall, it was 272' overall, 80 on the short side and
remainder on the other...but I'm unsure about that. duplicate it.
2) The observation that you're seeing a complex impedance being
transformed by the feedline is correct.
You undoubtedly have current on the outside of the feedline, and
will have to use RF chokes to get rid of it. There is a fair body
of work on that topic described on Radioworks website.
The problem is, it's not clear what they use in their topside "balun"
to deal with matching the unbalanced load. It may be a 6:1 or 9:1 balun,
as was described in the QST articles on OCF dipoles by Jack Belgrave, ve2cv
(I think),
some years ago.
Or, you could skip the theory, buy a carolina windom, and get on with life.
Depends on where you find amusement, I guess.
n2ea
jimjarvis@ieee.org
jimjarvis@verizon.net
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