There is a good white paper on the subject of OCF dipoles
on the YCCC website, yccc.org.
160M OCF dipoles will exhibit resonances in all amateur
bands, through 10M, as shown in that paper. Typically,
80M ocf dipoles are useful on the even harmonics only,
80/40/20/10.
My personal experience has been with Carolina Windoms.
I've had several, both 160 and 80m versions. Up and in
the clear, they work well. The 80m 'stealth' version here
is presently around 65', and plays reasonably well.
I experimented with removing the RFC ('line isolator') from
the feedline, and observed that signal levels dropped noticeably
on 30m, 15m and 17m. Whether this was truly due to radiation
from the upper 22' of feedline, or simply a change in the matching
solution, I couldn't tell.
One problem with unbalanced antennas is the need to
get common mode current off the outside of the feedline. More
RF chokes will be required. There is a good article on the
yccc website on that topic, as well.
n2ea
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