With respect to the Cebik article:
I agree that this is excellent information. However there is not much
discussion about feedline current balance, and the effect of the ground
being much closer to one end of the antenna than the other. The only
reason given for the ten foot height above ground of the bottom end of
the antenna, was for safety, keeping the high voltage at the end away
from people. Surely the greater capacitance to ground of the lower end
of the antenna is going to have some effect on the current balance, and
the currents in the two wires of the feeder will not be equal and
opposite. While I doubt it's a problem, that is where this discussion
started, as someone claimed excessive radiation from open wire feeder.
Feedlines with equal and opposite RF currents in their two conductors
(either open wire or coax) don't radiate. Getting the currents to be
equal and opposite requires care. In the absence of nearby objects, it
would seem to me easier to accomplish this with a horizontal dipole.
Orienting the dipole vertically seems like a way to guarantee that the
currents will not be equal.
Then again, how often are we luck enough to be able to put up a
horizontal dipole that does not have one leg closer to a tin roofed
building or metal pole or tower than the other leg.
None of this would keep me from building whichever version, vertical or
horizontal, fits the space available. I have always found ways to
mitigate RF in the shack problems. I don't transmit on TV channel
frequencies (at least not at a significant power level) so if my
radiating feedline makes someones TV set have problems, I guess there is
a problem with the TV.
DE N6KB
Anyone interested in more information about vertical dipoles should
take a look at what Cebik has to say. As always, he has excellent
information that is accurate and to the point:
http://www.cebik.com/gp/v20.html
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