[TenTec] Not TT - Wire antenna question

[Stuart Rohre]

W3DCG and group,
If you have a "Windom" type antenna, then there is no "balun" in the world
that will balance what is inherently an unbalanced antenna (doublet) set up.
Consider that one leg is shorter than the other leg of the antenna.   That
means each side has a differing impedance to the feedline.  There are
unequal currents in the antenna legs.

A balun is a balanced to unbalanced converter.  It MUST have an equal sided
antenna to work with on the balanced side, and then it allows use of
unbalanced line like coax on the other side.

What you are seeking is an LC network that will force equal currents into
both sides of the Windom.  No such animal has been common in the ham
literature, although probably one could be designed.  What might work
better, is just a cable choke type solution to keep the unbalance current
off the outside of a coax feeder.  Either beads or coiled coax can choke RF.
There is a big misconception among amateurs that a balun magically can
correct all unbalanced to balanced situations.  But again, this is
inherently an unbalanced  situation.

In the case of the Windom, you inherently will have some residual unbalance
in the doublet, and thus you have an un-un situation, unbalanced to
unbalanced.   Typically, this is NOT what the built in 4:1 balun of a
transmatch is designed to handle.  Now, it might be possible to use
sufficiently long feeder that the effect of unbalanced currents is minimized
and still tune the antenna and feeder with the usual transmatch.

Remember, the true Windom was a single wire feed antenna.   Any balancing of
the antenna currents involved accepting radiation off the single wire
vertical feeder.  So called windoms fed with coax or parallel lines are a
different animal, where usually you do not want radiation off the line.

As a practical matter, studies by L. B. Cebik, W4RNL, have shown only 10 per
cent imbalance for the parallel line currents in the balanced feeder of an
end fed Zepp doublet.  This implies if you accept some feed line radiation,
you probably could feed the Windom as well without a balun and just go to
the built in balun of the transmatch with acceptable results if the feedline
length is used as a transformer to bring the match within the range of the
tuned circuits.

Would hate anyone buying an expensive commercial balun for the wrong
application.
73
Stuart
K5KVH