[Elecraft] Coax-Fed Antenna for KX1 with ATU

[Stuart Rohre]

I would expect any OCF antenna, of which the Carolina Windom is an example;
to have more problems tuning than the G5RV.   I have in hand the original
1929 QST piece on the Windom antenna, which was not developed by Windom, (he
was only the scribe he says); but was team work from Ohio State Univ.  It
maybe should be the OSU antenna.

It is emphasized that it only works on its fundamental frequency and its
harmonics; ie discrete frequencies, one per band; and was not regarded as an
antenna you could tune widely over a band.  That is because, once off center
fed, you violate any "balance" point you might have found, when you deviate
from the frequency the length of the antenna was naturally resonant at.
Indeed, they put up a wire, then tuned around to find the one frequency
where its single wire feeder did not have standing waves, allegedly.  That
became the frequency of use for that antnena, or on its harmonic bands.  No
scanning around the bands. The antenna and its feeder were one system.

It is a matter for debate if you can achieve no feedline radiation from an
OCF.  It is inherently unbalanced.  You would expect unequal currents to
flow in the two legs, one longer than the other and hence more impedance.
"perhaps" you could attain balance in a given installation using cable choke
beads on the feeder, and prevent feedline radiation of an objectionable
amount.  No balun is going to force equal currents into inherently unequal
arms of an antenna.  They are for the opposite case, going from a state of
balance, (equal current legs, and thus equal sized legs) to an unbalance
state as coax is.

Maybe avoid the OCF for multiband tuned antennas, or accept that the feeder
will be radiating.  In that case, abandon the balun at a feedpoint, and
simply add line length until you do not have a "hot" (RF) in the shack
syndrome.  On the other hand, Jack Belrose notes his simple L Network (2
components) tuner, handles the same range of matches as commercial Tee net
tuners.  Most ATUs use an L net, and then the issue becomes one of tuner
losses if a compact tuner with low Q components.
73
Stuart
K5KVH