The fact that antennas are not guaranteed to be balanced means that a
tuner that tries to force balance by grounding the center of the output
coil or capacitor or the (GASP!) balun often leads to unbalanced line
currents. The Z match likely tries to force balance that way. The
Johnson matchbox tries to force balance. My tuner doesn't. because I
don't ground the center of the coil or capacitor on the secondary. I let
the antenna set the feed line balance and that will make the feed line
more balanced.
Another factor besides unequal environs for each half of the antenna,
the feed line not being at exactly right angles to the antenna will also
cause some unbalance, even when the tuner doesn't try to force balance.
Because earth is so abundant, achieving true balance in a tuner is at
least as difficult as measuring it without destroying the balance.
73, Jerry, K0CQ
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