Ron and all,
Thanks for 'singing my song'. I have long advocated that the
antenna/feedline system is influenced by the electrical position of the
(electrical) ends of the antenna than any other factor. No matter how
you analyze an antenna, the current at the end of an antenna wire must
be zero. Think about it and you perhaps come to the realization that it
is a fact and is more of an influence in determining antenna balance
that any balun or other choking device.
Where a choke balun is important is in decoupling the *outside* of the
coax braid from the current on the inside of the braid. Even in coax,
the current is balanced if you consider the current on the center
conductor and the inside of the shield. However, when the current on
the inside of the shield reaches the end of the coax, it finds 2
conductors - one is the antenna wire or one side of a parallel feedline,
and the other is the outside of the coax shield. The RF current will
dutifully split onto both conductors if there is no means to prevent it.
So the result can be that RF is coupled back to the operating position
on the outside of the coax shield. That can unbalance the currents on
the antenna or parallel feedline since the 'end' of that side of the
antenna has changed into a complex form rather than a simple length of wire.
Think about it a while and you may come to the same conclusions.
73,
Don W3FPR
Ron D'Eau Claire wrote:
snip...
I have measured the current in each leg of the feed line with an unbalanced
tuner and no balun and found it very well balanced. The balance in the
currents seems to have a lot more to do with the load (antenna) than the
source.
snip ...
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