[Elecraft] K2 Tuner?

[Don Wilhelm]

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 ...