> You may have seen one of those dual square boom logs
> where the coax runs into back-end of one of the square
> tubes and then all the way up the inside where it attaches
> to the feed point at the front-end.
The boom acts like a sleeve balun, since the rear area of
the log has the lowest voltage. Some Jerold commercial VHF
logs were built that way, although they still had some coax
common mode currents. Someone looking from the ground and
not examining the antenna would see the feedline exiting the
antenna rear, although it went through the boom to feed the
front!
Having the coax exit at a low-voltage point improves the
isolation of the shield.
It's important to remember cross-fed arrays of end-fire
dipoles with close spacing always fire towards the
feedpoint. Non-crossed elements fire in the direction of the
traveling wave on the transmission line, but have very poor
gain for a given length. Your example of the K9AY, which is
really two cross-fed verticals, is a good one.
73 Tom
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