Hi Art and group,
Taking the simplest example, a single wire Beverage fed with a
transformer and coax, the Beverage wire, the transformer primary, the
ground down lead wire and the ground are all in series. Currents induced
into the vertical wire flow through the transformer primary, just like
the currents in the Beverage wire do. As far as I can see it won't
matter whether the transformer is up at the level of the Beverage wire,
or down at ground level. It is still a series circuit, and the current
induced in that down lead flows through the transformer primary. How can
this be prevented?
Art said:
"Mine is a two-wire beverage Ken, with the rx connection taken at the
center tap of the matching transformer. A single wire as in your example
below would indeed act differently to vertical reception off the ground
wire."
I think that with a two wire Beverage the problem is the same. In
the "normal direction" the common mode currents pass through both halves
of the primary of the differential mode transformer (that is used for
the "reverse direction" feed) to the center tap, and then on to the
common mode transformer primary and then via the short vertical section
to the ground system. Just as in a single wire Beverage, the Beverage
antenna wire(s), the transformer primary, the vertical down lead and the
ground are all connected in series. Currents induced in the vertical
down lead will flow through the transformer primary, whether the
transformer is down at ground level or up at the Beverage antenna wire
level. How can the signal pick up on that short vertical wire not be
coupled through the transformer to the coax?
Misek says to slope the ends of the Beverage down to ground level
and Rauch says it wont help. I once had a bunch of Beverages over
terrain which sloped downward in a sort of concave fashion, such that I
could keep the Beverage wires straight along their whole length, while
having the feed end and far end at ground level, requiring no short
section of vertical wire for the ground connection. They worked great,
but that was a special situation that does not exist if you have only
flat land to work with.
Art, I am not disputing your results. If it works better for you
that way, then by all means keep doing it. I am just trying to
understand it.
Thanks,
Ken N6KB
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