It doesn't work that way. You need two feed lines, each going to
opposite ends, each end having both a transformer and resistor, and
relays that switch them in or out to flip the direction.
Not necessarily. I have several bidirectional Beverages made from WD1A
field phone wire. That stuff is like zip cord with a light twist. I have
just one feedline running to one end of each Beverage. At the far end is
a reflection transformer rather than resistor tor termination. At the
feed end, a DPDT relay is used to select direction. In the "reverse"
direction, the incoming signal is fed into the far end of the twisted
pair in differential mode by means of the reflection transformer, where
it travels back to the feed end using the Beverage as twisted pair
transmission line. Voltage to power the direction switching relay is fed
over the coax. By the way, these work equally well if not better fed
somewhere along the length of the Beverage. The entire length is still
used in both directions, so there is no performance loss. However this
requires a different circuit at the feed point and two reflection
transformers.
I got the basic idea from here:
<http://win.i1wqrlinkradio.com/archive/OH2BEN_Reversible_Beverage_Array-20-10-2007_04d.pdf>
I made some changes including feeding relay power over the coax and the
center feed, but I have never found time time to properly document my
variation.
73,
Paul N1BUG
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