[CQ-Contest] Two wire Beverage

[Garry & Yelena]

On a two-wire Beverage, the termination is the other terminated
port--the one not fed. Also, any reflection due to mismatch will cause
the reflected energy to end up in the other port, effectively reducing
front-to-back ratio for that port.

The simple far-end termination--one wire open and one grounded, will
work well, and I have used this for about seven years. However, this is
not a matched condition, and a transformer at the end, to provide the
common-mode to differential transformation, is better. See Misek's
Beverage Antenna Handbook, published by the ARRL.

As for the impedance of the transformers at the feed end, the balanced
transformer should match the parallel impedance of the two-wire
transmisison line, while the single-ended transformer should match the
common-mode impedance to ground.

Misek also shows how to feed the two-wire Beverage at the center---or
off-center, for that matter. This may be the ideal method for some
locations.

I am planning to rebuild my two short two-wire Beverages, which are made
of hookup wire and which have broken countless times here in the forest.
I am going to spend some money and use window line--it's strong, almost
invisible, and its velocity factor will electrically lengthen the
antennas by about 10%, not to mention that the impedance will be known,
and not guessed at.

-- 
Garry Shapiro, NI6T
Visit the Northern California DX Club home page:
http://www.ncdxc.org


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