Topband: Question abt gain in bi- vs uni-directional Beverage

[k6se@juno.com]

Fritz, K4OAQ wrote:

"Recently I was having a discussion with a friend abt adding switches at
the terminating resistor in order to switch from uni- to bi-directional. 
He asked why I just didn't make them bi-directional & forget abt having
to add a switch.  When I answered that the uni-directional had more gain
(e.g. in the NE direction) than when it was bi-directional, he said he
didn't think that was the case, or at least the additional gain was only
marginal.  My
> thot is that the gain is significant.  I've done some reading and can't
find anything at by level that suggests yes or no to whether there is
more gain."
----------
There is no differance in the gain of a Beverage with or without a
terminating resistor.  The resistor merely absorbs the energy coming from
the opposite direction, making the antenna unidirectional.
==========

"If the answer is that there is no appreciable additional gain with the
uni-directional Beverage, then why does it seem that everyone makes their
Beverage's uni-directional.  From my contesting viewpoint, the more I
hear (excluding noise!) the better."
----------
There's a good reason why you should make a Beverage unidirectional --
the signal-to-noise ratio of the antenna will be better.  In fact, that's
the primary reason for using a directional receive antenna on 160 -- to
have a better receive signal-to-noise ratio.  The gain of an antenna
hardly enters into the picture.  It's an antenna that doesn't receive
noise (either "sky" noise or man-made)  from all directions that matters.
 The more directional the antenna, the better its S/N ratio, regardless
of gain.
==========

"If I we were talking 1 or 2 wavelength Beverage's, would the answers be
any different?"
----------
No.  The same theory applies.  However, a 1- or 2-wavelength Beverage
would be a vast improvement over a terminated 1/4-wavelength wire.

If space limited, you're better off using a Pennant, Flag or Ewe etc.,
because they would have much better directivity (and therefore better
receive S/N) than a 1/4-wave terminated wire.

73, de Earl, K6SE

P.S.  Since Fritz's "Beverages" are only 1/4 wave long, they aren't 
acting like true Beverages.  I modeled one 1/4 wave long, 6' high and
terminated...it radiates straight up with no directivity...de W4ZV.




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