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."
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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.
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"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."
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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?"
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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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