----- Original Message -----
From: Tom Rauch<mailto:w8ji@contesting.com>
To: john battin<mailto:jbattin@msn.com> ; k1fz<mailto:K1FZ@prexar.com> ;
topband@contesting.com<mailto:topband@contesting.com>
Sent: Friday, November 19, 2004 7:24 AM
Subject: Re: Topband: Close to earth Beverage.
All this may be fine but with beverages 8 foot beverages,
on higher frequencies if I cut the beverage off and just
leave the feed, the signal stays the same. As the frequency
goes lower the effect diminishes but still is enough to
effect f/b and f/s. I have measured it.<<>>
I wasn't clear. I was talking about 160 John.
On ten meters it makes a big difference because radiation
resistance is a large part of the overall system impedance.
As I recall you measured end radiation using a "T" or
center-tapped 1/2 wl wire for termination.
When a 1/2 wl wire (with center used for ground) is placed
over lossy soil it actually receives quite well. If you look
at an eight foot high "T" antenna over lossy soil the
radiation of the horizontal wire dominates the pattern, even
in a model with perfectly homogeneous soil and perfect
balance!
The "non-radiating" termination "T" is anything but
non-radiating, and the field it radiates and responds to is
(no surprise) vertical. Short of installing 50 or 100
radials eight feet high, I can't think of any way to measure
vertical end-effect on 160.
I think some Beverage books and other sources have blown the
vertical end effect all out of proportion for bands where
the antenna is 1/50th to 1/100th of a wavelength above
ground. It started a few rumors or myths that just aren't
true.
73 Tom
This may all be true, but my measurements show that the signals off the back
and sides of my beverages are dominated by pick-up in the feed wire. If I am
listening to signal off the side, and cut the beverage off and just leave the
feed, the signal stays about the same. There is little that can be done about
it, except as was suggested at the start of this thread ,,,, lower the beverage
and trade off end effect for beverage performance.
John
K9DX
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