----- 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 6:52 AM
Subject: Re: Topband: Close to earth Beverage.
I believe the advantage you are seeing with a low beverage
is the reduction of pick-up from the feeds. When you think
about it, the 8 foot vertical at each end of the higher
beverage is 1/4 wave on 10 meters and this signal dominates
the signal picked up by the beverage. At lower frequencies
the effect is lesser, but still effects f/b and f/s
signals.>>
I don't see how that could be. The radiation resistance of a
short vertical with uniform current can be closely
approximated by multiplying 1580 times height in fractions
of a wavelength squared.
A 1/100th wavelength tall vertical with uniform current has
a radiation resistance of .15 ohms.
.15 ohms radiation resistance is a tiny part of 400-600 ohms
antenna impedance.
The mechanism going on (I've never seen an improvement here
laying a Beverage on the ground) is probably the velocity
factor of the wire has decreased increasing effective
length, or he has managed to position a null on a dominant
local noise source.
What everyone seems to ignore is the entire Beverage from
end-to-end receives vertically polarized signals. It is very
unlikely that two mismatched 1/100th WL long verticals would
ever inject meaningful noise or unwanted signal to a wire 1
or 2 wl long that the 1-2 wl long wire wouldn't already be
receiving.
If the ends had enough sensitivity to change noise level,
the pattern would be terrible. It all comes back to antenna
pattern.
73 Tom
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.
John
John
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