Topband: Close to earth Beverage.

[Chuck Hutton]

Professor Beverage saw it John's way. His original Beverage antenna article
in 1922 (November QST, pages 12 and 13) and a 1983 article (January QST,
p.14) both mention the problem of pickup from the downleads and how serious
the problem is at 160 and 200 meters.

It will be awhile before I have the automated Beverage raising & lowering
equipment ready to test this myself.... 


Chuck

-----Original Message-----
From: topband-bounces at contesting.com [mailto:topband-bounces at contesting.com]
On Behalf Of Tom Rauch
Sent: Friday, November 19, 2004 4:52 AM
To: john battin; k1fz; topband at contesting.com
Subject: Re: Topband: Close to earth Beverage.

John said:
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.>>

Tom said:
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


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