Many years ago I was involved -- peripherally -- with very large phased arrays
of Beverage antennas installed over very poorly conducting soil (almost
solid rock) in which ground rods were completely impractical and
ineffective. The design of these arrays predated the availability of
general purpose computer-based antenna modelling; however, the designers
did develop custom method-of-moments software models of the array.
Importantly their design also involved extensive measurements of
individual Beverage antenna patterns and Beverage array patterns
by use of sophisticated airborne sensors.
Both ends of every Beverage in the array used fifty foot sloping wires over
conductive ground mats. Each mat consisted of chicken wire fencing
material about sixty feet long and ten feet wide. The mats extended about
ten feet beyond the feed point and termination connections to the mats.
The mats did NOT extend under the horizontal portion (the antenna portion)
of each Beverage antenna.
The entire array was installed in a secure fenced area with no possibility of
human or wildlife intrusion. Among other things that allowed antenna
height of only four feet which resulted in improved front to back ratio and
reduced sidelobes especially at higher frequencies.
The engineer who lead development, testing and evaluation of the array
explained that the ground mats served two purposes:
- substituted for ground rods that couldn't be used in mostly solid rock
- almost completely suppressed signals received by the sloping ends of the
Beverages by making them into efficient transmission lines with very low
spurious signal leakage compared to a sloping wires over poorly conducting
soil or vertical wires at each end of a Beverage.
73
Frank
W3LPL
----- Original Message -----
From: "Jim Brown" <jim@audiosystemsgroup.com>
To: topband@contesting.com
Sent: Friday, October 2, 2020 3:46:56 AM
Subject: Re: Topband: [bevantennas] Ground screen under beverage....
On 10/1/2020 5:03 PM, Grant Saviers wrote:
Worse than "not the best" or "not a good idea" from prior experimentation.
And a clear indicator that whoever proposed it failed to learn how
Beverages work! It all goes back to Mr. Beverage's original patent more
than a century ago.
Beverages DEPEND on lossy earth beneath them, and DXpeditioners who have
tried them over high conductivity ground near the sea quickly learned
that they don't work.
73, Jim K9YC
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