Hi Rick,
I'm not aware that any details of this phased array Beverage design
were ever published. M ost likely it was documented only in internal
government engineering reports.
These very large phased Beverage arrays continue to operate with
excellent results up to 30 MHz, some of its unusual design details
may be significant only to their high performance at the upper
end of their frequency range.
Just how large are these phased arrays? Yes, there's more than one array...
They're only 300 feet long but 2500 feet wide (yes, 2500 feet) ! That
should give you a clue that they don't operate near any of our lower
frequency HF/MF ham bands.
An interesting aspect of its design is that each Beverage in the arra
uses three wires separated horizontally by about four feet, similar
to the the three wires used to broaden the VSWR bandwidth of military
and commercial rhombic antennas. The three wires join together at both
the feed point and at the termination.
Many decades ago these phased Beverage arrays replaced phased
rhombic receiving arrays, two high and two wide.
I'm sure some antenna modelling would provide some clarity to
your questions. I wasn't involved in aspect of the design activity.
73
Frank
W3LPL
----- Original Message -----
From: "Richard (Rick) Karlquist" <richard@karlquist.com>
To: donovanf@erols.com, topband@contesting.com
Sent: Friday, October 2, 2020 3:32:48 PM
Subject: Re: Topband: [bevantennas] Ground screen under beverage....
On 10/1/2020 10:53 PM, donovanf@erols.com wrote:
>
> The engineer who lead development, testing and evaluation of the array
> explained that the ground mats served two purposes:
>
> - 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.
> W3LPL
>
I don't buy the engineer's reasoning here. If we use superposition
into vertical and horizontal electric fields, it seems to be apparent
that the ground mat would do nothing to prevent the last 50 feet from
acting like a sloping vertical with respect to vertically polarized
waves. If anything, it would make the vertical work better, as
verticals always do when radials are added.
I could believe that the mat would prevent the last 50 feet from
acting like a Beverage, but that "solves" what is a non-problem.
I think everyone including the engineer agrees that 4 vertical
feet is 4 vertical feet no matter how many horizontal feet
are added. Because of superposition.
I am thinking that a very simple test of this would be to
do an A/B test of the pattern with only the last sloping 50 feet
connected, comparing with and without the mat. I'm surprised
that the engineer didn't do this as confirmation.
Is there any article that establishes that the 4 foot vertical
drop at the end of the Beverage is actually significant to
the overall performance of the Beverage? I've never seen such
an article myself. It is hard to imagine that only 4 feet of
conductor would pick up much signal.
Rick N6RK
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