Topband: [bevantennas] Ground screen under beverage....

[donovanf at erols.com]

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 at karlquist.com> 
To: donovanf at erols.com, topband at 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 at 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