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

[Richard (Rick) Karlquist]

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