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" <[email protected]> To: [email protected], [email protected] Sent: Friday, October 2, 2020 3:32:48 PM Subject: Re: Topband: [bevantennas] Ground screen under beverage.... On 10/1/2020 10:53 PM, [email protected] 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 _________________ Searchable Archives: http://www.contesting.com/_topband - Topband Reflector
