To Topband....forewarded without comment
Carl KM1H
>Carl,
>
>In an earlier email, W8JI referred to the antenna system at AM station
>WVNJ, saying that they switched from elevated radials to a ground
>radial
>system and picked up several dB, and that this result brought into
>question the credibility of the engineer who did the Newburgh, New
>York
>elevated radial test and who installed the elevated radials at WVNJ.
>
>I have a copy in front of me of the Engineering Statement submitted to
>the
>FCC in regards antenna tests done at station WVNJ concerning elevated
>and ground mounted radial systems. Here are the pertinent quotes:
>
>"The objective of our limited field tests was to determine if a
>dramatic
>increase in field strength would result from using a conventional
>ground
>system in lieu of the elevated radial system. During the period of
>November 20 through November 23, 1993, 120 copper radials of size
>#10 and approximately 100 feet in length were equally spaced around
>the No. 3 tower of the WVNJ array. Since the No. 3 tower was used for
>the WVNJ non-directional antenna proof, it was selected for a
>comparison of the two antenna systems to determine if a meaningful
>change in the measured field strength could be achieved with an
>abbreviated conventional ground system. The results of the comparison
>of the elevated radial system versus the abbreviated 120 ground radial
>system are shown in Tables I and II. Comparison of the data in Tables
>I
>and II show that the tests as conducted did not achieve any
>substantial
>change in field strength over the measured field strength reported in
>the
>WVNJ antenna proof-of-performance conducted in October 1993.
>Based on the liimited number of 'before' and 'after' measurements, the
>abbreviated ground system performed nearly the same as the elevated
>radial system. "
>
>The Tables are too long to include in this message, but each Table
>includes a line entitled "Average Ratio Before/After" giving the
>averages
>of measured values for several radial/ground comparisons. The ratio
>is
>1.00 for comparing the elevated radial system alone to the elevated
>radial
>sysem PLUS 120 ground radials. The ratio is 0.97 for comparing the
>elevated radial system to only the ground radials. These results
>therefore show a 0 dB difference between a tower with elevated radials
>vs. a tower with elevated radials plus the grounded radials; and a
>difference of a tiny fraction of a dB between a tower with elevated
>radials vs. a tower with many gounded radials.
>
>If tests of additional ground systems at WVNJ were conducted after
>these tests, I do not have copies of them. They would, of course, be
>essential for verifying the assertion that several additional dB of
>signal
>were attained by the replacement of the elevated system with the
>grounded system, and for supporting the assertion that the original
>WVNJ engineer erred in his conclusions in re the efficiency of the
>antenna system and also erred in his work at Newburgh, NY.
>
>Again, Carl, the essential element of the elevated vs. ground mounted
>radial discussion is this: ALL of the theoretical and measurement
>data I
>have been able to examine has supported the thesis that a few elevated
>radials are fully equal in performance to a system of many buried
>radials.
> If ANYONE has any measurement data to the contrary compiled by a
>competent consulting engineer, that data should be provided
>IMMEDIATELY to you. Absent such data, I would consider the issue
>settled and the discussion closed.
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