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[TowerTalk] Tower Height

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Subject: [TowerTalk] Tower Height
From: (Jim Rhodes KCOXU)
Date: Tue, 27 May 1997 23:15:07 -0500 (CDT)
>There has been a recent thread regards putting a ground screen at the
>base of the tower and extending (purportedly) for a modest distance
>from the tower throughout a housing lot.  There has been several statements
>regarding the effect on the take-off angle that the wire screen might or
>might not have.  I would only like to add my personal experience in this
>regard without comment on the effect of the below-the-antenna ground system
>vs. the effect of distant reflection ground some thousands of feet or miles
>While living in Tucson in 1966 and 1967, I constructed a 3 el 20, 4 el 15 &
>10 meter quad at 60 feet (Feb 1967 issue of QST).  The most pronounced
>propagation phenomena I encountered was that when the soil was dry, I was
>able to hear and to work Europeans with some success...... but when it rained,
>I couldn't hear jack squat for 2-3 days afterward on any long haul DX.  I
>attributed this (albeit it may be in error - if it is, please explain how)
>to the "virtual" rf ground being considerably below the literal ground when
>the soil was dry and therefore the take-off angle was considerably lower on
>transmit.  The received rf angle appeared to have tracked with that as well.
>When it rained, the conductive nature of the soil was enhanced and made the
>antenna considerably closer to the ground and hence the take-off angle was
>sufficiently higher enough to rule out long haul dx.
>Don't know if it was far field reflection or the field close at hand that
>might have caused that effect.  There can be no doubt, tho, as to whether
>it existed or not. I observed it many times.  Any comments?
>Rod,  W5HVV
>Remember!  Unconstructive flames give me gas!

You have to realize that the soil conductivity would change over a large
just under the tower. This would have the effect of raising ground level at the
fresnel(sp?) point.
Jim Rhodes KC0XU

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