On Sat, 24 Oct 2009 19:56:58 -0400, Steve wrote:
>Anyone recall discussions or references to the operation of verticals
>over sloping ground?
>My back yard slopes at perhaps 10 or 15 degrees, just exploring the
>possibility of a low band (160 or 80 or 40 meter) vertical. Elevated
>radials seem impractical, so I'm wondering what would be the effects on
>the vertical radiator if the ground radials are not 90 degrees?
Don't worry about it. The terrain that matters is not the near field,
but in the first 5 miles or so running radially from your QTH. My 160M
vertical is ground mounted with about 70 radials that vary in length
between 30 ft and 140 ft (the short ones are close to the building that
houses the shack). The ground where the radials are slopes down about 30
degrees from Az 90 degrees to about 180 degrees, but is fairly flat
elsewhere. To the north and east, the ground is flat for about 100-150
ft, then dives into a deep ravine. None of this seems to affect field
strength. I think you've heard my signal on 160 -- I'm not the loudest
signal on the band, but the vertical works fine in all directions. (On
80 and 40, I'm using high dipoles).
Rudy Severns, N6LF, recently did some research to show that having no
radials in one direction (like if your vertical is up against a house)
reduces radiation in that direction by a few dB. His work was extreme --
no radials at all for half of the full circle. This is due for
publication in one of the ARRL publications (Contester?) in the next
month or two. In his extreme case, it was 3dB down in the 90 degree
direction, but less than one dB in the opposite direction.
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