A good way to think about this kind of "antenna on the side of a hill" is to
rotate the pattern for flat ground to the angle of the hill.
So, if your main lobe were at say, 10 degrees above the horizon, and you're on
a 10 degree slope, your new main lobe is at the horizon in the downhill
direction, and 20 degrees above the horizon in the uphill direction.
The actual angle of the vertical radiator doesn't make a huge difference
(especially if it's "short" compared to a wavelength).
For what it's worth, 10 degrees is about 17% grade, so pretty steep. Most
roads/streets are max around 6% (4 degrees)
On Mon, 13 Jan 2025 18:57:53 -0800, Jim Brown <jim@audiosystemsgroup.com> wrote:
On 1/13/2025 6:05 PM, RONDALL SPENCER wrote:
> Im building a 160 meter vertical out of rohn 45. The tower will be sitting on
> a hill side vertical with the ground sloping about 15 deg going down towards
> the west. Burried radials. How will this effect the transmit angle pattern
Several years ago, the fine antenna design engineer Tom Schiller, N6BT,
has done extensive research on verticals, including the effect of
sloping terrain. He has presented results of disciplined measurement of
a vertical near a a drop-off, showing that it strongly improves low
angle radiation in the direction of the rolloff. In general, the closer
to the drop-off, the better. I think he did this work at frequencies
well above topband, but it's likely to carry extend down there.
73, Jim K9YC
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