On Wed,3/9/2016 5:56 AM, john@kk9a.com wrote:
> First, any thoughts as how the terrain where the antennas are located
> will affect operation? Also, any thoughts on how the big slope from
> the antenna location to the ocean will affect the signal. On HFTA it
> is a big help on 80 with dipoles etc. but I'm not sure how it will affect
a vertical system.
"N6BT gave a very interesting talk at Pacificon last fall (2015)) that
addressed something like this. He set up verticals (memory fails, I think it
was 20M) at three locations on a plateau with drop-offs on all sides. At the
edge of the plateau facing SA, he worked SA and no JA. At the edge facing
JA, he worked JA and no SA. In the center of the plateau, he worked neither.
He used a drone to measure the vertical pattern and found the field strength
increasing a bit below zero degrees elevation.
It's worth looking for his slides or having a chat at Visalia. He's usually
there. I just tried to find slides on the internet without success.
73, Jim K9YC"
My HF mobile mountaintopping experience (using a vertical) supports exactly
what Jim K9YC related.
As the mobile moves toward the slope that faces downhill in the direction of
the DX there is a huge positive gain in signal strength. Interestingly the
very edge of the hill is seldom the best location for the best signal but
usually it is found farther back and away from the edge. On some flattop
mountains or hills I would drive the vehicle toward the desired edge facing
the DX (say NE for EU) and found that I may have not heard anything in the
center of the flattop but as I headed toward the NE edge the signal started
getting stronger. Once I got toward the edge and the signals weakened I
would back up until they got loud again and work to the NE from there.
Driving toward and back away from the edge of the hill side was almost like
rotating a beam for the best signal -- the difference in signal strength was
night and day.
Prior to hilltopping I always thought that the best signal would be at the
very edge of the slope but it seems like it is 20' to 50' back from the edge
-- at least with the mobile.
Best, John NA6L
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