There are also anecdotal (& super station proven) and literature
examples of yagi gain enhancement when "back to" an upslope. Again not
something NEC can handle. Probably more complex with vertically
polarized antennas but the reflection gain might be meaningful.
Grant KZ1W
On 1/20/2019 5:06 AM, Bill via TowerTalk wrote:
Several people have mentioned the effects of a hill on a vertical or vertical
system.
I also know of no program that allows terrain to be considered for a vertical. Several
people who I consider informed came to the same conclusion I did, it enhances the signal if it
is a downhill slope and is detrimental if is an uphill slope. For example, if one looks
at a Yagi at one wavelength over flat ground and then at one over sloped terrain, you can see
how the angle has dropped. Likewise, if you look at the flat results and then the print
out of the uphill slope, it is easy to see the low angle has been attenuated.
It's my belief and some antenna gurus, that the steeper the slope, the lower the angle if down slope, and the more attenuated if up
slope.. At my QTH I have a huge downward slope to EU and NA and a huge up slope to the top of Mauna Kea (14000 feet) which is LP
for EU and SP for VK/ZL. On 80 I have a 4 sq and on 160 a bent vertical and a very good symmetrical ground system. For the
same conditions and distances I can tell you the signal is much better in the direction of the down slope than the up
slope. Is it a scientific test? No. However, it does indicate that if one has a big slope (in my case a 1:6 slope
uphill and downhill.) it does affect how a vertical performs. Mine and several others educated guess? Going downhill at my
place probably lowers the angel at least several degrees. No, I'm not sure if the angle is elevated in the up hill
direction. No doubt though it is attenuated.
Those who have heard me on 80 and 160 in EU and NA will agree that the down
slope helps the signal.
Bill KH7XS/K4XS
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