Bill, I agree with your analysis and like you I wish there was a program like
HFTA out there that could handle a vertical radiator.
My remote QTH is on a gently sloping hill in all direction and is about 100m
above the surrounding farmland.
Here is a very rudimentary and non-scientific powerpoint which includes a copy
of the “vertical over sloping terrain analysis” from ON4UN’s book. I don't
know where he got this analysis or who did it. Does anyone know??
https://drive.google.com/file/d/1UP45c5MWaWvA0T9no4DHW060FSgC-3Pk/view?usp=sharing
<https://drive.google.com/file/d/1UP45c5MWaWvA0T9no4DHW060FSgC-3Pk/view?usp=sharing>
This analysis of an 80m vertical over sloping ground certainly shows that a
significant low-angle gain benefit of up to 11dB over a flat terrain vertical.
I include a comparison to other plots from Johns book showing how a vertical
over saltwater shows a similar outstanding low-angle response, which we have
all heard in action from various well place DX-peds on the saltwater. I
extrapolate this to 160m.
I can only assume that building a HFTA like program for a vertical is a bit
more complex than a horizontal radiator.
73, de steve ve6wz.
> On Jan 20, 2019, at 6:06 AM, Bill via TowerTalk <towertalk@contesting.com>
> 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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