When I lived in an apartment in Farmingville, NY (Eastern Long Island), I
placed my Butternut HF6V vertical near the top of a hill ~400’ away and fed
with 600’ of RG8X. The slope was about 10 degrees downhill from Northeast to
Northwest from an elevation of ~290’ ASL and ~ 6 degrees uphill to the South –
the hilltop was about 400’ behind me up another 30’ in elevation. I used about
60 1/4 wavelength radials – 40 of which I had pointing downhill. It was at
the bottom of the sunspot cycle (1987) and I was able to hear and work almost
anything in Asia over the pole on 40 and 80 that stations with yagis and
4-squares had trouble hearing. There is no doubt that the negative horizon
significantly lowered the angle of radiation of the vertical in the direction
of the steep slope and the hill behind the vertical effectively cut off the
lowest angles of radiation behind it. I also experienced this phenomenon to a
smaller extent on a lower ~8 degree sloping hill in a different direction
(slope downhill to the West) where signals to the East were reduced.
Dave, NN1N, with his 4-square on his dramatically downsloping hill about 50
miles NE of me, used to consistently hear and receive reports of 1 – 2 s-units
better than me on 80 with my 4-square. This was especially noticeable on long
haul 80 M DX paths to HS0/BY/9M2 longpath (the direction of his downslope). We
noticed a similar phenomenon on 40 LP to HS0/9V/9M6 but he had a yagi at ~ 100’
on 40 to my 4-square so it was not an especially useful comparison.
He attributed the difference in performance on 80 to the sharply downsloping
radials from his hilltop qth. We were fairly even in receive and transmit
signal strength in the other directions.
Although these are anecdotal and not scientifically tested observations, they
were consistent and stable over a period of years. There is no question that a
vertical or vertically polarized antenna will experience an enhancement on low
angle paths in the direction of the downward slope with an equally likely
reduction in low angle signal paths in the direction of the upward slope. I
don’t know however whether there is an enhancement in high angle lobes with a
vertical in the direction of the upwards slope.
73
Bob KQ2M
From: n0tt1@juno.com
Sent: Sunday, January 20, 2019 11:05 AM
To: john@kk9a.com ; Towertalk@contesting.com
Subject: Re: [TowerTalk] 80 meter vertical
I've wondered about that myself RE the vertical on a slope. I did
a quick model of a 40m vertical that is leaning 45 deg over flat ground.
If the vertical is say, leaning toward North, the elevation plot shows a
little
more than 3db "loss" in the vertical direction (cloud warmer). The
azimuth plot shows ~4db F/B ratio that favors the "South" direction.
Charlie, N0TT
On Sat, 19 Jan 2019 21:58:31 -0500 <john@kk9a.com> writes:
> That is a great question, I have wondered this many times when
> operating on
> the sloping terrain in VP2V and KP2. To my knowledge there is no
> modeling
> software that will show a vertical's pattern on a hill.
>
> John KK9A
>
> Tom Osborne w7why wrote:
> Hi All
>
> I have tried putting up an 80 meter vertical 3 or 4 times. No
> matter what
> I do, it is never better than my twinlead fed 80 meter dipole up
> about 65
> feet.. This is both on close in stuff and longer range propagation.
>
> I tried it with the radials on the ground, with the feed point
> elevated
> about 6 - 8 feet with 4 raised radials, and about every combination
> I can
> think of.
>
> I was wondering if living on the side of a 450 foot hill makes a
> difference? The hill slopes down to the bay below my house.
>
> I have a 20 meter HB beam up about 25 feet. f I walk to the east
> about 25
> feet, and look back, the 20 meter antenna looks like it is about 60
> feet
> up. Goes higher as I walk farther east down the hill.
>
> Do verticals work poorly on the side of a hill, or does it make any
> difference at all?? Thanks and 73
>
> *Tom W7WHY*
>
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