The R7000 is electrically 3/8 wavelength, with feedline decoupled by
a choke/capacitor
system. The 'radial' whips are there for capacitance.
I had one up in Vermont, as a utility antenna, and had an opportunity
to compare it against
an elevated ground plane with 4 radials, on 40m. The antennas were
300' apart, and at approximately
the same elevation. The r7000 was fed through 300' of 9913, and
was mounted 10' above grade,
which was 100' above my house, on the back hill.
The ground plane was fed through 150' of rg213, and was hoisted up by
haliard from a 140' pine.
The differences between the two antennas, on 40, were so small that
qsb more than swamped them out,
as I did the a/b switching.
The same r7000, down here in suburbia, is virtually useless, due to
power line noise pickup.
I would suspect that a buried ground plane beneath such an antenna
would have no impact, unless
the radial system extended out to the point of first-reflection, and
improved ground conductivity.
N2EA
-----Original Message-----
> From: Rudy Severns <n6lf@arrl.net>
> Sent: Sep 15, 2008 9:16 AM
> To: towertalk <towertalk@contesting.com>
> Subject: [TowerTalk] R7000
>
> Some multiband commercial verticals will work without a ground system.
> During my experiments earlier this year I tried an R7000 first with
> a large
> ground system and then removed the ground system. I could barely
> tell the
> difference. This check was done on 40m. Didn't see if this held
> for the
> higher bands but I suspect it would.
>
> The signal from the R7000 was a couple of dB lower than a full 1/4-
> wave with
> the same ground system. I suspect that was mostly due to loading
> inefficiency which is to be expected in short loaded antennas.
>
>
What was the height of the base of the R7000 above ground?
i.e. was it basically acting as an elevated (shortened) vertical dipole?
(with the feedline and/or radials at the bottom acting as the "other
half" of the dipole)
-0-
Jim Jarvis, MBA
President - Executive Coach
The Morse Group, LLC
732 548 5573 office 908 410 9130 cell
People-Process-Strategy: Achieving Results in a Changing World
www.themorsegroup.biz
coach@themorsegroup.biz
Read our latest newsletter. Go to: http://www.themorsegroup.net/
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