Brian Kelly wrote:

Mark Keith wrote in message ...
Brian Kelly wrote:


Center-fed dipole-based antennas don't need station or installation
site RF grounds. Horizontally or vertically oriented. All end (base)
fed verticals need RF gounds so don't use 'em in your situation.

I've never needed an rf ground for a base fed half wave. A decoupling
section with radials is an option to reduce feedline radiation..Not
required to work though. MK

You lost me Mark. You have a vertical half-wave wire fed at it's base.
You have an unbalanced L/C network which matches the very high
feedpoint impedance to, say, a random length of 50 ohm coax. What do
you do with the coax braid and the ground side of the tuner?

Brian w3rv

Using the usual "gamma loop" feed I generally prefer for those, the coax
shield is connected to the "ground" side of the single turn coil. "appx
9-11 inches dia. for a 10m version" I usually make these from 3/8
tubing... That point is at ground potential as far as the mast, base
support, etc..The other side of that coil is connected to the base of
the radiator. The center conductor taps the single turn coil at the
point for best match. A capacitor from ground to coil "hot" side is
optional. In general you use about 50 pf for a 10m version. Double for
20m, double again for 40m, etc... I use a piece of coax for those. "open
end, don't short" For 10m, it's only about a foot or so long...Look at a
cushcraft 10m ringo. "model AR-10". They have PDF manuals on the web
with pix..That is the same basic design I use. They also make 2m
versions...BTW, I make these from tubing, and are self supporting.
Rarely use wire...These antennas work quite well. Good 10m antenna...The
higher, the better..Add decoupling, even better, but not required to
work..MK
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