At 10:30 AM 12/29/2006, Phil Clements wrote:
> > Subject: Floating Elevated Radials
> > >In transmitting systems elevated radials should never have a ground path.
> > >Grounding elevated radials reduces efficiency.
> > >If the house has a lot of noise and you receive on the transmitting
> > antenna >you might not want to directly ground the antenna ground system
> > to the >house. This is especially true with a small radial system.
> > >73 Tom
> My elevated radials float, and are connected directly to the shield of the
> feed line. (7/8 inch Heliax.)
> When the other end of the Heliax is connected to the output of my amp, it
> is "grounded" to the "house" central grounding point because the chassis
> of the amp is strapped to it. Are you saying that the amp and transceiver
> should be isolated from "house" ground also? If so, just how much
> efficiency is gained?
I would imagine that the amp's case has a connection to "green wire"
ground through the power cord, for safety reasons. One could use an
alternate grounding scheme (e.g. from a grounding lug on the amp to
your grounding system) as long is it's a permanent connection (i.e.
there's no way the amp gets power applied with the ground disconnected).
Unfortunately, with most amplifiers, the case ground is the same as
the RF ground, which makes it a bit of a challenge to come up with a
"good" grounding system without loops, etc. So, you hope for the
best by short runs all to a common point, etc.
> It has always been common practice to DC ground the radials of a ground
> plane antenna via the tower and its ground rod system, and by strapping
> the shield of the coax to the tower ground system at the base of the
> tower. Are you saying this method has less efficiency? If so how much
Besides, the antenna system MUST be connected to the earth ground to
meet code. Typically, connecting the shield of the coax to the
building electrical safety ground at the point where the coax enters
the house would be the way to do it. In the Cable TV world, they have
inexpensive grounding blocks designed just for this..
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