wrote:
>My shack is on the second floor of my house. No other options. I had
>the same situation years ago in another house, another city. I was
>just getting started in the hobby and several "old timers" told me
>about a method of getting a good RF ground on the second floor. It
>involved using capacitors on a piece of RG-8U. You installed one at
>the shack and at the ground across the shield and center conductor.
It doesn't work any better than a single fat wire (and possibly less
well), for the reasons Cortland and Ken have already given.
Depending on the configuration of your antennas and feedlines,
attempting to provide an "RF ground" in an upstairs shack may do more
harm than good, because in some situations it may create a path for RF
currents to flow through the shack.
A friend using a quad above his house found all kinds of RFI problems in
his own house and the neighbor's house close by, but these almost
disappeared when he disconnected the "RF ground" wire running down from
the shack. He then realised that since the quad doesn't actually need an
RF ground, the problems were due to his having invited ground currents
to flow by providing a path for them. He reasoned further that some
currents would still be flowing through the mains ground conductors, so
he RF-isolated the mains to the entire shack by winding *all* the
conductors through a stack of ferrite rings. The remaining RFI
disappeared completely - so this was a case where the cure was not to
ground the whole shack to RF, but to "float" it!
I hate to keep banging this drum, but an RF current probe will tell you
what's really happening.
--
73 from Ian G3SEK 'In Practice' columnist for RadCom (RSGB)
Editor, 'The VHF/UHF DX Book'
http://www.ifwtech.co.uk/g3sek
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