[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

Re: grounding question

Original poster: "Peter Terren" <pterren@xxxxxxxxxxxx>
I wire my cage to my HV ground and to mains ground. RF ground current with a good cage should be small . Using a RF choke completely disconnects the ground at TC frequencies and should never be used. Try it on a normal TC and see the sparks fly across it. Similarly a counterpoise is a partial cage only so still large currents to ground so shouldn't use a choke. An imperfect Faraday cage should have only small RF currents to ground but should still go somewhere otherwise there is a shock risk. The imperfect bit mainly arises from the way the HV is brought into the cage and filtering / voltage suppression at the point of entry. In summary, downunder opinion is that if using a cage then it should be grounded to HV ground and on to mains ground. Counterpoise and standard TC's need a good RF ground and should not be connected to mains unless tiny. 

Peter
http://tesladownunder.com


Original poster: "Lau, Gary" <Gary.Lau@xxxxxx>

I agree that a counterpoise would benefit by a connection through an RF
choke to safety ground, to establish a path for fault currents.

..... How to construct an RF choke between the RF and green-wire
grounds that can support a fault current and still isolate RF from the
mains ground?  Trouble is, I'm unaware of any actual measurements of the
magnitude of the RF transients that appear on our RF grounds.

Regards, Gary Lau
MA, USA



> Original poster: Jim Lux <jimlux@xxxxxxxxxxxxx>
>
> At 12:49 PM 10/9/2006, you wrote:
> >Original poster: Mddeming@xxxxxxx
> >In a message dated 10/9/06 1:27:38 P.M. Eastern Daylight Time,
> >tesla@xxxxxxxxxx writes:
> >Original poster: John <guipenguin@xxxxxxxxx>
> >
> >If I cant drive a grounding rod for RF ground, what is this counter
> >pose under the coil I hear people mention?
> >
> >Thanks,
> >
> >      John.
> >
> >Hi John,
> >
> >     A counterpoise is a type of "virtual ground". consisting of
> > foil, wire mesh (chicken wire etc.) or radial wires arranged in a
> > daisy wheel at least as long and broad as the coil is high or the
> > topload diameter, whichever is greater. This is placed underneath
> > the unit with RF ground end of secondary attached to it. The
> > topload "sees this as ground and all works. A foil one is cheapest
> > and easiest, but wastes somewhat more power in eddy currents.
> > Radial wires are the most efficient, but hardest to do and keep
> > straight. a large square or circle of wire mesh is a good
> > compromise. NOTE: During operation, the counterpoise is floating at
> > unknown high potential with respect to earth ground. DO NOT
TOUCH!!!!!
>
>
> For the latter reason, the counterpoise SHOULD be connected to the
> "green wire" safety ground.  I'd use a RF Choke of some sort, just to
> keep RF off the building safety ground.