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RE: Capacitor Help



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

Hi Gerry:

I think the point of the choke is to prevent the stuff tied to RF ground
from being elevated to a hazardous voltage should any number of fault
conditions occur.  I know that I have a very substantial RF ground - two
very long buried copper pipes and a copper sheet, but the DC (or 60 Hz)
impedance to my green-wire ground doesn't even register on my DMM's high
resistance range!  I've thought about such a safety choke, but it's on
my to-do list...

I agree that parasitics in most any choke will provide some capacitive
path back to the mains ground.  Unresolved is how to minimize that, and
just how much inductance is needed.  But one must also bear in mind that
there are comparable paths through the NST to hot & neutral.  I
dutifully use a commercial EMI filter to minimize that, but have no idea
just how effective that is - probably not very at my 82KHz resonant
frequency!

Regards, Gary Lau
MA, USA

> Original poster: "Gerry  Reynolds" <gerryreynolds@xxxxxxxxxxxxx>
>
> Hi Terry,
>
> This has been mentioned before as a solution to indoor operation.  I
> really dont think the choke would help if there was an impulse on the
> RF grouind. Like you say, an arc could go around the choke.  Chokes
> of any design have their resonances and become capacitive above
> certain frequencies.  I think an impulse would go thru the parasitics
> of the choke even if it didn't arc over..
>
> Gerry R
>
>
> >Original poster: Terry Fritz <vardin@xxxxxxxxxxxxxxxxxxxxxxx>
> >
> >I have never mentioned this before, but I have often contemplated
> >using a choke between the RF ground and the AC line ground.  The AC
> >line ground could then still provide 60Hz safety but the choke would
> >block the RF from the AC ground.  My DRSSTC has this but I have
> >always used an RF ground too...  One problem with running only the
> >AC ground is that if the RF really wanted to arc across the choke,
> >it easily could...
>
>
>