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Re: ground problems
From: Phil Chalk[SMTP:philoc-at-ozemail-dot-com.au]
Sent: Wednesday, September 17, 1997 6:28 AM
To: Tesla List
Subject: Re: ground problems
Tesla List wrote:
> From: Bert Hickman[SMTP:bert.hickman-at-aquila-dot-com]
> Reply To: bert.hickman-at-aquila-dot-com
> Sent: Tuesday, September 16, 1997 11:44 PM
> To: Tesla List
> Subject: Re: ground problems
>
> Tesla List wrote:
> >
> > From: Geoff Schecht[SMTP:geoffs-at-onr-dot-com]
> > Sent: Tuesday, September 16, 1997 11:38 AM
> > To: Tesla List
> > Subject: Re: ground problems
> >
> > > From: Bert Hickman[SMTP:bert.hickman-at-aquila-dot-com]
> > > Reply To: bert.hickman-at-aquila-dot-com
> > > Sent: Tuesday, September 16, 1997 8:12 AM
> > > To: Tesla List
> > > Subject: Re: ground problems
> > >
> > > Tesla List wrote:
> > > >
> > > > From: Mad Coiler[SMTP:tesla_coiler-at-hotmail-dot-com]
> > > > Sent: Monday, September 15, 1997 6:55 PM
> > > > To: tesla-at-pupman-dot-com
> > > > Subject: ground problems
> > > >
> > > > I am back in Columbus for a while and have one problem. I am on
> the
> > > > second level in an apartment building. Does anyone have any
> suggestions
> > > > about how I can get a descent ground? I have been using the cold
> water
> > > > copper pipe to the sink but have been informed that it is a fire
> risk.
Probably less of a fire risk than a CMOS risk for everyone in the
building !I have a similar problem on 4th. Flr of 1961 brick building.
Been lucky so far, using building ground, but have good filtering both
sides of the NST, & very little run-time on a small coil.
> > I
> > > > suppose I might have to take it to a friends house if that is
> possible.
I'm fortunate to have a garage, that's my answer - guess you don't ??
> > > > So far I haven't had any noise complaints, but only because I
> havent
> > run
> > > > it past 8pm.
Neighbours keep thinking I'm welding in my flat - I say nothing.
> > > >
> > > > Mad Coiler
> > >
> > >
> > > Mad,
> > >
> > > Because of the use of plastic plumbing in many areas, your ground
> may
> > > not really be a ground. To determine if it is, take an ohmmeter
> and
> > > carefully measure the resistance between the ground connection
> (the
> > > third prong on a nearby AC outlet) and your cold water copper pipe
>
> > > ground. If you get good continuity (say 20 ohms or less), then you
>
> > > should be OK.
That proves it's some kind of ground at DC. 20R is a fair bit of
resistance too, with the reputed base currents in these things. The
resistance of course is just the start of the story. I figure the 20m
or so of 2.5mm^2 earth cable between my power outlet & Terra Firma
itself works fine at 50Hz. At a couple of hundred kHz it's likely to be
fairly reactive & not much of a 'ground' with the currents involved.
Running my baby (2 7/8" coil) in my lounge room, I can hold something
metal & draw ~1/16" sparks to the 'GROUNDED' case of the NST -
admittedly I'm in the field of the coil a bit, but at first it surprised
me.
> Another alternative ground is the ironwork of the building
> > > you're in if it happens to be an iron-concrete type structure, or
> as a
> > > last resort, the AC ground itself if you have a small coil.
> > >
> > > -- Bert --
> > >
> >
> > Hello All:
> >
> > I've used soldered-together sections of "chicken wire" as a form of
> radial
> > system (counterpoise) for my vertical ham antennas from time to
> time. It
> > works fairly well in that application and is quite cheap. Any
> > opinions/experience from other list members about how this might
> work with
> > a TC that needs a grounding system? It's an RF ground, though, not a
> safety
> > (green-wire, in the US) ground.
> >
> > Geoff (NQ7A)
This to me is one of those "better than nothing at all" situations, &
for that reason I'm all for it. Just curious about what frequencies
you're talking about ? - at 2m, or even 6, these things are practical on
your living room floor, as they become effective when the radials
approach or exceed 1/4 wavelength. Again I feel that at typical
"indoor" TC frequencies, this kind of ground would be of limited use.
However I stand by the 'better than nothing' line, & as an adjunct to
another earth it may assist. However, I'm talking out of my hat - the
real answer, as usual, is 'suck it & see'
>
>
> Geoff,
>
> Good point, Geoff. I considered suggesting a counterpoise, but it
> wasn't
> clear if Mad Coiler's apartment was wood/frame construction or steel
> beam/concrete. A counterpoise could work very well, especially if Mad
> Coiler lived on the first floor. Since Mad Coiler lives on the second
> floor, an elevated counterpoise would still work very well if he was
> in
> a steel/concrete building, and less so if he lived in a wood/frame
> environment.
>
> -- Bert --