Re: An Electrolytic ground plane

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: "Jim Lux" <jimlux-at-earthlink-dot-net> 

What you describe makes a fine DC ground, and might provide a suitable
connection for grounding lightning impulses, but doesn't do much for RF.
The RF ground properties are going to be more determined by the type of soil
you have, and most particularly, the water content.

All an electrolytic ground will do is dissolve your ground rod more quickly.

For RF grounding, what you want is a GOOD conductor that is CLOSE to the
coil (i.e. a short wire from bottom of secondary to ground), as in directly
underneath it.  Sheets of aluminum or copper would work quite nicely.
Chicken wire/aviary netting would be a close second.

Unless you are making sparks 50 feet long, the earth properties aren't going
to be all that important.

Of course, if you dispense with the ground plane, and run a wire to a ground
stake, then what you are really depending on is the RF conductivity from
that rod to the floor under your coil.  If you run your coil over a concrete
floor, then you're actually in pretty good shape, because concrete is a
fairly good conductor.

It's important to remember that Tesla Coils are neither electric power grids
nor HF antennas, and most of the literature you will see on grounding
pertains to those two applications.  Even if you look at MF and LF antenna
grounding systems, they're not really relevant, since in the antenna case,
what you're interested in doing is propagating a wave away from the antenna.
However, in the sense that the typical broadcast worker wants to minimize IR
losses in the antenna system, as you do with a Tesla Coil, then the advice
is sound.  The classic George Brown 120 radials scheme would work fine.
Note that in his work, and in much subsequent analysis (Rudy Severns did
some nice work in connection with vertical antennae for hams) some general
expressions for the current density induced in the earth are derived,
allowing you to optimize the length and number of the radials.  In general,
extending the radials a bit more than the height of the antenna is
warranted.

Taking this for the TC world, it would turn into the usual recommendation
that the conductive counterpoise/ground plane should extend out as far from
the TC as the top of the TC is above the counterpoise.  If you have a 4 foot
high TC sitting on a 2 foot high table, your counterpoise should be on the
order of 12 feet in diameter.

For safety, you should connect your RF ground to the "greenwire" ground, but
that can be a high RF impedance.  It's to keep you from getting zapped by
50/60 Hz line current.  In fact, a choke might not be a bad idea, to keep RF
out of the greenwire ground.

----- Original Message -----
From: "Tesla list" <tesla-at-pupman-dot-com>
To: <tesla-at-pupman-dot-com>
Sent: Saturday, July 10, 2004 8:51 PM
Subject: Re: An Electrolytic ground plane


 > Original poster: "john cooper" <tesla-at-tesla-coil-dot-com>
 >
 > All:
 >
 > After some thought regarding this DeoxIt and conversations with some
 > advanced coilers, I've been forced to start from scratch and need some
 > advise on constructing the best possible electrolytic rf ground
 > plane.  I've got an 8 foot copper clad rod driven into the ground about 4
 > feet from the coil in question.  I do soak the area with water and Bob
 > Svangren suggested digging around the rod and burying rock salt which will
 > leach further down into the soil.  Are there any metallic salts or ???
that
 > will be more effective than rock salt?  If I can figure out how to
 > transport a few 8 foot ground rods in my Jag I'm going to add two more
this
 > weekend and will solder them together with wide strips of cu or 1/2" cu
pipe.
 >
 > Here's another real basic question that I'm remiss in not knowing but what
 > is the best test to determine the 'quality' of said ground plane?  Only
 > after this tested 'upgrade' can I then feel comfortable in testing the
DeoxIt.
 > John
 >
 >
 >
 >