Re: Portable coils

Problem is, the coil would need to be portable. This precludes the use of an
RF ground. I was thinking that if I made a bipolar, centre driven coil, and
caused the sparks to pass between the ends of the isolated secondary, then
there should be no need for an RF ground. Hopefully if the coil was sparking
in this configuration there would be no RF interference with lab kit etc.,
provided of course that I put sufficient RF protection round the transformer.
You could also use a counterpoise.  If you mount the coil on a cart of some
sort, the counterpoise can be fixed to the bottom of the cart above the 
ground surface.  A counterpoise is a conductive plate that is placed above
the ground a short distance and makes the coil "think" there is a ground there.
Here is an old description from Richard Quick about a cart he made with a 
counter poise.
 Below the table top there is a heavy brass plate.
The brass plate has a short length of one inch ground strap
soldered to it. This ground strap may be passed through a slot in
the table top to make a direct connection with the base of the
Tesla resonator. The heavy brass plate is grounded via four
parallel lengths of #6 cable, one going down each leg of the
table, and connecting to 1/8-inch alumnium plate screwed down
below the capacitor shelf, about one inch from the floor. This
aluminum plate acts as a small counterpoise and gives the
illusion to the coil that true ground is directly beneath it.

The counterpoise is connected with several sections of ground
strap to an electrically isolated hydraulic car lift control just
outside the garage door. This ground is better than the one used
by Tesla in Colorado Springs.
As I understand it, connecting the plate to an actual ground is
not necessary if you are using a low power coil and need portability.

Feel free to correct me, as I am only relaying what I read, 
not what I have done.