Re: BIG counterpoise

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

Original poster: "Paul Nicholson by way of Terry Fritz <twftesla-at-qwest-dot-net>" <paul-at-abelian.demon.co.uk>

Weazle wrote:

 > Why not try a system of radials?  Ideally they should be one-
 > quarter wavelength long at your coil's operating frequency...

Only if you want a good match to the impedance of free space
and thus radiate efficiently.  For a TC, all that is necessary
is a reasonably low resistance collector for the E-flux
emanating from the secondary and topload.  Connection to the
actual 'earth' is not necessary.

As Jim suggests, use Terry's E-Tesla6 to plot the E-field
to get a feel for the area of ground that you need to cover
with chicken wire or foil.   Typically, a good portion of the
field lands within the radius of a topload-height.

I use a bunch of 'rugs', each an 8' by 4' foil sandwich between
sheets of builder's polyethylene.  Each has a terminal in a
corner, I just lay them out around the base of the coil and
clip them all to the sec base with croc leads for a total
counterpoise area of 25 sq metres.  Insulated from each other
and connected as a 'star', there's no opportunity for large
eddy loops. Running CW I don't get ground strikes, so no probs
with the poly.  Chicken wire is probably more robust in that
respect.

Remember, the purpose of the 'ground' is to collect the E field
from the coil and topload, so there's not much point in
hammering down to the bedrock or connecting to a ton of
metal dozens of yards away.  Quite a different kettle of fish
to that of a radiating antenna (in which long lengths are
necessary in order to achieve a non-negligible radiation
resistance).
--
Paul Nicholson
--