Comments on Magnifiers
Some comments, suggestions, and tips on magnifiers:
This information is related to some of the data posted by Rich, Terry, and
The driver coil acts as a powerful current source to supply the base of the
resonator coil. The current is in phase at both bottom and top end of this
coil. The resonator coil also has current of the same phase at both bottom
and top. The current in the resonator coil does decrease in height as you
go up the coil. This resonator is acting like a single lumped inductor as
noted by Terry.
As Rich Hull noted in some posts the resonator coil can be either solid
magnet wire or Litz wire or stranded --- it doesn't matter very much in
this coil and that is why the resonator coils can be from very fine magnet
wire with fairly high DC resistance. It is not critical here.
An exception is in the driver coil. This coils main function is to produce
extremely high currents and it is very important to maintain high Q factor
in this coil. A 4 or 6 AWG Litz wire would work very efficiently here as
would a fine strand welding cable. A good rule of thumb design for this
coil would be to divide it into 3 separate parts --- perhaps with small
toroid or 2 inch dia copper tubing rings on each section. The first 33.33%
of the coil would be very low resistance, the first 33 .33 % section would
be approximately 1/2 of the resistance value of the second section, and the
second section would again be 1/2 the resistance value of the top section.
Since a lot of turns are not necessary in the driver coil, the first
section could perhaps be copper tubing, second section welding cable, and
final section 4 - 6 AWG Litz wire. A large diameter is also very important
to maintain high inductance, and hence, high Q factor. A large fiberglass
tank is ideal. A good place to pick up one at reasonable cost is a
farmer's cooperative --- they use them for feed storage and herbicide
Another thought on the enormous toploads on the resonator coil. Obtain a
large toroid that is sliced or, if assembling a monster 12 to 18 x 60 - 80
inch size toroid with inexpensive dryer duct tubing, then make two of them.
Use one of these (or 1/2 of the sliced toroid) as a top piece, and then
insert a longer aluminum or screen cylinder between the two pieces. You
gain a lot of capacitance this way and only use 1/2 pieces of the toroid on
each end which reduces the overall cost. We use this screen idea on our
"Big Bruiser". The screen is a simple 3/4 inch mesh and fairly
substantially stiff in material. It is available at most any large
hardware store or farmer's cooperative (best prices). The screen is
wrapped into a circular cylinder and joined together with a weaving of
copper wire. As an example, the cylinder might be 6 feet tall with a large
wire duct type toroid on each end. An enormous amount of capacitance is
gained in this manner which allows for a very high drive on the capacitor
end of the primary side of the driver coil.
As Chuck Curran posted a good source for the air duct tubing is: Snappy,
1011-T 11th Ave., Detroit Lakes, MN, 56501. Tel is 218-847-9258.
I trust this information might be of assistance to those contemplating