Here is my recommendation for managing the stepper motor
and its cable:
Make the loading coil out of hollow tubing. Drill a
hole in the center of the parasitic element and run the
motor wires through this hole and inside the
element out to the loading coil. Then route them
INSIDE the coil tubing. At the outer end of the
coil, again run them inside the element until reaching
the motor. It is not necessary to have high voltage
insulation at the motor or in the wiring.
If the driven element is grounded at the center
(ie "plumber's delight construction), you can do
the same thing there. If it is driven conventionally with
insulators at the center, then you need to wrap the
motor wires around toroids (acting as common mode chokes)
at the drive point of the element.
The shield of the motor wiring cable should be bonded to
the element at each end of the coil, and also at the
feedpoint and at the stepper motor.
The stepper motor will have high RF voltage on it, but
it be like a bird landing on a high tension line, and
not be affected by it.
Al Williams wrote:
> Has anyone tried modifying a Steppir Monstr with putting a loading coil in
> each side of the feedpoint (with relay to switch the loading coil in or out)?
> According to my calculations, some 20' of the tape on each side could be
> used at 4 mhz and then extended to the full length to resonate the element at
> 3.5 mhz. Or possibly some linear loading plus a smaller loading coil?
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