For those of you who lack the necessary technical acumen
to qualify for a Ham Radio licence, the issue is two-fold....
A variable tapping point _TOGETHER WITH_ a variable inductance
require two independently variables, but the roller-coaster
provides you with only one.

"Reg Edwards" wrote in message
...
Presumably the roller coaster could be used for
a vari-tap, but then that means that the whole coil
will always be in circuit.
You've never seen a roller coaster I take it.
He just loves looking for problems where none exist.