Interference-SSTC

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

Original poster: "by way of Terry Fritz <twftesla-at-qwest-dot-net>" <Kchdlh-at-aol-dot-com>

A further observation about Matthew Smith's 400 KHz coil is in order:  Not only
is ~400 KHz a "dangerous" frequency (near the 455 KHz I.F.) but it is also
pretty high in terms of getting [Tesla-coil, garden-variety] power-transistor
circuits to operate efficiently.  At 400 KHz, 1 cycle of excitation occurs in
2.5 microseconds, 1/2 cycle in 1.25 us.  That means that one's power
transistor(s) have to fully switch on & off in 1.25 us.  It could well be that,
because of stray capacitances, Miller effect, etc., switching times could eat
up a lot of that 1.25 us unless one is an rf expert (which I am not--& I've had
enough trouble at 140 KHz).  Thus, a good fraction of the power input could be
lost in the transistors during their switching-times.

In addition, any circuit that operates efficiently at 400 KHz may want to
oscillate at a bunch of other frequencies as well.  Some of my circuits surely
did.  It might make for less trouble all around to make a new, larger,
secondary to operate at a substantially lower frequency.

Ken Herrick