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Re: Singing like a banshee
Hi Chip and all,
Your comment about modulating coils and the FCC
caught my eye. I'm afraid I have some bad news.
> When I first started getting into tesla coils, I called the FCC.
> The guy didn't know much about them, but the one point he made that
> was clear was that modulating a coil (and thus any output RF waves)
> is illegal.
All coils emit RF, period. Just how much depends on the quality of
the ground, size of the coil (length in particular) and power level
(and probably other factors I haven't thought of as well).
Secondly, all coils designed to produce sparks can be classified
as double sideband signal generators, at least when either not
sparking or producing coronas (no arcs). Ideal quench times reduce
this to pure carrier but few people ever achieve this and it is near
impossible to achieve if the system is not arcing to an earthed
object. Moreover, in an ideally quenched disruptive system, the
carrier is not a constant amplitude either but a decrementing
wavetrain (AM in a sense). Additionally, the output, as the secondary
load is varied and the gap is not optimally quenched, is broadband
(all over the place - FM).
Thirdly, disruptive discharge coils (cap and gap) could be
considered modulated in a sense (the mode effectively being
interrupted carrier or CW in amateur terms).
The only saving graces are that we don't hook antennas to them
(although a poor ground can certainly act like one) and we do every-
thing we can to minimize radiation (want sparks). Those operating
coils not producing sparks are the worst radiators as can be evidenced
by lighting fluoro/neon lamps at considerable distances. You can
achieve the same effect by wandering under a radio mast waving a
fluoro lamp around.
Just thought I'd better put this thing in perspective.
Malcolm