Re: FCC Regs

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

Original poster: "Ed Phillips by way of Terry Fritz <twftesla-at-qwest-dot-net>" <evp-at-pacbell-dot-net>

Tesla list wrote:
> 
> Original poster: "Jim Lux by way of Terry Fritz <twftesla-at-qwest-dot-net>"
<jimlux-at-earthlink-dot-net>
> 
> >
> > I'm lucky. I only have a handful of neighbors within a square
> > mile. Closest one is an acre away, so not too concerned with
> > interference there. But local airport is a couple of miles away
> > and I've heard that the hair stands up on the back of their neck
> > when the noise comes up on the radio. They still use AM you
> > know.
> 
> Probably no issue then...   Harmonic content at 100 MHz for aviation could
> be a problem, because the TC is about the right size to be a decent antenna.
> You'd probably want to make sure you've got good filtering on the wires from
> HV transformer to tank so you don't propagate that way.  The tank itself can
> have parasitic oscillations when the gap fires. The frequency of these
> parasitics is not necessarily related to the TC frequency (i.e. it's not a
> harmonic, but a VHF oscillation in the gap and the wires connecting to it,
> much like Heinrich Hertz' original transmitter)


	I wouldn't call the VHF oscillations parasitices, but just excitation
of another resonant circuit in the coil.  Same difference, though,
plenty of real VHF radation possible.


> Empricism is probably the best way to find out... Get a 2 meter HT out,
> unsquelch it and look at the signal strength it sees with no carrier. Fire
> up the coil and see if it changes.  Do this 50-60 feet away so you're out of
> the near field.  Or, if you know someone who has an aviation band receiver,
> try that...
> 
> Or, of course, if you have it, a calibrated antenna and spectrum analyzer
> will do a dandy job...
> 
> >
> > --
> > 73 de Steve

	Thought I'd mention something of my own experience.  The only coil I
have running now has a 3.2" diameter x 15" long secondary with 12" x 3"
toroidal top load; the operating frequency is about 320 kHz..  It gives
24 to 30 inch sparks when excited by a 12 kV, 60 ma transformer (not
necessarily good performance, but can't stand any thing longer in the
place it is run.  Anyhow, when it is running I get surprisingly little
broadcast interference on a receiver about 50 feet away, and connected
to the same power line.  I can hear all of the local stations without
problems, and on many of them (for example, KNX on 1070 kHz and running
about 10 kW daytime at a distance of 30 miles) there is no discernible
interference.  While all of this is going on the sound of the open gap
is audible for a couple of hundred feet.  When I muffle the gap things
are pretty quiet.  There is visible TV interference on the low-band
channels, but not enough to be bothersome and doubt if the average
unsophisticated viewer would pay any attention to it.  TV antenna is
about 60 feet away.

Ed