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Re: Our friend the FCC



Tesla List wrote:
> 
> Original Poster: Hollmike-at-aol-dot-com
> 
> Greg,
>     I have a copy of the frequency allocation chart put out by the FCC.  It
> shows several ranges of frequencies that are used by amature radio buffs
that
> are probably ok to run a TC at.

The amateur radio bands are probably the worst place to emit any extra
energy. They are fairly crowded and there are a lot of people with
nothing better to do than track down sources of interference.  For that
matter, the lowest ham band is the 160m band (1.8 MHz) which would be
pretty high frequency for a fundamental (however, see my comments on
harmonics, below).

>  There are also several Maritime frequencies
> that might be ok if you are nowhere near the ocean(don't know for sure
> though). 

At medium frequencies, propagation distances of thousands of miles are
quite easy to achieve, so not being near the ocean isn't particularly
significant.

The lower frequencies (say 100-400 kHz) is a air/marine navigation band,
used for low power beacons. Emitting broadband power in that band will
not win you any friends particularly if you are out in the boonies
(Alaska, northern Canada, etc.), where these nondirectional beacons are
heavily used.

>     The only "for sure" frequencies that you would not have a problem
with is
> from 0 to 10kHz.  For some reason this is no man's land and the FCC would
not
> bother you if your coil ran in this region.

However, you'd better not have any emissions at 10.3 kHz and around
there, which is the Omega navigation band.  Propagation is fairly good
at those frequencies, but it is hard to radiate significant power when
your antenna is a very small fraction of a wavelength.  For instance,
the submarine ELF transmitter in Wisconsin(?) puts many, many kilowatts
into the 5km x5km antenna array (which is actually buried, because it
makes no difference in performance) to actually radiate a small fraction
of a watt. The rest of the power just heats up the ground (a very little
bit).



Also, any system like a TC that uses a pulsed waveform is going to have
significant harmonic output power, so even if your fundamental resonance
were down at 10 kHz, you'd be putting out a bunch of power at 20, 30,
40, 50, etc.  A non-pulsed tube coil running Class A might be an
exception, but even most tube RF amplfiers (running Class AB, B, or C)
require a fair amount of filtering to get rid of the harmonics. Most
tube TC's run Class C, and have plenty of harmonics in their output.