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Re: Halloween Coiling and the FCC



Original poster: "Paul Nicholson by way of Terry Fritz <twftesla-at-qwest-dot-net>" <paul-at-abelian.demon.co.uk>

Boris wrote:
> Its' spark plugs generate so much short wave noise
> that even neighbours in 50 m diameter from it see
> mostly the "snow" on theirs Tvs. 

Yes, hence the use of resistive plug leads these days
on cars to reduce the Q of the lead at its resonant
frequencies.  

The spark gap in conjunction with its VHF antenna
(the primary wiring) could well be the 'brightest'
part of the coil in that part of the spectrum.  As
Paul Benham has demonstrated, it can be brought 
under control, with the added bonus of shutting off
light from the gap.

Dave Hartwick wrote:

> I KNOW that my neighbors within a substantial radius
> are aware of SOMETHING going on in my basement.

Reminds me of that movie "The 'burbs" with strange
lights and noises coming from the basement.  Do you
find your neighbours going through your garbage :)

> for clearly even the most modest coil violates at
> least some of their strictures.

I feel that the sources of excess radiation can be
identified and controlled.  We have the technology,
we should be able to make a TC no less troublesome
than a domestic power tool, I think.  We should do
this ourselves before someone does it for us.

Mark Stolz wrote:
> I couid point a pickup someone keying their 10mW 2 meter
> radio 20 miles away but would it mean anything?

Yes.  I used to work my local repeater at 40 miles on
10mW FM.  It shows that the natural background at 
VHF/UHF is much lower than at TC operating frequencies.
Therefore a few mW escaping at 200 Mhz is much more
serious than a few mW at 2Mhz or 200kHz, because it
has less to compete with in the front end of any 
receiver.  Also, most of us are surrounded by VHF/UHF
receivers of one sort or another.  For these reasons
I'd say that the VHF/UHF radiation, from the gap and
perhaps from breakout/toroid resonances, is the one
that could cause the most trouble, as opposed to 
radiation at the operating frequency and coil overtones.

A couple of tips from my ham experience:
a) don't go and poll your neighbours looking for 
interference, otherwise they'll be round every time
there's *anything* wrong with any of their domestic
electronics.  
b) make your own discrete tests, take a scanner for
a walk while a helper fires your coil. Find out if
there's a problem before your neighbours figure where
it's coming from.
c) if a problem is reported, take it seriously, fix it
right away, by not firing if necessary until you have
a cure. 

It's hard to hide ham activities, when the house nestles
under an antenna, similarly for coils with the noise, etc.
Many similarities, fortunately there's a whole toolkit of
techniques that hams use that could also be applied to coils.

Another thing. Inlet chokes may be pretty good at a few 
Mhz, but transparent at VHF.  You may need a separate
filter to trap the VHF/UHF stuff.  Ferrites and feed-through
caps.
 
And if all else fails, tell your neighbours that it's
either coiling, or you take up learning the bag pipes.
--
Paul Nicholson
--