Re: Noisy Gaps x2 RE: Halloween Coiling and the FCC

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

Original poster: "Paul Benham by way of Terry Fritz <twftesla-at-qwest-dot-net>" <paulb-at-woodanddouglas.co.uk>

I have been looking at the interference caused by the gap - static in my
case.  It consists of 1/4 inch tungsten mounted in aluminium blocks.  There
are 3 gaps in series.  Power input is around 200W for the tests that I have
been carrying out.

I have found that fitting chokes, resistors and ferrite clamps in the PSU
leads close to the spark gap helps greatly in reducing down radiated
emissions at low frequencies, say up to 30MHz,  but actually makes the
radiation up at UHF in the TV band here in the UK worse(470-860MHz).  I then
fitted the spark gap in a biscuit tin with a fan and ventilation grills and
it has made a very big improvement in interference in the UHF band.  I am
still working on it so the design is not finalised.  At the moment the
interference on the TV is hardly noticeable when running within 20 feet of
the TV indoors.

Of course solving interference from the gap on its own is one thing, solving
it when you then connect the primary and MMC capacitors that are outside the
biscuit tin is quite another!  It may be that I have been wasting my time
with the tin enclosure, but it has been interesting.

Cheers,

Paul Benham.

----- Original Message -----
From: "Tesla list" <tesla-at-pupman-dot-com>
To: <tesla-at-pupman-dot-com>
Sent: Thursday, October 03, 2002 11:24 PM
Subject: Noisy Gaps x2 RE: Halloween Coiling and the FCC


> Original poster: "Ken Stevens by way of Terry Fritz <twftesla-at-qwest-dot-net>"
<bluewaterdiver-at-earthlink-dot-net>
>
> If most of the "noise" is coming from the gap, has anyone done any
> significant looks into a Faraday cage, or metal enclosure, over the gap?
>
> And with that, what has anyone found to be the least obnoxious (read
> quietest) type of gap? Enclosed or Open? Static or RSG? What???
>
> I live in an up-scale part of town and radio noise aside, most everyone
> has cable or dishes, the audible noise is sure to annoy a couple of
> neighbors.
>
> Anyone had to deal with unreasonable neighbors and what steps solved the
> problems. It's not a problem yet, as I'm still under construction, but
> I'm sure it will be.
>
> Thanks,
>
> Ken
>
>
> -----Original Message-----
> From: Tesla list [mailto:tesla-at-pupman-dot-com]
> Sent: Thursday, October 03, 2002 11:46 AM
> To: tesla-at-pupman-dot-com
> Subject: Re: Halloween Coiling and the FCC
>
> Original poster: "Winston Krutsch by way of Terry Fritz
> <twftesla-at-qwest-dot-net>" <u236-at-earthlink-dot-net>
>
> Hi Dan, All,
>
> This sounds bad, since I have an airport about 4 miles from my
> house...  But, is the LF radiation from the coil of much concern to the
> airport?  I think some navigation beacons run at low frequency, but
> maybe I'm wrong?
>
> I think the parasitic oscillations in the tank circuit that run
> into
> the multi-MHz and 100 MHz range are of more concern, since they are in
> communications bands (I think).  Has anyone detected these VHF range
> signals at any significant distance from a running coil?  I know much of
> the VHF hash comes from the sparkgap itself.  The same interference is
> caused by electric drills, saws, and other devices with brush-type
> motors, and people don't usually don't care about it.  Also, I don't
> think that airports have much of a problem with it.
>
> I'm just wondering if my situation really warrants caution from
> a
> radiated RF standpoint.  I run my coil outside often, and even with a
> crummy RF ground, and no line filters, my mother reports only minor TV
> interference (when the coil is in tune).  When out of tune, the TV
> wasn't watchable :-0.
>
> Thanks,
> Winston K.
>
> Tesla list wrote:
> >
> > Original poster: "by way of Terry Fritz <twftesla-at-qwest-dot-net>"
> <dhmccauley-at-spacecatlighting-dot-com>
> >
> > I know a lot of people here claim that tesla coils are quite "lousy"
> at
> > being antennas and all that, but they throw a whole huge amount of RF
> hash
> > out in the atmosphere especially when run outside.  Especially in a
> very
> > urbanized area, you may attract the attention of other "listens"
> especially
> > if near an airport, etc...
> >
> > My very good friend Lou, a seasoned ham operator, made a bet with me.
> He
> > claimed he could hear my tesla coil with his antennas at 20 miles away
> > during operation.  Since "the group" here previously claimed that
> tesla
> > coils were lousy radiators, i figured i had that bet won.  Anyways, i
> set my
> > coil up outside and he and my friend were at his house where all his
> ham
> > equipment was set-up.  We then synchronized our watches and he
> informed me
> > to key at random 3 short pulses.  This was accomplished by quickly
> turning
> > off power to my 15kv/60mA NST.  He then told me to do this at random
> > intervals for the next half hour and that he would record the exact
> time he
> > received them.
> >
> > Well, sure enough he got almost all the transmissions.  He also picked
> up to
> > the 3rd harmonics of the signal as well which were much fainter no
> less, but
> > still detectable.
> >
> > We then reversed roles and repeated the experiment.  Voila.  Same
> results.
> > And it was blatantly obvious when that thing was on.
> >
> > I never would have thought it could be such an efficient radiator!!!!
> I'm
> > convinced now!!!!
> >
> > HOWEVER, it still wouldn't stop me from firing my coil up outside.
> I'm
> > going to do the same.  Of course, halloween is the perfect excuse to
> run the
> > coil outside!!!!
> >
> > Dan
> >
>
>
>
>
>
>
>
>
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