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Re: Case ground.

Tesla List wrote:
> 
> Subscriber: knardell-at-mailhost.accesscom-dot-net Sun Jan 12 22:17:48 1997
> Date: Sun, 12 Jan 1997 17:05:44 -0600
> From: Kevin <knardell-at-mailhost.accesscom-dot-net>
> To: tesla-at-pupman-dot-com
> Subject: Re: Case ground.
> 
> >Daniel,
> >
> >There are a few reasons to tie the case to at least the RF ground:
> >
> >Since large Electrostatic fields are present betweent the toroid and its
> >surroundings, the primary needs to have a path to ground to prevent
> >electrostatic induction from inducing high ES voltages (to ground) on
> >the entire primary. Grounding the neon case "bleeds" this off.
> >
> >A pair of safety gaps should be used from each neon HV leg to the case
> >ground (and RF ground). This serves two purposes: it reduces overvolting
> >the neon's outputs, AND it provides a low-impedance path the the RF
> >ground in case you take a "hit" from the toroid to the primary. This
> >protects EACH leg, and prevents an RF flashover that otherwise would
> >find ground through your neon's secondary to the 120 VAC side... not a
> >good thing!
> >
> >There's a belief that grounding the case reduced RFI, but I'm not aware
> >of any actual before-after measurements. The first two above should be
> >reason enough...
> >
> >Safe coilin' to you!
> >
> >-- Bert --
> >
> >
> >
> Bert,
> 
> I again am having trouble with noise, I was showing my neighbor a new laser
> I just got and he said he could hear my coil running LOUD over his phone
> conversation. I have filters inline now, what else can I do? I put some
> chokes on the HV outputs of my neon and the coil stoped sparking. Why?? I
> also have a excelent rf ground, would this be a good time to pull the Neon
> case to the RF gound? My filter system is well grounded (The case) to the
> house ground as recomended by manufacturer. Any tips or hints, a faraday
> cage is out the question, I now have a coil, 2 lasers (Very big) and my
> other electronic junk in my play room, no room, money, or time to construct
> a cage.
> 
> Anything I overlook?
> 
> Thanks in advance!
> 
>                                        Regards,
>                                             Kevin Nardelle
> 
>    ********************************************
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> My main web page IS UP all TESLA
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> **********************************************

Kevin,

Tesla coils generate interference in many ways. Electric sparks, in
general, generate RF noise by "exciting" the small wiring inductances
and capacitances in your HV primary circuit. This causes the primary
wiring to "ring" at higher (VHF) frequencies. Streamers and (especially)
ground arcs also radiate at higher frequencies. Finally the coil
itself radiates RF across a rather broad spectrum - the lousier the
primary "Q", the broader the range around your center frequency. 

The 120V EMI filters you've added will only help reduce interference
that's being conducted back into your power mains through the wires. 
They won't stop radiated high-frequency noise. It sounds like your
neighbor may be picking up radiated noise on his phone. Is his phone a
regular (hard-wired) or portable? Portable phones, being radio
tranceivers, are typically much more sensitive to radiated Tesla Coil
noise.

You can reduce noise radiation somewhat by making all of the high
voltage and primary/capacitor interconnection wiring as short as
possible, by minimizing the length of wire connecting your coil to
your RF ground, and using a solid RF ground (multiple groundrods). Tie
your transformer case to the RF ground as well. If you're still running
with the cap across the transformer, this may also increase the noise
you're radiating. Anywhere you've got a pair of balanced
current-carrying wires, like those going to the primary, run them close
together and in parallel to reduce their ability to act as individual
antennas. 

Operating your coil at times when your neighbors will be unlikely to be
using the phone or watching TV will also minimize your neighbor's
aggravation. Try to get him interested in the hobby (maybe as your lab
assistant) :^) Keeping your neighbors happy is essential for you to
continue successful coiling! If the above these measures are still not
good enough, then other steps can include constructing and running the
coil in a room surrounded by grounded aluminum siding, metal
screen/sheet, firing the coil in a more remote location (perhaps off a
portable generator), or looking for another, quieter hobby - like maybe 
pyrotechnics?. :^). Unfortunately, a Faraday cage is the only way to
truly contain radiated RF. 

Using high voltage chokes may reduce coil output somewhat by impeding
the tank cap charging process. However, they shouldn't prevent the coil
from operating unless you're running with very wide gaps and were just
barely firing the gaps prior to adding the chokes. Although chokes will
help protect your neons from internal breakdown, they won't do much to
reduce
radiated HF noise. 

Any other ideas, particularly from the Hams out there??

Safe coiling to you!

-- Bert --