RE: More Urban coiling concerns

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

Original poster: "Terry Fritz" <twftesla-at-qwest-dot-net>

Hi Gary,

"I" just put line filters in the way they are labeled, but see Gary Lau's
page at:

http://people.ne.mediaone-dot-net/lau/tesla/emifilter.htm

"I" suspect you won't go wrong either way...

You may want to have a ground plane under the coil.  This is simple a
conductive metal sheet (like aluminum foil) under the coil that is attached
to the RF ground.  Coil currents tend to want to circle back to the ground
so having a good ground plane under the coil will help reduce interference.
 Split it down the center so it does not act like a shorted turn.  Some
nice electric field plots are at:

http://hot-streamer-dot-com/andrewb/

These show the voltage fields around a coil.

A grounded wire grill between the audience an the coil will vastly reduce
noise getting to the people.  Chicken wire or even 6 inch spaced magnet
wire will do wonders to stop the electric fields from messing with cameras
and such.  But that may almost be overkill.  This screen should be
connected by it's own wire back to the good ground.

Pacemaker wearers and other people that have vital medical devices have
been instructed by their doctors about electrical devices.  You should
mention this or have a sign that says this is a high power electrical
device and pacemaker wearers should take note.  With a modest coil like
yours there is no danger but you should let them know.  You can check the
archives at www.pupman-dot-com for "pacemaker" and probably find out much more
than you ever wanted to know about this :-))

You may want to use an AM radio to "sniff" around the coil for interference
to see if there are any holes.

If you are going to arc the coil to ground, I would put a big resistor in
the ground path.  Directly discharging the toroid causes some pretty big
currents.  A resistor will vastly reduce these currents and vastly reduce
EMI.  I have some big 200000 ohm foot long wire wound puppys that would
work.  Let me know if you want one (free :-)).

You may want to check around the area of the coil for cable TV, phone, and
AC wiring that may be hiding nearby.

The use of big ferrite cores, like DigiKey sells, significantly reduces
spark gap electrical noise.  Just put them (as many as you want) on the
primary wiring near the actual spark or other place in the primary loop.
That is DigiKey:

http://info.digikey-dot-com/T012/V4/389.pdf

Spark gaps make a lot of high frequency hash that these ferrites will
really knock down.  I like the 240-2081-ND big tubular beads.  The big
clamp ons look great too...

Sounds like your coil will be extremely friendly for your neighbors and
such. :-))

Cheers,

	Terry


At 02:48 PM 6/11/2001 -0400, you wrote:
>Assume I wish to use a 350w 3.5" x15" table top coil in a theatre space in a
>basement where the closet person will be about 10 feet. It operates on
>dedicated ac line from the street, but there is an electronic dimmer device
>on the mains (everything else is non-electronic) The device will arc
>directly from the toroid to the rf ground, a 6-8" distance. The NSF is
>protected by MOVs,  500 pf caps, and a safety gap to ground as well as  500
>ohm/100w resistors and small chokes in front of the tank circuit, much like
>Terry's . The primary cap has a safety gap as well. The SG is the tube-type
>stationary SG. 
>
>My issue here is that I wan to protect the audience (hearing aids, who
>knows, maybe a pacemaker)  and any electronic equipment that may be nearby
>from RF interference. I will create an rf ground 20 feet away via a 4 inch
>metal storm drain. I would ground everything from the NST to the secondary
>to that as well as a metal plate under the coil and chick wire back drop.  
>
>I will  install MOVs across the NSF primary hot and neutral to ground as
>well. 
>
>Now, I get confused on the correct use of EMIs between the variac and the
>NSF. I have read everything from normal install, back wards install, two in
>series with one front and one back. I have also read that the EMI should
>ground to rf (which I don't like) or to the mains ground, or to another
>ground that is not the mains or the rf (intriguing, and very possible where
>I am located). 
>
>So, how much rf does a modest unit like this generate? Over what distances?
>How can one tell (is an am radio sufficient), and how much difference does
>it make that it will arc directly to ground and not be permitted to freely
>produce streamer? How much rf is generated by the SG? How effective is an
>rf-grounded metal shield over it? 
>
>Any advice welcomed.
>
>Gary
>
> -----Original Message-----
>From: 	Tesla list [mailto:tesla-at-pupman-dot-com] 
>Sent:	Monday, June 11, 2001 2:12 PM
>To:	tesla-at-pupman-dot-com
>Subject:	Re: Garage door opener protection
>
>Original poster: "Terry Fritz" <twftesla-at-qwest-dot-net>
>
>Hi Steve,
>
>Depending on exactly how your opener is designed, one can often fairly
>easily
>remove the electronic PC board from them.  The connections to the board are
>usually connectors or connectors could be added.  Then you could just remove
>the sensitive electronics board when you run your coil.
>
>One should also look around for telephone, cable TV, and lawn sprinkler
>stuff
>in the garage also.  Good idea to remove pressurized cans and flammable
>stuff
>like the lawn mower gas can too...
>
>Cheers,
>
>        Terry
>
>
>At 09:16 PM 6/10/2001 -0700, you wrote: 
>>
>> I am in the process of buiding a pole transformer powered coil
>theoretically
>> capable of 8 foot arcs. I would like to run this coil at perhaps partial
>> power in my garage at times. Like many people, I have a garage door
>opener.
>> Is there any advice on how to protect the opener from damage? The only
>idea
>> that I have is to build a grounded Faraday cage around it and unplug its
>> power cord. The Faraday cage will take care of the electric field but what
>> about the magnetic field?
>
>
>