Re: Capacitor Help

["Tesla list" <tesla@xxxxxxxxxx>]

Original poster: "MalcolmTesla" <tesla@xxxxxxxxxxxxx>

----- Original Message -----
From: "Tesla list" <tesla@xxxxxxxxxx>
To: <tesla@xxxxxxxxxx>
Sent: Saturday, December 17, 2005 2:50 PM


> Original poster: "Gerry  Reynolds" <gerryreynolds@xxxxxxxxxxxxx>
>
> Hi Malcolm,
>
> The safety gap is usually a three terminal gap.  Center terminal is
> connected directly to NST chassis. The two outer terminals connect to
> the NST bushings (if no Terry filter) or to the main gap side of the
> Terry filter if you are using one.  The purpose of the safety gap is
> to protect the NST and is adjusted with the TC primary disconnected
> from the circuit so the NST is unloaded.  One sets each side of the
> safety gap to "just not fire" with the NST at maximum voltage.

My original understanding was that the NST connected to mains ground and the
safety gap center terminal connected to RF ground with only the strike ring
and secondary coil.  That way if a streamer struck the primary coil the high
voltage would jump across the safety gap to the RF ground and leave the NST
alone.  Or does that now work unless the NST's chassis is also connected to
RF ground?
OR - is this one of those things that can be done multiple ways and I just
need to pick one?

> If you want to also set you main gap this way (really not necessary
> if you use a safety gap), then you can set it to the maximum setting
> possible (also with the TC primary disconnected) so the main gap
> fires reliably.  Dont trust physical separation measurements as the
> geometry of the gap helps determine the breakdown voltage.
>
> The main gap is a two terminal gap where as the safety gap is a three
> terminal gap.  You can think of the safety gap as really being two
> gaps one for each bushing of the NST.  If you do use a safety gap
> that is properly set, then you can experiment with the main gap
> setting and dont need to worry about setting it too wide.

Sounds good.  I will be using a safety gap.

> Regarding grounds,  most operate their TC's outside and tie the
> secondary base and strike rail to RF ground (copper rod staked in the
> ground).

That's consistant with what I've been hearing.

> The safety gap ground terminal should always be tied to the
> NST chassis directly (as short as possible since the NST is what it
> is protecting).  Many tie their NST chassis to RF ground to help keep
> noise off of the mains when the NST is located with the TC and is not
> a safety consideration.  Since you will be operating inside and dont
> have a RF ground available and the TC and NST will be inside this
> chicken wire tree cage (if I interprete what you say correctly),  you
> may want to ground the tree cage so it acts like a faraday cage.  It
> would be grounded to your "RF ground" that in turn would be grounded
> to the mains green wire.  The whole TC and NST would then be
> surrounded by a grounded cage and sparks eminating from the TC will
> probably hit the tree cage.

Humm OK.  So I should move the NST off of mains ground and tie that to the
RF ground along with the strike ring, and secondary's ground.  Then when I
fire the unit up at home I can hook up my RF ground to a copper pipe in the
ground.
However at work I'll hook up my RF ground to the large chicken wire cage
(and I'm also going to run a wire up to the over head steel beams above the
suspended ceiling).  Yet you also say for the indoor usage at work I should
join the mains ground to the RF ground.  Would this not defeat the purpose
of having the seperate RF ground and cause lots of noise to go back to the
110 mains ground?

>  I hope this wont be a fire hazard and
> I'm not sure how people would see the sparks if the cage was covered
> by tree stuff.  I may not be visualizing this correctly.

The cage was built to look like a christmas tree.  There is no other stuff
on it to catch on fire.  Well I guess there are a few glass ornaments, but
nothing flammable.

> In general, indoor operation can be done with low power TC's using a
> one ground system (green wire) and a counterpoise (a ground plane
> everything sits on with a radius at least equal to the height above
> the ground plane that the coil and topload are).  The counterpoise
> can be chicken wire, AL foil, etc.  It will be very important for
> indoor operation to NOT let the sparks hit anything that is not
> grounded directly to the base of the coil. Especially avoid hits to
> the walls and ceiling.   It will also be important to not have any
> secondary to primary hits (your strike rail should prevent
> this).  For this configuration, the NST chassis, secondary base,
> strike rail, and counterpoise are grounded to green wire.

Again, won't the RF ground interfer with the mains ground if I join them?
Maybe I should just put the RF ground (strike ring, secondary, safety gap)
to the chicken wire cage and overhead beam and not join it to the mains.
Thoughts?

> You may
> also want to make sure that any electronics plugged into the mains
> are turned off or better yet unplugged.

Humm a whole office full of computers.  I won't be able to make everyone
unplug their PCs.

Thanks
Malcolm - KC