RE: diode used against RF? (fwd)

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

Original poster: "sundog" <sundog-at-timeship-dot-net> 

Hi all,

  I've run my NST's in a DC setup.  Firstly, you've got to build the strings
at *least* 2x the voltage to run it more than a second or so.  I recommend
3x as a strong minimum.  10mohm bleeders across each diode seemed to help
them live longer.  I use the 1kv1A (4007's) frum digikey.  1000 cost me
~$40, i believe.  You get a pretty ripply DC off it, but it's DC and charges
caps just fine.  For larger applications, I'd derate current to 1/2 on them,
as even on my 180ma NST farm they got warm after long runs.

 On the input side (mains) I noticed less fluctuation of the input current
than running AC, and it seemed more "well behaved" as far as current draw.
Not much less overall, just a bit smoother.  Any difference in performance?
Not really.  I think the diodes and resistors burned up some power, but not
enough to matter.  Though you eliminate reso-charging, so you can unplug
your rotary and let it spin down.  Pretty cool.

  But, I don't think these diodes are fast enough to clamp down on an RF
signal.  I still think that MOV's and a small RC network like the one Terry
Fritz designed will work best protecting your NST.  Sure, you loose a little
spark length, but if it took you 2 months to find an NST, you'll want to
protect it.

 On a PT or pig system, I don't know.  haven't got my pig to try it on yet
;) Workin on that. maybe someone else has?
												Shad


-----Original Message-----
From: Tesla list [mailto:tesla-at-pupman-dot-com]
Sent: Thursday, December 07, 2000 12:11 AM
To: tesla-at-poodle.pupman-dot-com
Subject: Re: diode used against RF? (fwd)


Original poster: Tesla List Moderator <mod1-at-poodle.pupman-dot-com>



---------- Forwarded message ----------
Date: Wed, 6 Dec 2000 23:37:58 EST
From: Pyrotrons-at-aol-dot-com
To: tesla-at-pupman-dot-com
Subject: Re: diode used against RF? (fwd)

<< i was wondering if a diode could be connected in series with the NST.
this
would rectify but wouldn't really affect the charging of the cap
there wouldn't be any frequencies from the primary circuit getting into the
secondary of the NST...has anyone tried using a diode???
any promising results?? thanks in advance.
M. Bains >>

Hi M. Bains and All.

I can almost guarantee that a *typical* diode or rectifier would immediately
fry in this application.

A string of diodes in series to is required to get the voltage rating up.
(you're not going to find a 30kV diode...the highest I've seen in a single
package is 26kV) Anyhow, if you did this then you'd just be making a DC
coil....and a number of people have done it. I don't know the overall V
rating of the diode stacks they use, but it must be pretty dang high. I know
that people have killed these expensive diode stacks, too.

I imagine the diodes would protect a transformer fairly well.....that is if
the diodes can live through it themselves. Does anyone have input as to how
well a transformer will live in a DC coil? I'm thinking a long time, as the
rectifiers won't pass current (kickbacks from the coil) when reverse biased.

I'd say it's a good thought, and it does work to my knowledge. (I know the
DC
setup works, but I'm not sure about the transformer protection idea).

Justin Hays
KC5PNP
Email: pyrotrons-at-aol-dot-com
Webpage: www.hvguy-dot-com