Re: remote location of NSTs - away from coil base?

["Tesla list" <tesla@xxxxxxxxxx>]

Original poster: Vardan <vardan01@xxxxxxxxxxxxxxxxxxxxxxx>

Hi,

At 10:53 AM 9/1/2006, you wrote:
> ....
>
> Now we get to my question.  Someone, I think maybe Terry, told me
> once that doing this (as opposed to leaving the NST that coil) can
> cause resonance problems that would kill the NST secondary winding -
> something about stray capacitance in the HV leads going to the coil?
>
> I have some questions about this, and a certain amount of skepticism:
>
> 1) wouldn't the primary capacitance swamp any stray lead capacitance,
> making it rather moot?

I don't think it is normally a problem.  A 15/30 NST has a resonant 
capacitor size at 5.3nF.  For neon sign installation they have to be 
a bit careful of the wiring so the capacitance from the leads to 
ground does not get near that.  But that is really only if the leads 
get very long inside a metal cased sign.  For say a 9/120 the 37.5nF 
resonant capacitance is so high one should never reach it no matter 
what the wiring is.


> 2) wouldn't the resistors in the NST "Terry filter" tend to kill any
> resonance?

No.  The impedance of a 15/30 is 500,000 ohms.  The 1K resistors 
don't matter there.  They are too small to damp anything.


> 3) Has anyone else used their NST remotely away from the coil and had
> either problems you were able to trace to this issue, or no problems?
> (either data point would be useful)

I think the only way to run into trouble is to maybe use something 
like a very long run of RG-8 coax where the cable capacitance becomes 
a big factor with a high impedance NST with a low resonant capacitance size.

Maybe others know more on this too??

Cheers,

        Terry



> Thanks in advance,
>  - Bill Lemieux,
>         Denver, Colorado, USA