RE: RF CT

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

Original poster: Thomas <tom-at-pwrcom-dot-com.au> 


 > Original poster: "J. B. Weazle McCreath" <weazle-at-hurontel.on.ca>

 > Hi Tom, Coilers,
 >
 > I've done much the same here.  I wound my own CT on a toroid core with
 > about 15 turns of hookup wire for the "secondary" and passed the heavy
 > TC secondary ground wire through the hole just once.  I then connected
 > the CT "secondary" via some small coax to an R.F. demodulator based on
 > a circuit shown in the ARRL Handbook.  The demodulator output connects
 > to my VTVM which is set for measuring AC volts.
 >
 > 73, Weazle, VE3EAR/VE3WZL
 >
 > Details of my "Hyperbaric Gap" and Tesla coil are at:
 > http://www.hurontel.on.ca/~weazle
 >

I think it was you that gave me the idea after you mentioned it briefly in
another post.

Rather than coaxial cable, I used screened twisted pair for a bit of extra
common mode rejection.

I also highly recommend using BAT85 shottkey diodes, they're cheap and only
drop 0.4V -at- 10mA.

I did some calibration with a signal generator (at my TC's Fres) this
morning. It seems full scale (no attenuation) is about 6mA.

This shows how lucky I really was, as I made my initial estimates based on
FSR of 2mA.

Question:

6mA -at- 0.45MV (guesstimate from JAVATC o/p) = 2700VA

VA (NST i/p faceplate) = 4.4A -at- 240V = 1056VA

VA (NST o/p faceplate) = 80mA -at- 11kV = 880VA

What is going on? I have a PF correction cap on the i/p to the NST. I guess
I'll have to wait until I hook up the Vac and Iac meters I just purchased to
see the real current drawn by the NST.

Tom L.