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Pulse Forming Networks



Has anyone on the list had any experience of using a commercial pulse
forming network to drive a Tesla coil?

I have recently acquired one of these, along with a number of other bits
and pieces from a dismantled Cossor wind-finding Radar.
I have copies of the radars circuit diagrams, but I'm missing some vital
bits like the 15kV above deck heater transformers for the rectifiers and
Thyratron!

The PFN is a Dubillier type DN350. It has 4 terminals marked T0,T1,T2,T3
  There are 2 (measured) 25nF capacitances from T0 to T1 and T2/T3  The
circuit diag. also shows some linked inductances, though I dont know
what value these are.

Anyway, temptation got the better of me, and I tried it in place of my
primary cap! (home brew rolled PE 16nf)
I wired it so that the capacitances were in series giving about 12.5nF
After retuning I got over 40" of arc from the 10kv 50ma OBIT I'm
experimenting with at the moment.
The coil ran very smoothly on the PFN with about 40% more output than
any of my other caps.
I'm not too sure what "resonant charging" is I see referred to on the
list, but is it possible that the built in inductances have something to
do with this increase in output?
I dont know what the voltage rating is for the PFN but it pulsed the
Magnetron through a weird looking pulse tranny at 28kV peak pulse!
If I could get the whole radar modulator working again, (I have most of
the bits and it was working ok prior to decommissioning) and work out
how to match this into a TC there would be the possibility to have full
electronic control of pulse repetition frequency and pulse width. (very
useful for research purposes!)

Anyone out there had any experience of this sort of stuff?

                       Thanks  Martin Dale, G6ABU

ps  You would never get a TC licensed in the UK!  The very mention of
sparks and RF would make the average RIS officer foam at the mouth!
Before anyone asks, mine's in a Faraday cage!