Tap tunable secondary

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

Original poster: "Terry Fritz" <twftesla-at-qwest-dot-net>

Hi All,

I am having problems tuning my CW coil.  It is run off a variable frequency
900 watt, 325 to 375 kHz, industrial plasma power supply.  I can wind
matching transformers on big 3C8 cores to fix input impedances, but the
frequency is a problem.  It has a master oscillator frequency control so it
does not track with fancy feedback, PLLs or anything like that.  But I can
adjust the frequency by hand.

The problem is the secondary frequency.  If I place different top loads on
it (like the power arc tonight) It tends to drop the optimal resonant
frequency too low and I can't get to the optimal frequency given the power
supply's range.

So I was thinking of making a new secondary with tap points on it so it
could be taped at different frequencies.  About 5 inches on one end will
have a bunch of wire loops coming out.  I don't know if it would be best to
put these taps at the top or bottom of the coil.  I am worried about
autotransformer action and other problems with the unused windings.  

Any thoughts on this are welcome.  I don't remember anything like this
being discussed before but maybe the long time tube coilers have run into
this and have some ideas.  I want to pump the full 900 watts forward (plus
250 reflected if needed) into a power arc to see if I can make the sparks
Richie got.

Cheers,

	Terry