At 12:56 PM 01/01/2000 -0700, Steve Young wrote: 

> Hello list,
> Another scientific curiosity question:  Has anyone experimented with a sync
> RSG designed in a SPDT configuration?  By that I mean the cap is connected to
> the center pole of the gap-"switch".  The pig (or other HV transformer)
> connects to one pole, and the TC primary connects to the other pole.  There
> would thus be two gap presentations per bang.  The first presentation only
> charges the cap.  The second presentation discharges the cap into the primary
> tank, completely isolated from the power source.

"I" have never heard of this but it sounds like a very good idea!!

> This avoids putting the gap across the pig, which perhaps lets the gap run
> cooler (no 50 or 60 Hz power arc), and may lead to higher efficiency and
> better quenching.  This would also aid in keeping nasty RF out of the pig,
> and perhaps would reduce the need for RF filters.  On the other hand, the gap
> losses are now twice(?) as high per bang.  This is probably a lousy setup for
> NSTs as there is nothing to keep the NST voltage from soaring too high.

The gap losses should be the same.  The NST charging current... Oh.. I just saw
a problem.......

First I'll go on with the thought.  The gap losses are proportional to current
squared.  The NST charging current squared is 0.060^2 = 0.0036.  The primary
circuit current is probably around 10 amps RMS so 10^2 = 100.  Thus, the loss
in the "firing gap" is 100/0.0036 = 27777 times higher than the "charging"
gap.  The charging current gap resistance may be higher (and probably is) than
the firing current so the loss is higher but it should not matter...

Now that problem...  The NST can only supply say 60mA  Thus it will not charge
the cap in the time only a brief point presentation would give.  The NST needs
the full "non-firing" cycle time (about 98% of the cycle) to recharge the cap. 
Thus, your charging gap would have to be a long semicircle that would allow
current to flow all the time except when the actual firing time comes. 
Technically,  that is very possible to build but I wonder if the charging gap
would tend to blow the arc all over as it's spinning - sort of doing the
Jacob's ladder effect.  The charging gap could probably physically touch the
rotor since the current is fairly low to get around this.

You could size the primary cap so that a failed firing would not over voltage
it (as in LTR coils) or use REALLY good safety gap (properly set!! ;-)) to
protect the neon in such a system.

You have some very interesting ideas Steve!!



> If someone has tried this, please let us know the results.
> --Steve Young