Re: 811A any good?

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

Original poster: "by way of Terry Fritz <twftesla-at-uswest-dot-net>" <FutureT-at-aol-dot-com>

In a message dated 1/25/01 1:50:54 PM Eastern Standard Time, tesla-at-pupman-dot-com 
writes:

> I suspect our friend Terman would say you can squeeze a fair
>  bit more under low duty cycle operation, e.g. ten
>  microseconds on, ten milliseconds off.  Is that what John
>  Freau does with his massive 833 coils?  I currently have a
>  pair of 813s awaiting similar treatment as and when I get
>  the time.  I anticipate 750W out (cw) from the pair with any
>  luck. But no idea when I'll get the proverbial round tuit.
>  It may be some time.
>  
>  Dunckx

Dunckx,

I've often run the 833A coils using normal raw ac on the plates,
but sometimes I use the pulsed staccato technique to skip
some positive ac half cycles.  I do try to keep the grid drive
strong, and the bias highly negative to keep the tube conduction
angle small.  I deliberately use an excessive plate voltage of 5kVAC 
on the plate for good efficiency.  Even higher voltages tend to arc inside
the tube.

I got a 16" spark from a single 813, but it probably can be
pushed further even with normal raw ac.

John Freau