Re: New VTTC (fwd)

["Tesla list" <tesla@xxxxxxxxxx>]

---------- Forwarded message ----------
Date: Sun, 05 Aug 2007 16:12:17 -0700
From: Ed Phillips <evp@xxxxxxxxxxx>
To: Tesla list <tesla@xxxxxxxxxx>
Subject: Re: New VTTC (fwd)

Tesla list wrote:

>---------- Forwarded message ----------
>Date: Sun, 5 Aug 2007 18:08:27 EDT
>From: Mddeming@xxxxxxx
>To: tesla@xxxxxxxxxx
>Subject: Re: New VTTC (fwd)
>
>Hi All,
> 
>Has anyone tried designing an optimal VTTC based on the tubes  
>characteristics and design parameters or is that a long dead art, and now  it's all mimic, 
>cut & try, and anything that doesn't blow up or melt is good  enough? Maybe I 
>missed something, but I have not seen any references to theory  or design 
>applied to the oscillator, like the detailed theory and  design applied to the coil 
>itself. (javatc etc.)
> 
>Any old-timers know what I'm talking about?
> 
>Matt D.
>
    Designing a Class C amplifier to drive a resonant load like a TC 
would be a straight forward procedure using conventional design 
techniques which can be found in text and hand books.  The designer 
would have to guess at the load impedance somehow or other; of the load 
were resistive the job is simple and should work as predicted on the 
first try .  On the other hand, designing an oscillator to drive a 
resonant load which changes tuning and impedance with streamer formation 
is pretty near impossible.  People have encountered the same problem 
trying to design oscillators to drive cyclotrons.  Somewhere or other I 
have a paper written by a guy at UCLA which analyzes the problem.  
Haven't looked at it for years but was kind of discouraged at what I 
read.  The probability of the oscillator switching from one mode to 
another [one of which would "work" and the other might cause excessive 
plate dissipation] is high and hard to control.

    My last VTTC was built in High School over 60 years ago.  It worked 
- sort of.  Low power, about 50 watts, and god knows what the frequency 
might have been.  Were I to start over I'd seriously consider using the 
power amplifier approach with a separate oscillator to drive the "final 
amplifier".  Even this would require some cut and try to get the tuning 
and coupling to the coil set right but having a stable drive level and 
frequency for the amplifier would make things a lot easier.  I think 
about this once in a while because I have suitable tubes and HV power 
transformers but can never work up the ambition.

Ed

Ed