Re: VTTC provisional results

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

Original poster: "Ed Phillips by way of Terry Fritz <twftesla-at-uswest-dot-net>" <evp-at-pacbell-dot-net>

Tesla list wrote:
> 
> Original poster: "Herwig Roscher by way of Terry Fritz
<twftesla-at-uswest-dot-net>" <herwig.roscher-at-gmx.de>
> 
> Ed Phillips wrote:
> 
> >  In a coupled-resonator system such as a TC, the
> "transformation ratio" is no indication of the voltage rise you might
> expect.
> 
> Ed,
> 
> Thank you for "enlightning" me again.
> 
> > Have you tried varying the spacing between primary and
> secondary while keeping things in tune?
> - Yes. I made a series of tests, varying the spacing = coupling
> between  primary and secondary coil in 1/2" steps and looking for
> best results while varying the tank cap.

	As far as I know that's exactly what you should be doing.

> The goal was to make the coupling rather tight by engaging as
> many turns *at the lower end* of the secondary coil, because this
> part was wound with a thicker wire. I found that there was an
> optimum, but the point was not very sensitive.

	I'm not sure whether that is the correct way to make adjustments. 
Perhaps someone else can comment?  Not surprised the point wasn't
sensitive.

> > and once you have determined that you've done all you can.
> - I assume that this is valid for a definite primary coil. Could coils
> with other impedances lead to different outputs? What's the way to
> go?
> 
> Regards,
> 
> Herwig
> 

Herwig:

	Think you have done about as much as you can to increase the power. 
You could play with increasing the feedback and/or reducing the grid
bias resistor, but all that might do is just make the tube hotter.

	May some of the "PRO'S"  will have something more to suggest, as I
can't and since I'm not building VTTC's, probably have no right to make
suggestions.  I have plenty of experience with tube transmitters, and
think the words I've given you are sensible.

	One thought which you probably won't want to bother with.  You could
use a separate oscillator to drive the tube which drives the coil.  That
way you could adjust the frequency and leave it alone while you try
different coupling values and primary tuning.  I'm not sure you'll do
any better that way, though.

Good luck and keep the reports coming!

Ed