[TCML] VTTC-tuning. John got me started ;-)

[Dr. John W. Gudenas]

Hi Bart
No, I haven't looked into this at all, but it is now on the list of  
"Things to check out."
My guess is that as long as you operate in the frequency spectrum the  
tube was designed for it won,t play a major role, however I  don't  
know and I certainly intend to check it out.

I have no doubt that spark loading impedance is a prime factor.  Yes,  
everything you said has possibilities and needs to be explored.
Good thoughts!
Thanks
John W. G.


John W. Gudenas, Ph.D.
Professor of Computer Science


On Apr 4, 2009, at 2:07 PM, bartb wrote:

> Hi Dr. John,
>
> Have you looked into the Miller effect? The plate to grid  
> capacitance is low in the pF's, but as the tubes are usually  
> triodes?? Probably still far to small to make a big difference on  
> the primary, however, it seems it would effect maybe some drift in  
> the tubes frequency response and the tube would vary differently  
> depending on secondary characteristics (int/ext C). I guess what I'm  
> trying to say is that maybe the slight changes in for example the  
> top terminal C is mainly affecting the frequency response of the  
> tube. I would think spark loading impedance is a major factor when  
> tuning and it would appear although resonance is important of  
> course, in a VTTC, the tubes frequency response is affected by the  
> those sparks and slight other changes in C, and tuning is a means of  
> really getting the tube itself to respond well.
>
> Just thoughts, no experience here.
> Take care,
> Bart
>
> Dr. John W. Gudenas wrote:
>> Every tube has a set of characteristics that are defined by the  
>> maker usually referred as the "characteristic curves".  Fortunately  
>> for our common transmitting triodes this operating data is all  
>> readily available. Output impedance is an important issue for  
>> optimal performance. For example, consider an audio amp that  
>> matches to 8 ohm speakers. If you use 16 ohm speakers you will  
>> still hear sound but loose a lot of power.
>
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