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Re: VTTC output

Original poster: "Herwig Roscher by way of Terry Fritz <twftesla-at-uswest-dot-net>" <herwig.roscher-at-gmx.de>

Ed Phillips wrote:
> You didn't mention plate current


- At full power it was 350 mA -at- Vp = 9000 Vdc and Vg2 = 1000 V. 
The plate remained at a middle red color.

> what was the net power input?
- I'm using a 3 phase tranni and haven't got a 3 phase wattmeter. 
So I don't know the net input power.

> what is the operating frequency
- It's around 200 kHz

> are you sure primary and secondary tune to the same 
- Yes I am. First I had some problems to understand frequency 
splitting, but with the assistance of Bert Hickman I found the 
correct tuning procedure.

> Have you played with the coupling?
- I've changed the distance between the lowermost turn of the 
primary and the lowermost turn of the secondary from +45 mm 
(secondary above primary) to -15 mm (secondary below primary). 
Neither the voltage across the 5.1 Ohm resistor, which I've 
connected between the base of the secondary and rf ground, nor 
the visible shape of the brush changed. Below +30 mm the 
waveshape, which was nearly pure sinusodial before, started to 
become more and more distorted. Do you have an explanation for 

In general I was rather surprised to find the system to react so 
- Varying the coupling (within limits of course) seems not to 
change anything.
- Plate current becomes larger as screen grid voltage is increased. 
The plate becomes a little bit more red, but that's it. Nearly no 
increase of brush size.
- The only thing which influenced the brush size very much, was an 
increased tank circuit impedance.

I assume that the reason is the large (in comparison to triodes) 
plate impedance of my tetrode. Do you agree?