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Registered Member #543
Joined: Tue Feb 20 2007, 04:26PM
Location: UK
Posts: 4992
The VTTC circuits that I have seen on this forum are all of the type known as an Armstrong Oscillator, the first - and simplest - valve oscillator to have been discovered (by Edwin Armstrong just after the Great War)
There are plenty of explanations of the basic operation of the Armstrong Oscillator on the web.
Registered Member #1497
Joined: Thu May 22 2008, 05:24AM
Location: Toronto, Ontario, Canada
Posts: 801
Well there have been alot of threads recently about VTTC's, I dunno, some odd nostalgia virus going around. As for actually building one it doesn't seem any more expensive than a SSTC since the most basic tube apparently is the 811A and can go as cheap as $20...
Registered Member #152
Joined: Sun Feb 12 2006, 03:36PM
Location: Czech Rep.
Posts: 3384
aonomus wrote ...
As for actually building one it doesn't seem any more expensive than a SSTC since the most basic tube apparently is the 811A and can go as cheap as $20...
Well, I built my first SSTC with two $1 FETs and other parts were reused/scavenged. It gave a 20cm spark. Now I'm building a medium power SSTC for almost free (sampled FETs, sec. wire from old big relay, other components from old SMPS's...)
I just checked and the only local electronic store which has the tube , has it for ~$30. Then you have to buy the resonant caps, which are at least as expensive.
Registered Member #543
Joined: Tue Feb 20 2007, 04:26PM
Location: UK
Posts: 4992
aonomus wrote ...
Well there have been alot of threads recently about VTTC's, I dunno, some odd nostalgia virus going around.
Surely, one of the great strengths of 4HV is the willingness of its members to take the technology of any period and press it into service, whether it be the Leyden Jars of 18th century Holland, or Victorian rotary spark gaps - compared with which thermionic valves are positively modern! Indeed, valves are still very much in use in very high power applications where they remain unequaled.
But all this is a bit beside the point - there is often among coil builders a strong artistic impulse (one need only think of TDU's endless creativity) and large, glowing vacuum valves have an appeal to the eye and senses completely missing from tiny silicon rectangles, however superior these may be from an engineering perspective.
Finally, how often do you read of TC applications in these pages? Almost never. The machines are created for the sake of the things themselves. They are electronic works of art.
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How does a VTTC work?
(sampled FETs, sec. wire from old big relay, other components from old SMPS's...)