[TCML] VTTC Coupling
futuret at aol.com
futuret at aol.com
Tue Sep 16 15:08:30 MDT 2008
I don't think I've seen you post on this list previously?
But in any case I remember seeing your VTTC work
many years ago on Richard Hull's tapes. I remember
you used a metal chassis for your coil and at one point
you used (or were planning to use) five of the 811A tubes.
I remember you showed the bushy looking sparks that
were produced at a certain tune point.
From: Dan Elyea <fsiyfr at okeechobee.com>
To: tesla at pupman.com
Sent: Tue, 16 Sep 2008 2:49 pm
Subject: [TCML] VTTC Coupling
There is a really fun thing that can be done with an overcoupled VTTC.
can't take this to really high powers or you'll chance breakout from the
secondary below the top of the winding, but it's fascinating for the
experimentally inclined. Also, the necessary close physical spacing
tight coupling raises voltage breakdown issues between windings, and
limits how far you can push the system.
You have to deliberately overcouple the primary and secondary, and
the classic double-humped response. Get the coupling strongly into
mode with two very prominent humps. Then, with careful adjustment of
primary tuning, you can get the circuit oscillating on two frequencies
simultaneously. A scope is very helpful for this. However, the
(and sound) of the output discharge changes dramatically when you get
two frequencies going at once, so a scope isn't absolutely necessity.
discharge looks a lot more like multi-forked lightning rather than the
typical VTTC brush. With a scope, you can see the two frequencies in
waveform. As you bring up the HV, one frequency kicks in first, and you
have the typical "regular" VTTC discharge appearance and sound. Going
higher in voltage, the second frequency kicks in (and the first one
running, too). You can see it happen on the scope, and simultaneously
and hear it in the discharge.
Try it-you'll like it. It may not be as long of a discharge, but it is
more interesting, in my opinion. Running paralleled 811As and
MOTs, I got a loud, dramatic discharge. Very snappy sound in the
discharge. The main problem I ran into with this was breakdown between
primary and secondary. Eventually, I resorted to filling the space in
between them with RTV silicone sealant so I could run full power. (The
physical spacing between windings was a little less than an inch.)
Secondary was wound on a four-inch polystyrene form with #26 enameled
About 24 inches or a little more of winding, as I recall.
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