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Re: transformerless TCs/ would a variometer be useful?



Original poster: "marc metlicka by way of Terry Fritz <twftesla-at-qwest-dot-net>" <mystuffs-at-orwell-dot-net>



Tesla list wrote:
> 
> Original poster: "Antonio Carlos M. de Queiroz by way of Terry Fritz
<twftesla-at-qwest-dot-net>" <acmq-at-compuland-dot-com.br>
> 
> Tesla list wrote:
> 
> > Original poster: "Jolyon Vater Cox by way of Terry Fritz
> <twftesla-at-qwest-dot-net>" <jolyon-at-vatercox.freeserve.co.uk>
> 
> > With regard to transformerless/ capacitive transformer Tesla coils, I
cannot
> > help but think that where C1 is to be substituted for larger/smaller
> > capacitance it would be useful for L1 to be variable to facilitate
> re-tuning in
> > a similar to adjusting the primary tapping point on a conventional TC.
> 
> Certainly, and it would be better if L1 could be adjusted while the coil
> is working.
> 
> > Does this not sound similar to adjusting the impedance match of an
> antenna to a
> > radio transmitter using an Antenna Matching Unit- except that with an
AMU the
> > coils are largely fixed and fine tuning is done by a variable capacitor
> whereas
> > with a Tesla coil the reverse is usually the case.
> 
> Ok, due to the lower operating frequency, the capacitors are too big to
> be tuned (except for the terminal capacitance, where a telescopic
> antenna
> works very well).
> 
> > In view of this and the fineness of tuning (does tuning on have to be this
> > fine?) would not the variometer-type of variable inductor be the best
design
> > for L1 in a transformerless TC?
> 
> Yes. And for use as "off-axis" inductance in series with the primary of
> a
> Tesla transformer too.
> The tuning becomes fine in the low-coupling modes, that correspond to
> higher voltage gain in a directly coupled system, but it's not so
> critical.
> 
> > If the above is correct, does anyone have a design for a cheap, reliable
> > variometer, all the better if it were a small one- given the "miniature"
> nature
> > of my anticipated design
> > -L2 is only 5 5/16" tall and 1 1/8" in diameter and the final TC will
> > (hopefully!) be driven by no more than a flyback transformer.
> 
> Maybe two coils, one fixed and other that can be rotated, interconnected
> in series (or in parallel) by flexible wires. In the simplest design
> just

 This sounds very much like the antenna tuner that is inside an "old"
arc-5 military unit i got off of ebay. It uses a coil wound around a
ceramic tube (1.5" dia.) and then another coil inside the tube, this is
a flat coil that is rotated 360 degrees within the tube. It's been
awhile since i've really looked at it, but i could send a pic or send a
couple to hot-streamer if anyone is interested? I always thought that
this would be a great primary tuner if scaled too the needs of any coil?
Take care.
Marc M.


> make two coils, place them over a thick insulating plate (as I did in my
> setup), and move one of them to tune.
> 
> Antonio Carlos M. de Queiroz