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Re: curious TC questions on Freq. limits



Original poster: "Jim Lux by way of Terry Fritz <twftesla-at-qwest-dot-net>" <jimlux-at-earthlink-dot-net>

A
> >>Hello, I have been curious about a few things with a tesla coil.
> >>First:  I have read some of tesla's patents and articles.  It seems
> >>Tesla talks of a TC running in the MHZ to 100MHZ ranges, has anyone done
> >>this?
>
>         One of the Professor Corum's grad (?) students
>         built something very like a Tesla Coil at 160
>         MHz, with a simple 1/4 wave vertical.  Operated CW
>         it had 'plasma flames' off the top end.
>
> >>  Is it possible?
>         sure.
>
>         Useful/practical may not be the same question.
>
>
> > There's a project paper around in which a group made a 5 MHz TC.

At risk of raising the 1/4 wave controversy once again, I (oddly, at the 
suggestion of Jim Corum) tried building a parallel open wire transmission 
line, about 20 ft long, shorted at one end, open at the other, transformer 
fed at the short with a matching network.  I fed it at frequencies from 20 
MHz on up with a few hundred watts, and lo and behold, one does get sparks 
and corona every quarter wavelength. Dr. Corum claimed that you could do 
the same with a coaxial transmission line made of concentric copper pipe 
and get a fairly steady state discharge at the open end of the coax. (I was 
looking for a way to ignite ring vortices with entrained particles)

However, I think this is a very different state of affairs from the average 
TC.  This is straightforward impedance transforming in a transmission line, 
and I think TCs are more of a lumped circuit thing. As the frequency goes 
up, the "nonlumped" behavior of components becomes more and more important, 
as anyone who has had to build (and make work) RF (or fast digital) 
circuitry above 30 MHz (or even lower) has found.