Re: Tesla Coil RF Transmitter

["Tesla list" <tesla@xxxxxxxxxx>]

Original poster: "Malcolm Watts" <m.j.watts@xxxxxxxxxxxx>

On 27 Sep 2005, at 21:51, Tesla list wrote:

> Original poster: "Gerry  Reynolds" <gerryreynolds@xxxxxxxxxxxxx>
>
> To all,
>
> Is it not true that RC networks can only have poles on the real
> axis.  How do you get imaginary pole/zeros???
>
> Gerry R.

Agreed (first sentence). You don't (second sentence). But you can
certainly produce a bandpass/bandstop function without the use of
feedback and it does *look* like a resonant circuit if (a) you
consider just the frequency response and (b) realise that energy is
being dissipated rather than stored.

Malcolm



> >Original poster: "Malcolm Watts" <m.j.watts@xxxxxxxxxxxx>
> >
> >Hi Ed,
> >
> >On 27 Sep 2005, at 13:37, Tesla list wrote:
> >
> > > Original poster: Jim Lux <jimlux@xxxxxxxxxxxxx>
> > >
> > > At 11:17 PM 9/26/2005, you wrote:
> > > >Original poster: Ed Phillips <evp@xxxxxxxxxxx>
> > > >
> > > >"Excellent point, and a good example of a frequency selective
> > > >system that's band limited. Hmm, though, can one create an
> > > >arbitrarily sharp cutoff with only RC?  I think not, off the top
> > > >of my head."
> > > >
> > > >         We used to have a guy at Hughes named Lou Weinberg who
> > > >         had the
> > > >reputation of being a real expert on network synthesis.  I heard
> > > >him say that, using only PASSIVE RC circuits, it was possible to
> > > >synthesize any transfer function shape if the loss were allowed
> > > >to be arbitrarily large.  Don't know if it's true or not.
> > > >Certainly with a little feedback you can get arbitrarily sharp
> > > >response.
> > > >
> > > >Ed
> > >
> > > I've thought a bit (and am too lazy to go find my copy of Mason
> > > and Zimmerman, which I'm sure would have the answer)..
> > >
> > > I think you're right.  I was having trouble figuring out how to
> > > get sharp nulls (or more properly, sharp cutoffs).  A series of RC
> > > networks can get you more than 180 degrees of phase shift, and if
> > > you sum the 180 and the 0 path appropriately, you get a null. One
> > > can always string up multiple nulls (at different frequencies) to
> > > get what you need.
> > >
> > > I don't know that you can get the classic resonance curve, though
> > > (except with a huge number of sections).
> >
> >Twin T and Weinbridge networks spring to mind in connection with both
> >of those and I'm sure that's not the end of the story. I predict that
> >someone attempting to disprove the hypothesis about generating
> >transfer functions using only RC components (losses taken into
> >account) would have a very hard time.
> >
> >Malcolm
> >
> >
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