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Re: Newbie Question- what toroid size?
Original poster: Steve Conner <steve@xxxxxxxxxxxx>
What!! Are you saying that the resonant frequency is dependent only
on the wire length and the top load size has no effect???
Jared's Tesla coil design method consists of choosing a topload of
the right capacitance to make the resonant frequency equal to the
quarter wave resonance of the length of wire in your secondary. If
you do that, then that is indeed also the right frequency to tune the
primary circuit to.
However, most of us believe that there is absolutely nothing special
about the quarter wave resonance frequency. You can use more topload
than Jared's design method recommends, and if anything the
performance is improved. Provided of course your power supply and
capacitors can deliver enough energy to charge the bigger topload to
its breakout voltage. If not, the performance may be unchanged or
even get worse.
These days I like to choose the topload capacitance such as to make
the characteristic impedance: sqrt(L/C) equal to about 50,000 to
100,000 ohms. If Terry's "220k+1pf/foot" thing is correct, then this
gives the resonator a loaded "Q" of about 5 to 10, once you allow for
the series to shunt transformation. (Terry's model uses a series R-C
circuit, but the resistance that determines the Q is the equivalent
Matt: Alan Sharp and I have been running a mini Teslathon up here in
Scotland recently. We call it R.F. Burns Night ;-)