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RE: DC TC 1/2

<On 2/16/97 Gary Weaver got all Charged Up and Wrote>:

T>Has anyone built a DC powered Tesla Coil other than a tube type Tesla
T>Coil?

T>A tube tesla coil is basically a pulsating DC Tesla Coil.

        No. No. And, No.  The tube =can= be powered by dc, in which
        case it puts out a "pure" rf wave - i.e. the rf output is
        is unmodulated.

        In Tesla work, the tube can be powered directly from ac
        without any rectification thereof.  In such case the rf
        output is amplitude-modulated at the 60-Hz. (in the USA)
        frequency of the ac line.

        The practical effects of this 60-Hz. modulation are
        these:

                1) -  You can (usually) hear the 60-Hz. hum
                      in the coil's output

                2) -  The 60-Hz. may interfere with certain
                      types of tests or measurements.

                3) -  The effect of amplitude modulation is
                      to generate sidebands which make the
                      voltage output of the coil much more
                      complex.  (This is a correlative of 2) )

T>A car ignition coil is DC and operates from points that open and
close. T>But it's not TC.

        You ain' gonna be doin' no work on my car, boy!  American
        cars since ca. 1970 have had solid-state ignition.  The coil
        is pulsed by a switching transistor.  These have no resem-
        blence to a TC.

        Ye olde tyme car - with mechanical points:  The points
        were usually bridged by a capacitor (called a "condenser"
        in those days, sonny).  Ergo, the coil's output had a
        certain rf component.  So it was somewhat TC-like.  To a
        degree.  Sort of.

T>I found an artical where someone built a large auto transformer that
T>produced 42" sparks from a battery power supply.  It's not TC either.

        Yeah - so ??

T>Many years ago I built a crude Tesla Coil using a DC power supply an 810
T>tube and a signal generator to drive the control grid.

        Yeah - so ??

T>It seem to me if a DC power source could be pulsed at resonate frequency
T>it would work fine for a Tesla Coil.

        I don't know about the pulsing of the dc power source, but
        you're starting to make my head throb:

        It doesn't matter a twit whether it pulses or not.  Or how
        either.  The primary of a TC requires oscillatory current
        whose frequency matches the natural resonance of the primary-
        secondary-terminus combination.   Period.

T>The next question is what is the best way to pulse a DC power supply
T>with out a tube?

        Most of us like to use a =spark gap=.  (Helluva a thing,
        they are too - helluva a thing).

[ ... ]


T>For a TC operating on an AC 12K transformer the peak to peak voltage
T>swing would be 19,968.volts.  For the DC power supply to be equal to the
T>AC example the DC supply would have to be 19,968. VDC.

        Now it's really throbbing:  The =peak= voltage is the
        rms voltage multiplied by the square-root of 2.

        Thus 12-KV rms = 16.968-KV =peak=

        =Peak-to-Peak= voltage of a symmetrical wave is twice the
        peak voltage.  In this case 16.968-KV x 2 = 33.936-KV.

        Only the =peak= voltage is of real importance in most TC work:
        It's the maximum voltage seen by the capacitors (resonance
        effects neglected).  It's  also the figure which determines
        how wide a gap the spark will initially jump (You know,
        spark-gaps, those pulsing devices).

        An exception occurs in a TC circuit where the capacitor
        is in series with the spark gaps =and= the gaps are so

(Continued to next message)