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    spark gap transmitter multiple series spark gaps

    Hello, I have seen in some old spark gap transmitters multiple spark electrodes in series, that create multiple series sparks. Why they are used in series instead of using just one spark?

    •   Alt1st June 2012, 09:05

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    Re: spark gap transmitter multiple series spark gaps

    To keep the spark in a straight line, so that the total breakdown voltage remains stable/constant.



    •   Alt1st June 2012, 09:51

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    Re: spark gap transmitter multiple series spark gaps

    Which type did you see ? the DC type

    or the AC Rotary Spark gap with RF tuned filter and RF AM modulated key


    I do not know for sure, but this is my opinion based on looking at these photos.

    In either design serial spark gaps make the design more reliable. So that the cleanest contacts at the same gap, would breakdown first, triggering a race to charge-up and dump the remaining shared high voltage charge.

    Either design could use this feature. If you imagine the effect of air capacitors in series each with a limited dielectric breakdown where they short circuit at the breakdown.

    initially even if perfectly equal gaps and capacitance they would split the high voltage equally until the weakest one arcs ( smallest gap). When the 1st dumps, it charges up remaining caps to share the total voltage , which are designed to arc immediately, and thus triggers a rapid successive chain of arcs iafter the 1st.

    The arcs being negative resistance characteristics like SCR's rapidly dumping their charge plates Ic=C*dvt/dt. with high voltage in microseconds..

    Over time spark gap electrodes tended to insulate them with carbon deposits and raise their dielectric breakdown so the gap with the lowest arc voltage always started the chain of breakdown. so having more spark gaps increased the reliability of constant least breakdown voltage. It also increased total capacity of charge Q = C1V+ C2V +...

    The most sensitive or cleanest electrodes and the lowest breakdown voltage, would start the chain reaction in the series string.

    These repeating rotary motor driven impulses could trigger harmonic resonances at a tuned AM band channel to radiate AM RF telegraphy modulated by a telegrapher's "shunted cap" on the low voltage section of the antenna stage.

    So in short ( pun by accident) "multiple spark electrodes in series" the electrodes could be in any physical orientation rotary or linear but always the series. The effects extended the life between maintenance functioning with trigger voltage with the pair with the cleanest contacts which distributed the againg effects while increasing the overal energy of the system with series connected capacitors in effect with almost equal breakdown voltage.

    So that is my rough reverse engineering analysis.

    Fortunately with spark plugs our cars use these days and cleaner burning fuels, we dont think about replacing our spark plugs anymore. I think we often forget they exist.

    Imagine the EMI and Xray emissions with Ozone smell around these machines and the sound effects of rapid fire serial arcs. It must have been magical, Brilliant and slightly dangerous. dah dit dah dah dah dah dah dit dah

    Brilliant.

    I thank you for reading this slightly enlarged explanation. I explains, how I see things hidden from a schematic. It is not brief or best way to teach or explain it.
    But I try to explain the reason why it functions this way and motivation from decades of design experience.

    Tony

    If you agree, vote, if not dont.
    Last edited by SunnySkyguy; 1st June 2012 at 13:07.
    Before you ask, Where is your Spec? What are you assuming? How did you verify? What did you try?

    "Ohm's Law and Uncertainty Principle" applies to life... Tony Stewart EE since 1975


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    •   Alt1st June 2012, 12:34

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    Re: spark gap transmitter multiple series spark gaps

    This looks like something called a Marx generator. There are references to it being used as a transmitter.



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