30MHz Spark Gap Testing - Is this real??
From: D.C. Cox [SMTP:DR.RESONANCE-at-next-wave-dot-net]
Sent: Tuesday, April 07, 1998 12:09 PM
To: Tesla List
Subject: Re: 30MHz Spark Gap Testing - Is this real??
Your work is very clever and quite timely. I would urge you to consider
forwarding a copy to Harry Goldman for publication in a future edition of
TCBA News. We have always used a xmfr / SG parallel configuration with the
cap in series downstream. This seems to provide optimum life for NST and
potential xmfrs when operated as a power source for Tesla oscillators. If
you test setup is still active you might repeat your experiments adding the
secondary coil and setting its discharge path to a short 3-4 inches. It
would be interesting to see what effect this extra "load" has on the data.
Please keep us on the list posted.
> From: Tesla List <tesla-at-pupman-dot-com>
> To: 'Tesla List' <tesla-at-pupman-dot-com>
> Subject: 30MHz Spark Gap Testing - Is this real??
> Date: Monday, April 06, 1998 8:02 AM
> From: terryf-at-verinet-dot-com [SMTP:terryf-at-verinet-dot-com]
> Sent: Sunday, April 05, 1998 11:44 PM
> To: Tesla List
> Subject: 30MHz Spark Gap Testing - Is this real??
> Hi All,
> I believe that I have made a new and significant discovery regarding
> gap operation. My experiments, which deal with the measurements of
> and currents in the primary circuit, have shown that the operation of the
> spark gap is not that of a simple switch.
> It is generally believed that when the voltage across the spark gap
> a certain level that current passes through the gap and super heats the
> creating a virtual short across the gap. This short remains in place
> the primary circuit losses energy and the super heated air region can no
> longer be maintained. At this point, the resistance is believed to rise
> the gap "quenches" and the resistance returns to a very high level.
> measurements performed with relatively low bandwidth equipment more or
> have demonstrated this phenomena. Once the gap has closed, the current
> through the gap is assumed to be a simple decaying sine wave.
> When equipment capable of much higher bandwidth is employed this picture
> seems to change dramatically. When one terminates a quality antenna into
> the proper 50 ohm impedance the fundamental signal seems overwhelmed by
> heavy noise spikes. This explains why a simple wire is often used as a
> scope probe to receive primary waveforms as opposed to a higher quality
> antenna system. The simple wire and its very poor impedance matching to
> input of an oscilloscope attenuate these noise signals so that only a
> clean signal is left.
> If one uses a high bandwidth properly terminated antenna, a series of
> spikes are seen (my testing was done without the secondary inductor in
> place). Careful examination will show these spikes appear as a series of
> noise bursts that occur at the peaks of the fundamental frequency. The
> power of these noise bursts is vastly higher than the fundamental
> In my testing, I have found that these burst consist of ~50MHz signal
> that persist for about 100nS and then fall off to a much lower level.
> power of these bursts is remarkable. Early testing has shown that, even
> low voltage levels, these bursts may reach many hundreds of amps at the
> ~50MHz frequency. By far the most powerful burst is the very first one.
> Typical scope photos often show this as a vertical line that occurs just
> the beginning of conduction. My equipment has not been able to measure
> level of this spike with great accuracy but it appears to be around 400
> which is remarkable considering the relatively low 2000 volt spark gap
> setting. What is even more remarkable is that the current outside this
> burst appears to be close to zero. In other words the full current in
> primary seems to be conducted only in these short bursts.
> Others and I have measured nice sine wave currents in the primary system
> before. So how can the preceding be true? I fear we have been tricked
> the low frequency response of the equipment we used and the classical
> impulse response of those systems. These energy bursts can easily act as
> pure impulses which will excite a low bandwidth system producing sine
> We may have only been seeing the heavily damped response of these current
> What are the implications if this is true? If the primary circuit is
> all of its work at ~50MHz and at hundreds, if not thousands, of amps at
> frequency, everything changes! The conductors must be short, wide,
> strips. The capacitors must be able to withstand even greater stresses
> we ever imagined. And the spark gaps... who knows? This would imply
> much better spark gap or other switching system may give much better
> performance. EMI becomes a major concern. At 200KHz it is easy to
> disregard EMI. At 50MHz all kinds of problems can arise.
> I have written a paper on all this. It is available in Word 97 format
> as an HTML web document at:
> Look at the 30MHz Primary Circuit Measurements section. You may want to
> save the graphics and view them with a viewer to get the highest
> The main page is:
> I realize this is a rather dramatic change in the way we all look at
> primary circuits. I have tried my best to confirm this. Unfortunately,
> seem to be rather alone in my ability to probe into these regions so
> independent confirmation is difficult. However, I am confident that the
> truth will be determined quickly. As far as I can tell everything
> to be working properly and all the results I have seen make sense and
> very real.
> Comments are very welcome.