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Re: Parallel and Series LCR Circuit Qs
and, as I think about it.. what sort of load would you put at the far end of
the transmission line?
A short? An open? A resistive termination (representing the thermal heating
of the air at the end of the leader)..
There is some discussion in the literature of what happens when a leader and
spark channel grows, then shrinks back (say, driven from a bipolar pulse
Probably a resistive termination. You wouldn't want a reflection back down
the line,even though, because the line has a significant resistive component
(representing the heating of the air along the spark channel), the
reflection would be rapidly attenuated.
From: Tesla list <tesla-at-pupman-dot-com>
To: tesla-at-pupman-dot-com <tesla-at-pupman-dot-com>
Date: Thursday, August 10, 2000 12:20 PM
Subject: Re: Parallel and Series LCR Circuit Qs
>Original poster: "Jim Lux" <jimlux-at-jpl.nasa.gov>
>Hmmm.. what about modelling the spark as a transmission line. Scaled to a
>length so that the propagation takes the right amount of time. Just as in
>transmission line with an impulse, the source driving it doesn't "see"
>where the propagation has gotten to. So, it would appear to have a
>increasing C, as the step function propagates down the line....
>The series L per unit length would be 1 uH/meter (roughly) and the C per
>unit length is 5-6 pF/meter (roughly), so the characteristic impedance
>be sqrt(L/C) or 500 ohms...
>The propagation velocity of a spark is around 1E7 m/sec, so your
>transmission line would need to be scaled to 30 times the real length
>(3e8/1E7), for a scaled L of 10 nH/meter and scaled C of .05 pF/meter
>(keeping the impedance the same...). I'll bet you could work the
>series/parallel R in as well....
>you could even get fancy and hook up a bunch of transmission lines in a
>forked pattern, more representative of real sparks.
>This might start to have time domain properties that are realistic in a
>simple SPICE type model.
>From: Terry Fritz <twftesla-at-uswest-dot-net>
>To: jimlux-at-jpl.nasa.gov <jimlux-at-jpl.nasa.gov>
>Date: Wednesday, August 09, 2000 11:33 AM
>Subject: Re: Parallel and Series LCR Circuit Qs
>>At 06:24 AM 8/9/00 -0700, you wrote:
>>>> So the Tesla coil "source" basically needs to be impedance matched to
>>>> supply this "load", optimally.
>>>Of course, the impedance is time varying too, with the C growing as the
>>Yes! I assume the coil should be optimally matched when the streamer is
>>longest since that is were every bit of energy needs to be to push the
>>streamer that little bit further. If a coil is matched for a 10 foot
>>streamer, it will not mater if the matching is poor at 1 foot. It will
>>have no trouble getting past one foot and on to were every little bit
>>counts out at 10 feet or the edge of it's available power where fine
>>Of course that "may" not be theoretically the 'best' point considering the
>>other dynamics going on. But it is my best guess...