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Re: Discharge impedance of a CW Tesla coil

Hi John,

At 08:44 AM 03/10/2000 -0500, you wrote:
>In a message dated 3/10/00 6:41:05 AM Eastern Standard Time, tesla-at-pupman-dot-com 
snip..
>
>I wouldn't be surprised if the lower resistance seen in the CW coil is due
>to the longer time period during which the sparks exist, which produces
>more intense ionization over a smaller but "fuller" space.  Effectively
>it's sort of like a disruptive TC which gives many streamers, but even
>more intense because the sparks are there for a longer percentage of
>time.  I suspect that disruptive TC's having multiple streamers will show
>a lower than normal impedance also (but not as low as the CW coils).
>It will be interesting to see if this impedance changes if the coil is pulsed.
>Short pulses (short "on-times") may be needed to appreciably increase
>the streamer Z.  If we can increase the Z by pulsing the coil properly,
>we may lengthen the sparks.

Neat idea.  The generator does have a rear panel electrical connector for
remote control of it's functions and I know it can be pulsed (I will have
to find the specs on how fast but it is probably well into the kHz).  I
don't have a duty cycle oscillator but a 555 timer with a handful of parts
should provide the control signal easily enough.  I suppose it could play
music and such off the discharge :-)

> 
>>  I noticed that this coil produces almost no ozone or other noxious fumes in
>>  operation.  I was very surprised by this!  Perhaps all CW coils are ozone
>>  free and I just missed that bit of info.  Not gassing out the basement
>>  during this testing is VERY pleasant as is the quiet discharge!!  It is
>>  very cool but does not strike the "fear" those big disruptive coil
>>  streamers, gaps, and all do...
>
>I generally get quite a lot of ozone from my tube coils but I've never really
>done a proper comparison with the disruptive TC's.  The power levels
>probably have a lot to do with it.  In a small room, running a tube coil
>can be brutal.

Really!!!  I wonder why this one is so free of ozone and those nitrous
compound things???  I will look into this more.


>
>Good, let's get those old myths cleared away  :)
>>  
>>  I was very surprised that at
>>  300 watts I was able to tune the coil with ZERO watts reflected (the
>>  generator has a 50 ohm output through about 10 feet of RG-8).  My primitive
>>  computer models suggested such things but I didn't believe them...
>>  Apparently, primary inductance is not at all critical but coupling is...
>>  Of course, the RF generator is much more predictable than tubes (at least
>>  for me)...
>
>A typical tube coil runs half wave rectified, so the various matching
>aspects might not be as good?  I'll be interested to hear which coupling
>k value you find to be the best.

I use k=0.15 now because that just how it turned out and the computer said
it would be ok.  Now that I know the discharge impedance, the computer can
crank for optimal values.  Fortunately K is very easy to adjust.

Cheers,

	Terry