RE: Tesla Coil Blunders

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: "Terry Fritz" <twftesla-at-uswest-dot-net>

Hi John,

That small coil has a resonant frequency of 351kHz.  When I put it directly
over a foil ground plane, that drops a bit to around 346kHz.  In Paul's
experiment, the top of the coil had a Tek5100 scope probe attached (3pF
load) plus a 1/4 watt 220k ohm resistor.  That is sort of like a streamer
load.  That 3pF plus 220k ohm top load drops the resonant frequency to
311kHz.  One could note that the 10% drop is rather high for a streamer
loads affect on Fo but I am running in a CW mode (or slow frequency sweep)
so the effect is a bit more pronounced than on a real disruptive coil.
Here are some sweeps of the probe and no probe situation:

http://hot-streamer-dot-com/temp/SmallCoilSetUp.jpg
http://hot-streamer-dot-com/temp/3-4noProbe.jpg
http://hot-streamer-dot-com/temp/3-4yesProbe.jpg

Here is also a picture showing clearly the double frequency effect that was
mentioned in another post.

http://hot-streamer-dot-com/temp/675tLoad.gif
http://hot-streamer-dot-com/temp/Tek00000.gif

These pictures are made with a storage digital scope and a synthesized
sweep signal generator.

http://hot-streamer-dot-com/temp/P2010014.jpg

Cheers,

	Terry



At 06:52 PM 3/29/2001 -0800, you wrote:
>
>Terry -
>
>On Paul Nicholson's web page your coil is listed with a 310.9 Khz resonant
>frequency. The Wheeler/Medhurst equations show this coil with a 345.86
>resonant frequency. This is a reduction of
>    (345.86 - 310.9)/345.86 = 10.1%
>In the frequency equation the R = 43,393 ohms.
>Did you find the 310.9 Khz with a scope and antenna probe when the coil was
>operating?
>
>John Couture
>
>---------------------------
>
>
>-----Original Message-----
>From: Tesla list [mailto:tesla-at-pupman-dot-com]
>Sent: Thursday, March 29, 2001 6:58 AM
>To: tesla-at-pupman-dot-com
>Subject: Re: Tesla Coil Blunders
>
>
>Original poster: "Terry Fritz" <twftesla-at-uswest-dot-net>
>
>Hi,
>
>In general, I have found the streamers load a TC to about 220K ohms plus
>1pF/foot of arc length.  This lowers the secondary frequency about 5 to 7%.
> MicroSim modeling also demonstrates this effect of streamer loading.
>
>Cheers,
>
>	Terry
>
>
>At 06:33 AM 3/29/2001 -0800, you wrote:
>>more likely the detuning is due to the loading of the
>sparks/corona/leaders.
>>Signficant C (pf/cm) and significant R (tens to hundreds of K)
>
>-------------------  snip
>