Re: Secondary Resonance LC and Harmonics.

["Tesla list" <tesla@xxxxxxxxxx>]

Original poster: Terry Fritz <teslalist@xxxxxxxxxxxxxxxxxxxxxxx>

Hi Chris,

At 11:34 AM 6/25/2005, you wrote:
> Hi All,
>
> I've just wound my first secondary, and in my eagerness I ignored most 
> guidance and just wound as many turns as possible on a piece of 3.5' x 4" 
> tubing.  It turned out to be approximately 2K turns (gulp).

Probably ok ;-)

> I managed to get my hands on a nice stainless steel sphere, which sits 
> nicely on top.  I was just 'playing' with my scope and signal generator, 
> when I discovered that when I set the sig gen to oscillate at 76KHz or 
> 416KHz I don't need to connect it to the coil in order to show the signal 
> on my scope, I only need to touch the probe and the signal magically gets 
> on to the coil and scope!

Yes, this is how folks with test equipment can check the resonant 
frequency.  Us about a 2 foot piece of wire.  The "official" antenna is 
described here:

http://hot-streamer.com/TeslaCoils/MyPapers/planant/waveant3.html

It provides a flat frequency response, but just a piece of wire works good 
in many cases.

>   - I'm guessing that my coil and top sphere are acting as a tuned LC 
> tank circuit, with a resonant frequency of 76KHz and a harmonic of 
> 416KHz.  Either side of these frequencies the signal drops off.

Yes!  The one that gives the strongest signal (also lowest frequency) is 
the main or fundamental.  There are higher harmonics too.

Paul has an extensive site on this:

http://www.abelian.demon.co.uk/tssp/

> Does this make sense?  Has anyone else experienced something like 
> this?  How *badly* tuned is my coil?  Should I take some turns off it (not 
> yet varnished)?

It depends on if you can tune the primary circuit to match that 
frequency.  It seems pretty low...  Might want to check with one of the 
many Tesla programs out there to be sure.  If your primary system will not 
tune to the same frequency, it is "bad"...

Cheers,

        Terry


> Thanks
>
> Chris