Re: Re. Resonance
Why not measure its resonance. Don't have the equipment -- no problem.
Just cart the sec inductor and toroid down to a small (emphasis on the word
SMALL) local TV repair shop. Describe your "very interesting project" to a
good service manager and ask him that if perhaps you left it with him for a
few days, and during a time period when work was slow, if they would be so
kind as to take a measurement for you. It only requires a RF signal
generator and a oscilloscope. Tell them to feed the sig generator ouput
into two turns of wire wrapped around the very base of the the coilform ---
just below the start of the secondary winding. Take a resonance reading of
the lowest freq large resonance you hit -- there will be a few other
resonances but the values will be low -- the lowest freq is usually the
largest and correct resonance. Take readings with toroid on and off the
This entire test will only take approx 5 minutes. If you use proper
diplomacy you will be amazed at the results you can achieve with regard to
Tesla coil work. A few students I know used this approach to obtain a few
FREE NST's for their project. Take along some photographs of another
working TC. Describe your project and hard working efforts to achieve it's
construction. Most techs enjoy their work and would love to help you out
-- if only you ask.
I have mentored experimenters (young HS students) who have even talked a
local surplus house into donating FREE the caps they needed for both their
oscillator tank circuit and their NST protection caps -- and resistors.
Then they talked a neon shop into donating a FREE xmfr for their project.
They were so poor they didn't even have a variac --- so they borrowed one
from a local technical college during the summer period when there was no
activity in the school. They even obtained their secondary coil wire from
a local company that winds solenoids for industrial applications.
Use your imagination and a "positive can do attitude" and you will suceed
in the TC project -- as well as in other endeavors in life itself.
> From: Tesla List <tesla-at-pupman-dot-com>
> To: tesla-at-pupman-dot-com
> Subject: Re. Resonance
> Date: Thursday, January 21, 1999 5:04 PM
> Original Poster: Gary Lau 21-Jan-1999 0804 <lau-at-hdecad.ENET.dec-dot-com>
> >Original Poster: Philip <shadow42-at-totcon-dot-com>
> >I have recently been trying to determine resonance of my coil. I dont
> >really know what value it has, but ive seen that quite a few people have
> >measured theirs. Does 243khz sound reasonable for a 4.5 x 20" coil?
> >Thanks Philip Mac Duffie
> You didn't say what you had for a top load. My secondary is similar:
> 4.25"D x 23.25"L (winding length) 22 AWG wound on 1/16" wall dried/sealed
> PVC drain pipe. Many layers polyurethane. Low voltage self-resonant
> with no topload at 489 KHz. With 4.5" x 15.5" toroid, Fr is 290 KHz.
> With additional 6.25" x 24" toroid, Fr is about 205KHz.
> Regards, Gary Lau
> Waltham, MA USA