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Registered Member #3026
Joined: Fri Jul 23 2010, 02:46PM
Location: Los Angeles, California, U.S.A.
Posts: 54
Gentlemen:
I am new to this hobby and have just completed the “recipe coil†in the Trinkaus book, “Tesla Coilâ€. My primary is six turns of Heavy, copper wire and my secondary is 437 feet of #28 magnet wire. My capacitors are sixteen beer bottles filled with salt water in a tub of salt water. However, my NST is only 6500 volts. I am getting a super good, loud, strong spark at the spark gap, but no streamers off my terminal capacitor. Instead, I get a lot of arcing from the primary to the secondary. Can anyone help me?
Registered Member #51
Joined: Thu Feb 09 2006, 04:17AM
Location:
Posts: 263
Your coil is over coupled and likely not tuned correctly. Try a flat primary or raise your secondary way up and out of your primary. After this is done, re tune your coil.
Registered Member #480
Joined: Thu Jul 06 2006, 07:08PM
Location: North America
Posts: 644
Radioman -
You have given us very little information. To troubleshoot this coil, please provide the following: 1. What is the calculated resonant frequency of your primary circuit? 2. What is the calculated resonant frequency of your secondary circuit? 3. What is the calculated primary-secondary coupling factor? 4. What is the total capacitance of your salt-water capacitor bank (either calculated or measured)? 5. What is the secondary current rating of your NST? 6. Describe the construction of your spark gap.
If you don't know the answers to questions #1-#3, download JAVATC from here: and input all your coil's physical dimensions and electrical parameters. You're best off if you can actually measure the capacitance of your capacitor bank, but you can also calculate the approximate value based on effective plate area of each bottle.
Run JAVATC, then post your results here for review.
Registered Member #480
Joined: Thu Jul 06 2006, 07:08PM
Location: North America
Posts: 644
arcstarter -
The intent of asking radioman all the specific questions about his coil is to help him understand what he's built, and help him understand why its not working. Yes, it appears that his current configuration is probably overcoupled, but if he takes the effort to determine what his current K factor actually is, then he can compare it against the typical range of K factors for spark-gap coils, understand why it needs to change, and what needs to be done to achieve a specific K value.
There's nothing inherently wrong with the design or construction of his topload, and there is no reason that a coil with a properly designed and constructed salt-water capacitor bank can't be made to generate moderate streamers.
The fact that you were only able to generate 2 inch streamers with your coil and its saltwater capacitor only means that there was a serious problem with your setup. Many coilers have achieved acceptable performance (2 foot or longer streamers) with saltwater capacitors. (See Mark Dunn's early experiments at: )
There's little doubt that a properly designed and constructed MMC using polypropylene film/foil pulse caps will give better performance than a saltwater capacitor with the same value, but saltwater caps CAN work acceptably well.
Let's give radioman a chance to post his coil's specs, and the Forum members can provide a comprehensive design review, looking at primary and secondary design, coupling, input power, primary-to-secondary spacing, topload-to-primary spacing, secondary turns count, toroid standoff distance above the secondary, salt-water capacitor design, spark-gap design, etc.
Registered Member #3026
Joined: Fri Jul 23 2010, 02:46PM
Location: Los Angeles, California, U.S.A.
Posts: 54
Thanks for your help, guys. The two coils were, indeed, overcoupled. I moved my secondary up about four inches and I am very happy with the results: Three to four inch discharge with by beer bottle caps! I have carefully tuned the coils with an oscilloscope and a signal generator.
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first coil wont work
