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RE: [TCML] poor coil performance again- help!



Thanks, I think I will just design a new one. By the way, are there
specific rules about ratio of L and C in the primary and the secondary?
In other words, for both resonant cicuits, what should be the relative
contribution of L and C to resonance? And what resonance frequency
should I aim for? As low as possible?

Many thanks

Thomas

-----Original Message-----
From: tesla-bounces@xxxxxxxxxx [mailto:tesla-bounces@xxxxxxxxxx] On
Behalf Of bartb
Sent: 22 April 2008 05:08
To: Tesla Coil Mailing List
Subject: Re: [TCML] poor coil performance again- help!

>   Sorry I sound so depressing, but the more I looked at it, the more 
> trouble I realized. I've been down your road with a small coil a while

> back. It sucked! I had a couple hundred more turns than yours, but the

> coil was even smaller. Primary was fixed at 4 turns and I tried it 
> with a 7.5kV 20mA NST. I eventually installed a 12/30 to force some 
> power into the coil, but it was still dismal. I ended up giving it to 
> a buddy. He thought if he wound another layer of turns on the 
> secondary he could get it working better. Too bad he didn't ask me 
> first. Oh well.
>
> If you want a good performing coil, then you need to design with the 
> following in mind:
> 1) 900 to 1300 turns.
> 2) H/D ratio between 4 and 5.
> 3) A coil diameter of 4" or larger.
> 3) Good static gap with lots of air cooling or srsg.
> 4) A transformer about 12kV or near with at least 60mA.
> 5) An MMC cap designed for LTR operation (it's value) for the static 
> gap or srsg (and those values are different).
> 6) A primary that tunes between 10 and 15 turns.
> 7) A toroid sized appropriately for breakout, loading size, and as 
> smooth as you can get it.
>
> The above are just some very basic preferences. Your coil hits #2 and 
> slightly #3.
>
> I'm sure if you worked with the coil, that you can get it performing 
> better, but there is a limit with the coil and that's what I'm trying 
> to get across. I guess if it were me trying to get the coil working 
> better, I would ditch the bottle caps and build an MMC with a larger 
> cap size. But this would require a larger turn primary, so I would 
> have to build that also. I would also upgrade the NST and install a 
> toroid top load which will help lower the frequency (which helps in 
> other areas).
>
> It of course takes work, time, and money to make a decent coil. It's 
> not rocket science but there are pit falls to watch out for and 
> experience is the best teacher.
>
> Take care,
> Bart
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