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Old 04-17-2012, 04:22 AM
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dR-Green dR-Green is offline
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Join Date: Apr 2008
Location: Wales, UK
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Originally Posted by jake View Post
I am having extream difficulty tuning one and I don't even know if I am doing that right. but I think I am getting a feel for it. Its hard to tell how much of the tuning should be done with distributed elements alone. As I noted in my last post adding a capacitor no matter how tiny seems to reduce performance. Putting my hand ~1" from the soda can peaks performance. Touching the can kills it.
Use a metal plate connected to earth/bottom of the secondary with adjustable distance from the can, and position it for peak performance. It won't like a variable cap very much across the secondary (unless maybe it actually goes down to zero pF), the type with rotating plates. I think vacuum variable caps might be usable here but they are expensive, so a metal plate near the can should do the trick. You can also lower the frequency by using a bigger can/pieces of metal. I think it's the surface area that applies in this case. Try connecting progressively larger pieces of metal and see what happens.

Also the bulb that Eric has recommended since is 28v 1.12 watt. I think that will be quite a task. The most I've seen on the scope with my flat spiral coil is 210mV so there's no possibility of lighting the bulb with that. I expect I need much better grounding which will be done at some point, but there's no way of adjusting the windings either so that's about the most I'll be able to do with that coil for the moment. [edit] Although I'm not entirely sure if it will even be possible with a flat spiral at all

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Last edited by dR-Green; 04-17-2012 at 04:32 AM.
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