Re: tabletop coil first light

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Original poster: Jim Lux <jimlux@xxxxxxxxxxxxx>

At 10:54 AM 12/22/2004, you wrote:
> Original poster: hue jass <chesscactuar@xxxxxxxxx>
>
> Hello
>
> I got my new coil running today. the specs are as follows: 9/30 NST power 
> supply, 5 segment spark gapmade with copper couplings, ~7nF beer bottle 
> cap, 8 turn primary made with 1/4" copper tubing (tapped at about turn 
> 5.5), secondary coil form is 1.86" OD PVC pipe, 740 turns 28 AWG magnet 
> wire (~10" winding length), topload is a 2.5 inch sphere ( plan on getting 
> a bigger topload) first time i turned it on i got about 2" streamers. With 
> a little bit of tuning i got 3" streamers and 5" sparks to a flourescent 
> light bulb. I have 2 questions: 1. How much of an improvement could i 
> expect with an 8pF topload and 2. would electrical tape help control 
> corona around the edge of my beer bottles? Also, strikes to a flourescent 
> light bulb where bright blue and there was almost no heating of the 
> bottles, which leads me to believe that beer bottle caps aren't such a bad 
> option. Thanks for the help.
>
> Blake

Good going so far..

How long a spark can you get to a grounded rod? (this is a better measure 
than free air streamer length)

A better topload will help.  Toroidal ones have better field control than 
spheres. Think about getting some small pie pans (tart pans) and one of 
those foam "noodle" pool toys (or a 2-3" diameter foam insulation for 
pipes). Put two pie pans bottom to bottom (making what looks like a big 
pulley. Then wrap the foam around the groove, and then cover it with 
aluminum tape. You can also use a styrofoam "christmas wreath" form.

What's the bottom of the secondary connected to?  Do you have a decent 
ground plane under the coil?  A 3x3 or 4x4 foot piece of chicken wire can 
help a lot.

How long are the wires from beer bottle cap bucket to the primary? Where's 
the corona? At the tops of the bottles? at the water surface? A bit of oil 
(1/4" layer) on the water surface can help. Messy, but works.