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MATERIALS


  > From: lisanap-at-cats.ucsc.edu (Mark Napier)
  > Subject: Materials

 MN> Hi Richard.  I am having a hard time finding 60 mil poly-    
 MN> ethylene in the  desired dimensions.  Around here all I can  
 MN> find are 4'x 8' sheets or rolls of 100 lbs. which cost $150  
 MN> or more.  No one that has rolls will sell me roll off        
 MN> footage.  Any source suggestions?

If the material being sold in the 4'x 8' sheets is LOW DENSITY
(soft, flexible) polyethylene, and careful examination of the
material shows it to be free of scratches, cuts, gouges, imbeded
particles, etc., then this material size will work just fine.

My sources would only supply the full rolls. 

 MN> What kind of clamp are you using on your primary connection?

Good question. I am using two copper fuse clamps mounted onto a
small brass plate. The brass plate was drilled, then tapped for a
1/4"x20 brass screw on one side for the connection to the tap
lead. The other side was drilled, tapped, and threaded for some
"junk box" copper screws which are used to hold the two fuse
clamps in place. These copper "spring-type" fuse clamps make
excellent tap connectors. 

 MN> I got a roll of 22 gauge today, so I will be winding away    
 MN> pretty soon. If I go 4.5:1 that will be 4"x 18".  One of the 
 MN> calculators gives me 667 turns for 595 KHZ.  With .02uf and  
 MN> 3/8 tubing with 3/8 spacing, it should tune somewhere        
 MN> between the 5th and 6th turn.  The toriod should be big      
 MN> enough to get the freq. down to about 421 KHZ for that
 MN> to happen. How big should the toriod be?  The power supply   
 MN> will be 12KV at 120ma. I've read the notes thru Apr-94.      
 MN> Maybe I just haven't got to that part yet. 
 MN> Thanks, Mark R, Napier <lisanap-at-cats.ucsc.edu>

I don't think I have given any specific toriod sizes for this.
Stretch this coil just a bit longer, get a few more turns on it.
Make up for the large aspect ratio by using a big, snugly coupled
primary. I would say go with a 20 - 24 inch secondary winding
length, those extra turns (750-880) will bring the frequency
down. Then add a toriod, bringing the frequency down even
further. A 15"x4" toriod would be good to get you started. You
will probably want two: an 15 inch diameter toriod, and a second
20 - 25 inch diameter toriod.

You want the primary to tap at around 8 - 9 turns minimum. Five
to seven turns just aren't enough for those peak efficienies.
Somewhere between 12 and 15 turns out on the primary is where
things are really happening: if you are tapping out this far, and
you are using an inverse conical section for the primary coil
form, you will have plenty of coupling on this 4" diameter coil,
even with an aspect ratio of 5, or higher.

Richard Quick




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