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Re: 3000 turn secondary



Hi Marc, 

Tesla list wrote: 
>
> Original poster: "Metlicka Marc" <mystuffs-at-orwell-dot-net> 
>
> thanks john, malcolm, all 
> the reason i was asking is that i bought a 8" sona tube for a new 
> secondary, i already have 7# of #28 mag wire. when i got the tube sealed 
> up and ready i ran the numbers through wintesla, wow at 40" long i am 
> looking at 3006 turns. i figured if there was some great loses involved 
> in that many turns i would have to get different wire? 
> the way it looks is that if i use 1/8" copper tubing spaced at .3" i'll 
> have 27 turns to 150' 
> of tube, with an inductance of .3936mh. primary cap to res. is .0387uf, 
> my new cap is .052uf so it shows the tune at 23.7 turns and an 
> inductance of .2942mh. 
> with a topload of 32.53pf and 21kv-at-85ma as a psu, res. freq. -at- 40.80khz. 
>
> if no one sees any major fault with this setup i might just try it? i 
> was saving the wire for a 12" form but if this works maybe i'll make 
> another just like it in the future for a duel coil set up? 
> i would like to get another sec. built for the ne. ohio teslathon as my 
> secondary now is like a homely woman, faithful and dependable but ugly. 
> any suggestions will be appreciated and valued. 
> marc




The design sounds fine. It looks like you'll need about 3 lbs. of wire, so a
twin coil is very probable out of the same spool. I took a look at what would
occur if you space wound the coil with a spacing of half the wire diameter
(.0063"). It would then require 2000 turns. Your frequency would increase to
around 59kHz loaded. You have a couple things going on if you do this. You
increase the skin depth losses, but you decrease the turn to turn proximity
losses. I'm not sure which one would be best over the other. Another occuring
feature is you'll go down to about 16 turns on the primary increasing gap
losses. I'm not sure if the changes are small enough to really make much of a
difference between the two. As much as I would love to see you space-wind the
coil, it's ultimately your choice to do what you think is best. Of course, one
way to tell is to wind two coils (one close wound, one space wound, and make
the comparison). The space-wound coil would take about 2 lbs. of wire, so maybe
enough left over for a third coil! 

Just throwing a couple pennies your way. 
Bart