Re: secondaries

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: "by way of Terry Fritz <twftesla-at-qwest-dot-net>" <FutureT-at-aol-dot-com>

In a message dated 10/8/01 7:16:16 PM Eastern Daylight Time, tesla-at-pupman-dot-com 
writes:

David,

Thanks for your nice comments about my coil work.
I agree it's good to have a high inductance to help reduce gap
losses.  I've calculated the inductance of your 12" x 38.5" 
secondary with 660 turns of 16awg wire at about 35mH, with
about 18pF of Cself.  My proposed secondary 10" x 65" wound 
with 1500 turns of 18awg wire has about 80mH, or more than
twice as much inductance, but just slightly more Cself at 23pF.  
Using a 65" tall secondary, much, much longer sparks can be 
obtained due to the greater voltage capability, and reduced 
likelihood of the sparks striking the primary.  Using a 65" tall 
secondary, it should be possible to obtain 22 foot sparks.

I still can't see why large coils would benefit from a different
aspect ratio than smaller coils, and I kind of doubt that they do.
It would be interesting to see a comparison test.  Of course a
short coil is good if you have limited available space.

John 
--
>  <IMO a 10" secondary 
>  <should be about 60" tall or so, maybe even taller.  The narrow 
>  <secondary has less self capacitance, and permits a larger toroid 
>  <to be used for a given input power.  A tall narrow coil tends to be 
>  <light weight, and can tolerate cheap, lightweight, thin wire.  The 
>  <sparks from a tall secondary are less likely to strike down and 
>  <hit the ground or the primary. 
>  
>  <My small coil, etc. is at: 
>  
>  <<<<http://hometown.aol-dot-com/futuret/page3.html >  
>  <John 
>