Re: Primary Winding

 * Original msg to: Gcerny-at-ix-dot-netcom-dot-com
 * Carbons sent to: usa-tesla-at-usa-dot-net

Quoting gcerny-at-ix-dot-netcom-dot-com (Glenn Cerny):

> I am a bit confused about what I am going to wind up with
> here. Maybe it will spark, maybe not.  My original 3.5 PVC
> has been shelved in favor of a 4" acrylic tube that I have
> acquired.  I have 22ga to wind it with.  Have the first of
> 2 static gaps built per coilbuild instructions (the ones in
> 6" drain pipe with 1.5" copper gaps with a muffin fan).
> Teslac shows with a wind length of 18" that the freq w/terminal
> is 420khz. With a .02 cap, a pri conductor dia of .375, 
> spacing of .5, inside dia of 7", o.d. of 14.75 and 5 turns.
> I figured that 30' of tube would be plenty.

> Could you tell me where I am going wrong please?

First, you never want to run a coil system for any length of time
with only five turns on the primary; coil systems start to get
efficient when the primary is tapped out over eight turns, and
peak out with between 12 and 15 turns tapped out on the primary. 

Second, teslac is not calculating the frequency drop that you get
when a discharge terminal is connected to the top of the second-
ary coil. The use of a large toroid is essential to high perform-
ance in this design. A toroid large enough to really get this
coil performing will drop the resonate frequency of the secondary
below 300khz. How many turns does Teslac say you will need to hit
this new lower frequency in the tank circuit with a .02 micro-
farad cap? That is not the end of it either, to really peak this
coil you will need an even larger toroid to depress your
secondary frequency below 250khz, what do you do then?

Then another consideration... Winding a good primary is not easy,
nor quick, nor cheap. It pays in the long run to build the most
versatile primary possible; which means a large primary with lots
of turns. You will find that larger primaries will allow you to
grow and fire larger diameter secondaries, but a five turn
primary will end up being nearly useless as you progress. My old
five turn primary, wound with 30 feet of 1/4 inch OD copper
tubing only worked with one coil (my first), and even then it did
not work very well. I kicked myself for not designing a higher
inductance primary coil, and ended up scrapping it for copper to
use in my RF ground. My second primary was better, fifty feet of
conductor. This worked with a couple of different small secondary
coils before I brazed on a 15 foot extension to further increase
the versatility. Having done this the hard way I can tell you
that I won't even consider designing a primary with less than 60
feet of conductor, and preferably 75 feet. This is for smaller
coils. On larger coil systems (six, eight, and ten inch diameter
secondaries) I go with 100 foot conductors.

I am not telling you what to do. I am just speaking the voice of
experience. A sixty foot long conductor is the minimum I
recommend for starters, and given a choice I would say go with 75
feet of primary conductor. You will find a need for the

Richard Quick

... If all else fails... Throw another megavolt across it!
___ Blue Wave/QWK v2.12