RE: New guy questions (fwd)

["Tesla list" <tesla@xxxxxxxxxx>]

---------- Forwarded message ----------
Date: Thu, 19 Jul 2007 08:46:58 -0400
From: "Lau, Gary" <Gary.Lau@xxxxxx>
To: Tesla list <tesla@xxxxxxxxxx>
Subject: RE: New guy questions (fwd)

Hi Dan:

Comments interspersed:

> From: Dan/Elaine G. <degargel@xxxxxxxxxxx>
> To: tesla@xxxxxxxxxx
> Subject: New guy questions
> 
> Hi all,
> 
> I wanted to introduce myself by way of asking a few questions.
> I started getting interested a few months ago, doing some research,
starting
> a design, scoring some hardware, and joining the List. Thought I stop
> lurking and ask-away.
> 
> I have also been following the recent FAQ thread btw, and I can
understand
> the difficulty such an undertaking might offer, since some of my
questions
> focus on some well intentioned yet mildly contradictory input I
collected
> from browsing various sites.
> 
> 1) How critical is the Secondary HD ratio?  I found some guidance, but
I
> also see some folks seem to ditch the convention - for example,
maintaining
> an HD of 4 to 4.5 for a 4" coil form. (I haven't run any what-if
analysis
> since I've been waiting for the math refresher to hopefully sink into
my
> brain).

The HD ratio is not overly critical, certainly not in the sense that
there is a discernable sweet-spot like choosing the optimum primary tap.
The ratios typically used just keep the length long enough to prevent
arc-over's and inductance sufficiently high.  

> 2) If I can afford an acrylic/plexiglas over a PVC Sec form, is it
worth it?
> (considering dielectric, looks, ease of using an adhesive, etc)

Bear in mind that the secondary coil form is not at all used as a
dielectric.  Of course it is subject to a high frequency electric field,
but not at as intensely as in an actual capacitor.  So while PVC is not
a suitable tank capacitor dielectric, it's just fine for a secondary
coil form.  And it's worth noting that acrylic is also deemed to be
unsuitable for a tank capacitor dielectric, but equally fine for a coil
form.

> 3) Best place to score some Cornell Dubilier caps for an mmc: does the
Geek
> Group really sell them? to non-members? Should I try eBay or another
source?

I don't think the Geek Group still sells them.  I have not personally
bought any, but others have suggested Richardson Electronics, phone
number 1-888-735-7358.
0.15 uF 2000 VDC Cornell Dubilier caps, Part Number 942C20P15K-F

> 4) One curiosity question, in my past acquaintance with circularly
polarized
> antennae, I was just wondering if there was a winding-sense convention
(left
> or right-handed) that applied to coils as well. I've found no such
advice
> (probably for an obvious reason). Does it help or not matter at all?

It doesn't matter.

> Too many questions? Reply here or to my address - whatever is better,
> 
> Thanks tons,
> Dan in PA
> 
> I got a variac(!) and a 15/30 NST.

Regards, Gary Lau