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Re: LC and Misc Questions

Original poster: FutureT@xxxxxxx

In a message dated 7/28/05 4:54:08 PM Eastern Daylight Time, tesla@xxxxxxxxxx writes:


    I have a couple of questions that have stumped me. There are too
many postings to look through regarding these questions and I was
unable find postings with definite conclusions or the info was way
too scattered.

   (1) I've read that secondaries should have LD ratios of 3:1, 4:1,
       4.5:1, etc. Which one is the best? Is there any critical
       difference?



The LD ratio should be reasonable.  There's not much difference
within some range.  Coils that are "fat" will tend to have more
inductance which is good but will be bulkier.


   (2) Enameled wire seems to be used exclusively. Why not stranded
       wire? It has better insulation and it is cheaper. It might
       also help reduce unwanted capacitance, which reduces voltage
       gain. For me, it actually worked better than magneet wire even
       though the sec. inductance is lower.



High inductance is usually desireable.  Larger coils can more easily
get away with using thicker wire and thicker insulation.  The stranded
wire tends to have higher RF losses.  I'm not sure if this matters
much on a secondary though.


   (3) I've read various opinions about how large primary cap and
       inductance should be. What is the paradigm in determining
       the best values?



I like to have a large primary capacitor so the coil can be run
at a low breakrate which is generally more efficient at producing
long sparks.  Higher break rates may give brighter sparks.  So
much depends on your goals for the coil.   Large inductances
helps to keep the tank impedance high which tends to reduce
spark gap losses.


   (4) One program, TESLAN, calculates voltage gain using primary
       and secondary capacitances. Another program, TESLAC, calculates
       voltage gain usiing primary and secondary L's. Which one is a
       better predictor of voltage gain?

   (5) Are there adv./disadv. of using stacked primares or multiple primaries
       wired in parallel?



stacked primaries take up less space.

    http:hometown.aol.com/futuret/page3.html

John