# Re: JF efficiency theory (again)

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

In a message dated 2/18/01 4:05:46 PM Eastern Standard Time, tesla-at-pupman-dot-com
writes:

> Original poster: "Mike Novak by way of Terry Fritz <twftesla-at-uswest-dot-net>" <
> acmnovak-at-msn-dot-com>
>
>
>  http://hometown.aol-dot-com/FutureT/page5.html
>
>  I was wondering why some coilers get such good results when completely
>  disregaurding such details. For instance, Ross Overstreet's coil:
>  6"x24" wound with #22 for a total of ~880 turns, a primary of approx 7-8
>  turns (from the photo) and ~2.2kVA input along with a static gap. He gets
>  6-7 ft sparks which is just about right from 1.7(sqrt(input power)).
>  However, he's only using half the reccommended number of turns on both the
>  primary AND secondary. Is it possible that it is not the NUMBER of turns,
>  that maybe it's simply proportionate on some level?

Mike, all,

First of all, the ideas I speak about will only gain about 10% more
spark length, so it's hard to tell the difference unless careful
comparisons are done.  Because of the differences in different
systems, I don't think any conclusions can be drawn without
making comparisons on the same coil, using different primaries
and secondaries.  (unless the coils in question were basically
exactly the same, etc.)  I do think the number of turns is
important, not just the proportion.  I suspect that as coils get
larger, they can do somewhat better than 1.7x sqrt..... etc.
>
>  Also, I Find that where people follow the 1600 turn rule they, more often
>  than not, neglect the 24-34 primary turn suggestion. I personally don't see
>  how one could always use 24-34 turns and still maintain a resonant
>  condition.

It's not really necessary to have 24 to 34 turns on a larger coil, or even
a smaller coil.  It is enough just to use more turns than usual on
the primary and 1600 turns on the secondary.  The primary turns will
have to just fall as it may, to tune the coil with the cap size needed.
But at least the surge Z will be as high as possible.

>  How is anyone supposed to achive such high levels of efficiency
>  if they must choose between resonance and high primary surge impedance?

See above.

>  Are
>  we just supposed to use thin wire on the primary?
>  I once used two #22 wires in parallel for the primary on an early coil I
>  made. It worked quite well too.

Depending on the needed cap size (based on bps, etc.) the primary
may use various numbers of turns as needed.  It is mostly the
concept that is important here;  keep the surge Z high for lower
gap losses.  If you need a lot of primary turns to tune the coil, then
the wire may be thinner, than if you need fewer primary turns.
>
>  If we want high primary surge impedance, why does everyone concern
>  themselves with using welding cable as tank wiring?

In many cases, the welding cable does no good at all.  The welding
cable could be replaced with a wire of 1/2 the diameter, and the
results would be the same.  But..... the main reason that thick wire
such as welding wire is thought to be needed, is because a low
surge impedance is often used.... and this involves very high
primary currents.  With a high surge Z, the currents are much lower,
and the wire can be thinner.
>
>  Mike Waddick and I compare notes often and he is using the 6x24 with #22 as
>  well. Wouldn't the optimal wire guage be as follows?:
>
>  diameter                guage
>  2                                 34
>  4                                 28
>  6                                 24
>  8                                 22
>  10                               20
>  12                               20
>  14                               18
>  16                               16

I guess here you're looking at the inductance rather than the number
of turns.  It is true that high inductance is what is really needed on
both the primary and the secondary.  Not so much the number of
turns.  But....  if you make the coil super-wide, it will have a lot of
self C and it may need a toroid that is too large for the amount of
power.  So my suggestions take such factors into account.  Overall,
the coil has to be tall enough so it doesn't arc over from end to end,
practical considerations such as that, etc.

JOhn Freau
>
>
>  Just trying to get more bang for my buck,
>
>  -Mike Novak
>

```