# Re: Coupling & tuning

```Original poster: "J. B. Weazle McCreath by way of Terry Fritz <twftesla-at-qwest-dot-net>" <weazle-at-hurontel.on.ca>

At 06:53 PM 18/10/01 -0600, you wrote:

>Original poster: "Terry Fritz" <twftesla-at-qwest-dot-net>
>
>Hi J.B.,
>
>Just changing the coupling will not affect tuning.  However, if you move
>the secondary to change the coupling, moving the secondary may affect the
>tuning a little since you are changing the coil's dimensions in space a
>little.  But it probably is not a noticeable change in any case.
>
>If the coupling to too high, you will get racing arcs.  If it is too low,
>you will loose a little streamer power (far preferable over burning up the
>secondary).
>
>In general, about 0.15 seems to work well but best just to play with it
>rather than worrying with the numbers themselves.  Dr. Rzeszotarski's
>program below will calculate the coupling within a percent or two.
>
>http://hot-streamer-dot-com/TeslaCoils/Programs/MANDKV31.ZIP
>http://hot-streamer-dot-com/TeslaCoils/Programs/MANDKV31.PDF
>
>Cheers,
>
>	Terry
>

Hi Terry,

Thanks for the quick response to my query.  I've been playing with
my coupling lately, having used your method to measure the voltage
across the secondary while a known current was passed through the
primary.  Worked slick, I might add!  I found after doing the math
that my coupling was on the low side, about .075, so I measured it
while moving my primary up and down (strange, but it's easier the
way my coil is built than moving the secondary) and settled on the
new measurement of about .12 which seems to be fine from what I've
read.  I was concerned that it might have thrown off my tuning and
I wanted to know which way to go.  Your explanation makes sense.

On another note, I see the great debate on the resistors is still
going on...I'm surprised that I seem to be the only one that has
done the dimmer mod to incorporate the neutral wire which negates
the need for the resistors.  The dimmer I used was a cheapo that
I picked up at the hardware store for a few bucks, and actually I
only ended up using the "chassis" and the triac from it, all other
parts coming from my junk box, including the 20 amp triac, which
is way overkill.  Works great, though.  Thanks for your help.

73, Weazle, VE3EAR/VE3WZL

Listening: 147.030+ and 442.075+
E-mail:    weazle-at-hurontel.on.ca
or ve3ear-at-rac.ca
Web site:  http://www.hurontel.on.ca/~weazle

```