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Re: [TCML] Tuning primary to secondary with a scope
On 3/21/12 8:12 AM, Colin Heath wrote:
This is the reason scope tuning is of little value for accurate tune at high power.
By all means use scope to tune ballpark then full power runs followed by small primary tap changes is the way to dial in the final tune. Keep in mind this will change every time you run the coil in different surroundings.
I thought you classic coil boys would be against all this modern scope stuff anyway ;)
No.. I insist on a very detailed finite element model of the coil and
the surroundings on a 1 mm grid before I even apply power. And then I
insist that we measure the line voltage to 0.1 Volts and apply carefully
modeled losses and inductive effects of the extension cord, the variac,
the primary, the gap losses, etc.
But seriously.. Colin is right.. a scope or tuning aid helps get you in
the ballpark so the manual tune process takes less time. That whole
sequence of "turn off the power, disconnect the cord, make sure the
system is discharged, move the tap a tiny bit, remove the grounding bar,
plug in the cord, turn on the power gradually with the variac, estimate
the spark length" is really tedious.. And because it's tedious, there's
a *real strong* tendency to start to short cut it.. why unplug, I can
just turn off the plug strip.
why bring up power slowly, just hit it with full power each time.
why bother putting the grounding hook on when you know it's off.
and pretty soon, you catch yourself reaching to adjust something when
it's live, and you realize you've cheated death by microseconds, saved
by the arc to the grounding stick telling you the 50 cent switch on the
power strip has failed shorted.
So things that can sort of speed up the process and reduce the tedium
are *good ideas*
It also is nice when you're making radical changes in the configuration.
(There is a parallel with "pruning antennas to resonance".. a heck of a
lot easier with a impedance analyzer, even easier with a VNA )
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