[Lowfer] Measuring high Q

Thu, 20 Nov 2003 23:27:24 +1300

What sort of Q values do you typically get  for the Tesla coil secondaries
Ed? Obviously they will be high, but I wonder just how high?  Hope to find
out for myself sometime- I have a couple of old neon xfmrs here somewhere
just waiting for that magic day when I have nothing else to do!!
Dave
ZL3FJ

----- Original Message ----- 
From: "Ed Phillips" <[email protected]>
To: <[email protected]>
Sent: Thursday, November 20, 2003 2:20 PM
Subject: Re: [Lowfer] Still looking for a capacitance dissapation factor
test

> Dave Brown wrote:
> >
> > Bill
> >
> >  Yes- I'm finding that measuring Q when it's higher than about 500 or so
is
> > quite challenging- and I've had similar issues with a Tek probe as well.
I
> > guess as long as one can characterise all the test gear correctly it's
> > possible to compensate readings but it seems to be bordering on the
> > uincertainty principle sometimes!
> >
> > 73
> > Dave
> > ZL3FJ
>
> I've had good luck estimating RF resistance by a substitution method.
> For low-Z (L/C) circuits connect them in parallel resonant circuit and
> feed them through a resistance at least as large as their parallel loss
> resistance.  Measure voltage at resonance, remove the circuit, and
> substitute resistors until the voltage is the same.  (You have to be a
> little careful about the generator waveform.)  For high-Z circuits
> connect them in series resonance and do the same thing, although with a
> much lower series resistance in the generator lead.  The method seems to
> work pretty well for loading coils and Tesla coil primaries (low-Z) and
> secondaries (high-Z).
>
> Ed
> _______________________________________________
> From the Lowfer mailing list
> Send messages to: [email protected]
> To sub/unsub visit: http://mailman.qth.net/mailman/listinfo/lowfer
>