On Sat, 17 Apr 2004 21:05:34 +0100, John Woodgate
posted this:

I read in sci.electronics.design that James Meyer
wrote (in ) about 'A neat
and compact way to generate RF harmonics...', on Sat, 17 Apr 2004:
On Sat, 17 Apr 2004 17:26:15 +0100, John Woodgate
posted this:

I read in sci.electronics.design that James Meyer
wrote (in ) about 'A neat
and compact way to generate RF harmonics...', on Sat, 17 Apr 2004:
IOW, the Q without the probe will be higher than the Q when you insert
the probe to measure the Q.

Use an inductive current pick-off. That how the Marconi Instruments 1245
series Q-meters work(ed).

Nevertheless, *ANY* method used to probe the field associated with the
resonator will load the resonator and degrade the Q.

IIRC, the Marconi unit used a 10 nH inductor (maybe less) made of a
short length of silver wire, gold-plated to eliminate sulfide attack.
The effect on Q would be minimal in the extreme.

But what about the energy extracted from the probe to make the
measurement? Any load on the probe is transformed into a load on the resonator.
Compensating for that load requires a very small number be divided by another
very small number. Any error in either number makes a much larger error in the
result of the calculation.

Jim