On Mon, Aug 8, 2022 at 04:19 AM, G8HUL wrote:
I seem to recall that most of the R&S LCR meters also measured Q, can't recall the tolerance on the measurement.
73
Jeff G8HUL
If they are anything like my HP 4284A and 4285A Precision LCR meters, the uncertainty of Q is
extremely high for a Q of 20 or more.
An example from the 4285A user manual
L = 220 nH (measured)f = 25.2 MHz
Q = 30 (measured)
Uncertainty +106/-13, so the actual Q is between 17 and 136.
I think the Practical Wireless design I attached is pretty poor, but I think even that would be more accurate. Those figures above are a reactance of j 34.8 ohm and a resistance of 1.16 ohm. The 2 ohm injection resistance in the PW design would introduce a significant error - much more so than resistors of 20 milli ohm used by Boonton, HP and Marconi. But I think even the PW design would not be as bad at Q measurements as the 4285A Precision LCR meter.
Dr. David Kirkby, Kirkby Microwave Ltd