[Amps] Measuring Q with an SWR analyzer

[Peter Chadwick]

Bill asks:
>From this is it possible to calculate the Q of the tank circuit? 
Obviously, the higher the Q, the smaller the 2:1 SWR bandwidth, but 
is it possible to calculate it exactly?<
Yes. The accuracy depends on the accuracy of the measurement of the 2:1 VSWR, and the frequency.
Now, deriving the actual equations needs more consideration: the problem is that you know the SWR, but not actual impedance, so you're starting from a circle on the Smith chart, not a point.
As the math text books say, 'derivation is left as an exercise for the reader'.
An easier method would be to feed a signal in and measure the volts across the load resistor with a RF voltmeter (VTVM!) or 'scope or whatever, and measure the frequencies where the volts has dropped to 0.707 of the volts at resonance.
73
Peter G3RZP