Hi qrp.ddc,
Thank you very much for clarifying that your bandwidth criteria for measuring Q, using an SWR threshold of 2.618:1, only applies when the SWR at resonance is 1:1.
You might be interested in section 4 of the following document, which describes a more general method of measuring Q of a resonant circuit, be that circuit an antenna, an LCR circuit, or a cavity resonator, etc.
(thanks to Larry Rothman for the link).
If interested, this method has been implemented in Matlab, the downloadable package can be found here:
(The included PDF contains informative examples. If anyone would like a copy and does not want to download the package from Matlab central, let me know and I'll send you a copy of the PDF).
- Jeff, k6jca
