I took beatnote measurements and spanned gain values (COM and FAST) on South side to see the variation in beatnote with them.

Method

• I used BNspec.py with default settings (10 kHz bandwidth at 15.625 kSa/s for 60s) while spanning the parameter space of NFSS gains.
• Every time the gain values are changed, a gainCycle.py is done and script waited for 10s before attempting beatnote measurement to let loops settle down.
• The beatnote frequency was robustly within 2 kHz of 27.34 MHz during this whole measurement.
• Overall experiment was run by spanParamSpace.py script.

Inference

• I calculated the integrated total beatnote frequency noise in the frequency range 200 Hz to 1 kHz where the total noise is expected to be dominated by coating Brownian noise.
• Unstable regions in the parameter space are clearly visible.
• But as to the stable region, once the loop gets onto that, the noise does not change much, similar to North side.
• So here as well, it seems like the beatnote noise is largely independent of the gain settings.
• I'm unsure if I should look at this and the last measured data sets differently. Maybe I'm missing something.

Data