I did a calibration measurement for the Y part of the BeatBox using a Marconi. This is in order to get a more accurate calibration for the arm cavity scan measurement.
The calibration factor I found is:
C1:ALS-BEATX_FINE_PHASE_OUT 50.801 +/- 0.009 deg/MHz
During my cavity scan measurement, I had recorded the beat frequency and amplitude from the Spectrum Analyzer at each zero crossing.
I connected the Marconi to the RF in of the Y part of the BeatBox, and I set the Marconi carrier frequency at one of this zero-crossing frequency that I had recorded, while I set the amplitude in way to have on the spectrum analyzer the same beat amplitude that I read during the measurements or, equivalently, in order to have C1:ALS_BEATY_FINE_Q of the order of 1200 (which is the same value I had during my measurements).
I started with
Then I monitored the C1:ALS_BEATY_FINE_I on the oscilloscope and I adjusted the carrier frequency so that I had zero signal on the oscilloscope. Eventually the frequency corresponding to the zero crossing was 79.989 MHz.
I resetted the phase (clear history in the BEATY_FINE_PHASE panel) and I started changing the frequency by steps of 0.2 MHz, and I spanned about 70 MHz (from 32 to 102 MHz).
The calibration coefficient I found is not so different from the one that Yuta measured (elog 8199).
Here are the fit parameters:
y = a + bx
a = -4239.7 +/- 0.6 deg
b = 50.801 +/- 0.009 deg/MHz