I plot beat noise PSD, with estimated H1 arm noise, and SR560 noise converted to frequency noise in the current beat measurement. From the approximation, SR560 noise will be smaller than H1 noise.

 The conversion for SR560 noise to frequency noise is computed by finding the slope of signal from self beat measurement.

parameters are from Frank's entry below

amplified (DC-coupled) signal from mixer using SR560, LP@30Hz, gain20 in channel C3:PSL-GEN_DAQ15

185.0MHz :  -2.405V
154.2MHz :   0.005V
123.2MHz :   2.263V

The pkpk values is then (2.263V - -2.405V)/gain20 = 0.2334 V over 185 MHz - 123.2 MHz = 61.8 MHz range.

Thus the signal is = (0.2334V)/2 sin ( pi df/ 61.8 MHz)

This gives the maximum slope = 0.2334 V* pi /2 /61.8 MHz, or  ~ 170 MHz/V.

SR560 noise is estimated to be flat, 5nV, at high f, a corner at 10Hz which gives 5 uV at 10mHz.

multiplied by 17 MHz/V to get frequency noise from SR560.

load beat_data.mat

%beat_pll_100kHz(:,3)=beat_pll_100kHz(:,2).*sqrt(1+(0.16./beat_pll_100kHz(:,1)).^2);

% correction for 160mHz high pass (AC couple)
beat_pll_100kHz_2(:,3)=beat_pll_100kHz_2(:,2).*sqrt(1+(0.16./beat_pll_100kHz_2(:,1)).^2);
beat1_2011_01_30(:,3)=beat1_2011_01_30(:,2).*sqrt(1+(0.16./beat1_2011_01_30(:,1)).^2);

loglog(beat1_2011_01_30(:,1),beat1_2011_01_30(:,3)*71e3... 
      ,beat2_2010_11_29(:,1),beat2_2010_11_29(:,2)*71e3,...