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Entry  Fri Feb 4 11:10:27 2011, Suresh, Update, Green Locking, VCO PLL Frequency noise VCO_calibration.pngVCO_PLL_Servo.pngVCO_Gain.pngVCO_Transfer_Functions.pngVCO_PLL_Freq_Noise.png
    Reply  Mon Feb 14 00:39:21 2011, rana, suresh, Update, Electronics, VCO Frequency Noise Measurement with the MFD 
       Reply  Thu Feb 17 23:11:40 2011, rana, Update, Electronics, VCO Frequency Noise Measurement with the MFD vco.png
Message ID: 4281     Entry time: Mon Feb 14 00:39:21 2011     In reply to: 4248     Reply to this: 4318
Author: rana, suresh 
Type: Update 
Category: Electronics 
Subject: VCO Frequency Noise Measurement with the MFD 

We hooked up the VCO Driver output to the MFD. We adjusted the levels with attenuators to match up to the Level 7 mixer that's being used.

The mixer the input to the SR560 is going in to the XARM_COARSE_OUT channel and the SR560 (AC coupled, Low Noise, G=1000, LP@1kHz) 600 Ohm output goes into XARM_FINE_OUT.

We calibrated these channels by putting in a 10 mVpp sine wave at 0.22 Hz into the Wideband Input of the VCO Driver box (which has been calibrated to have 1.75 MHz/V for f < 1.6 Hz). This should correspond to 17.5 kHz_pp.

To increase the sensitivity, we also added a 140 ft. BNC cable to the setup. We also added some extra short cable to make the overall phase shift be ~90 deg and zero out the mixer output.

I used the time series data in DTT to then calibrate the channels by changing the GAIN field in their filter modules. So now the DAQ channels are both calibrated as 1 count/Hz.

 

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