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Entry  Fri Jan 9 14:01:17 2015, manasa, Update, General, AUX Y + PSL beat note at 1064nm 
    Reply  Tue Jan 13 10:28:02 2015, manasa, Update, General, AUX Y + PSL beat note at 1064nm 
       Reply  Tue Jan 13 13:22:54 2015, Jenne, Update, General, AUX Y + PSL beat note at 1064nm: needs work 
          Reply  Tue Jan 13 14:01:20 2015, manasa, Update, General, AUX Y + PSL beat note at 1064nm: needs work 
Message ID: 10895     Entry time: Tue Jan 13 14:01:20 2015     In reply to: 10894
Author: manasa 
Type: Update 
Category: General 
Subject: AUX Y + PSL beat note at 1064nm: needs work 
Quote:

I'm super excited about this new frequency readback, but I'm not sure that it's reliable yet.  Without touching any settings, the readback is currently saying 78.6MHz, and is changing slightly (as is the FSS Slow Temp), so something is working.  However, the beatnote as measured on the spectrum analyzer is 158.2MHz.  So, either the calibration or the tracking or something isn't quite finished being tuned yet.

It's going to be super awesome when we have this though!!

As Jenne pointed out, this is still not fully tuned. 

For example, I found today that the frequency counter requires more power at the input >= -20dBm to measure frequency inputs < 40 MHz. Since the RFPD gives ~ -40dBm at its output, the ~20dB gain amplifier will not be enough to measure low frequencies in case the beat power at the PD drops (which is very much possible when the alignment drifts or things move around on the PSL table).  So I am shopping for an RF amplifier with higher gain to replace the current one. In the meantime, I will test the PID loop for set point frequency > 40MHz.

I have also observed the frequency difference between the measured frequencies on FC and the spectrum analyzer. I am not sure where this comes from as yet. 

At this point, the FC readout is only reliable enough to find a beatnote that is lost on the spectrum analyzer.

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