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Entry  Mon Jul 7 21:36:33 2014, Jenne, rana, Update, PSL, PMC local oscillator is going wonky PMC_LO_failing.pdf
    Reply  Mon Jul 7 22:18:26 2014, Koji, Update, PSL, PMC local oscillator is going wonky 
       Reply  Tue Jul 8 15:28:32 2014, Koji, Update, PSL, PMC local oscillator is going wonky 
          Reply  Wed Jul 9 00:47:22 2014, Koji, Update, PSL, PMC local oscillator is going wonky 
             Reply  Wed Jul 9 11:41:12 2014, Koushik, Update, PSL, PMC local oscillator is going wonky 
                Reply  Wed Jul 9 19:53:34 2014, rana, Update, PSL, PMC LO monitor trend (5 years) LODET.png
                   Reply  Thu Jul 10 01:02:13 2014, rana, Update, PSL, more PMC science PMCloCal.pdf
          Reply  Wed Jul 9 00:59:09 2014, rana, Update, PSL, PMC local oscillator is going wonky PMC_RFslider.pdf
Message ID: 10160     Entry time: Wed Jul 9 00:59:09 2014     In reply to: 10153
Author: rana 
Type: Update 
Category: PSL 
Subject: PMC local oscillator is going wonky 

Quote:

Koushik and Koji try to fix the PMC oscillator issue. So we remove the module from the rack.
This means we don't have the PMC transmission during the work.

 After the ERA-5 was replaced (see Koushik elog) we relocked the PMC.

The new LO level going into the PMC servo card is +11.5 dBm. The LO mon on the PMC card reads 9 dBm and seems so flat I now suspect the monitor circuit.

I also measured the RF drive to the EOM as a function of C1:PSL-PMC_RFADJ on the Phase Shifter screen.

The phase shifter slider gives ~75 deg/V in phase shift of the RF out to the EOM. I tried to optimize the loop gain quickly using the fluctuations in the reflected power. The loop oscillates at high frequency with the slider at 21 dB and also at 9 dB. So I set the gain at +14 dB. Needs to be optimized correctly in the daytime.

 

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