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Entry  Wed Apr 22 17:29:14 2020, gautam, Update, PSL, FSS debugging attempts FSSspec.pdf
    Reply  Thu Apr 23 10:42:02 2020, rana, Update, PSL, FSS debugging attempts 
Message ID: 15312     Entry time: Thu Apr 23 10:42:02 2020     In reply to: 15310
Author: rana 
Type: Update 
Category: PSL 
Subject: FSS debugging attempts 

I had set up the 4395 to do this automatically a few years ago, but it looked at the FSS/IMC instead. When the PCDRIVE goes high there is this excess around ~500 kHz in a broad hump.

But the IMC loop gain changes sometimes with alignment, so I don't know if its a loop instability or if its laser noise. However, I think we have observed PCDRIVE to go up without IMC power dropping so my guess is that it was true laser noise.

This works since the IMC is much more sensitive than PMC. Perhaps one way to diagnose would be to lock IMC at a low UGF without any boosts. Then the UGF would be far away from that noise making frequency. However, the PCDRIVE also wouldn't have much activity.

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