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Entry  Tue Nov 10 19:25:42 2015, gautam, Update, General, FS725 Rubidium reference 
    Reply  Tue Dec 22 16:44:03 2015, gautam, Update, General, FS725 Rubidium reference - REPAIRED FS725_repaired.jpg
Message ID: 11750     Entry time: Tue Nov 10 19:25:42 2015     Reply to this: 11898
Author: gautam 
Type: Update 
Category: General 
Subject: FS725 Rubidium reference 

In the last few days, with Koji's help, I have recovered both the FS725 Rubidium references from W. Bridge, one from the ATF lab, and one from the CTN lab. Both are back at the 40m at the moment.

However, the one that was recovered from the ATF lab is no longer locking to the Rubidium reference frequency, although it was locked at the time we disconnected it from the ATF lab. I emailed the support staff at SRS, who seem to think that either the internal oscillator has drifted too far, or the Rb lamp is dead. Either ways, it needs to be repaired. They suggested that I run a check by issuing some serial commands to the unit to determine which of these is actually the problem, but I've been having some trouble setting up the serial link - I will try this again tomorrow. I'm also having trouble generating an RMA number that is needed to start the repair/maintenance process, but I've emailed SRS support again and hope to hear back from them soon. 

The other FS725, recovered from the CTN lab earlier today, seems to work fine and is locked to the Rb reference at the moment. I plan to redo the calibration of the phase tracker with an 'absolute' frequency reference with the help of the FS725 and out GPS timing unit tomorrow. Once that is done, the working unit can be returned to the CTN lab. 

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