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Message ID: 3423     Entry time: Fri Aug 13 20:58:20 2010
Author: Jenna 
Type: Summary 
Category: Electronics 
Subject: Rubidium clock phase noise measurement 

 Here's an overview of the rubidium measurement:

rubidium_diagram.png

HPIM3871.JPG

 

HPIM3880.JPG

 We have two SRS FS275 Rubidium clocks which are locked together using the built-in PLL through the 1pps input/output. The default time constant for this locking is 18.2 hours because it's designed to be locked to a GPS. We changed this time constant to .57 hours (as decribed in this elog entry) to get the clocks to more reliably lock to each other. We then mix the 10MHz outputs together using a 7dbm mixer (see elog here and picture below)

HPIM3872.JPG

 

The signal then goes through an AC-coupled SR560 with a gain of 100 and LPF at 10kHz, and is then fed into the DAQ. In the first picture below you can make out what all the lights are labeled, and in the second you can see what lights are on. I couldn't get a picture that did both in one, sadly.

HPIM3878.JPG

HPIM3876.JPG

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