Using the Rubidium, August 2008

Using the Rubidium backup frequency standard, August 2008

During August 4 to 6, 2008, the Sigma Tau Maser was taken off line for repairs. During this time the rubidium standard was used as the alternate frequency and time standard.

The Sigma Tau Maser was off-line August 4 at 12:27 UT until Aug 6 at 15:47 UT.

Time was referenced to the Rubidium Aug 4 at 15:03 UT until Aug 6 at 15:09 UT.

Plot of Site Time vs GPS clock offsets - Aug 4-7.

Clock offsets during August (hourly medians)

Clock offsets Aug 4-6 in pulsar format (hourly medians)

Here is the procedure for switching the frequency standards.

1	Use the 2 rotary switches on the "Frequency Standards Switching Network" in the right-hand timing rack to select either H maser or Rubidium.
2	Connect the 5 MHz input cable of the TRAK master clock to the desired standard.
3	Re-sync the TRAK master clock to the GPS tick, and reset the time. (Consult the TRAK manual on how to do this)
4	Re-synchronize the 5MHz/1pps for the LO1 system (must be done at the receiver room).
	Note: if one is using the rubidium to avoid the 28Hz sidebands of the Sigma Tau maser, but otherwise the ST maser is working ok, then DO NOT do steps 2, 3, or 4 !!