[evlatests] Rubidium update

[Keith Morris]

Almost immediately after my last update, the Rubidium returned to a 
drift rate of approximately 50us/day, most likely due to the change in 
temperature environment after we finished the adjustment and closed the 
rack.  So we found a way to get the serial port connection through the 
Master Rack bulkhead and performed a second adjustment with the Rubidium 
in a constant temperature environment.

Based on the last 1 1/2 hours of data, 1-minute averages, it is now 
drifting with a rate of about 2us/day, with an offset of 4.5us (Rubidium 
leading) from the GPS tick.

A timer/counter has now been installed, measuring the delay between the 
GPS tick and the system PPS tick at the output of the L356.  I am 
arranging with the operators that they will take a counter reading once 
at 8am, once at 4pm, each day, and email me the two readings.  In this 
way we will have adequate warning should the offset or drift rate change 
abruptly.  This is our stopgap solution until we are able to make the 
L356 monitor points more robust.


-- 
Keith Morris
National Radio Astronomy Observatory
1003 Lopezville Rd.
Socorro, NM 87801
575-835-7060 (phone)
575-835-7027 (fax)