[evlatests] X-Band performance last night

[Jim Jackson]

At 09:58 AM 4/11/2007, Rick Perley wrote:
>- The phases on all four IFs undergo a sinusoidal variation,
>of amplitude 30 degrees, and period about 90 seconds.  All four vary
>with the same phase (i.e., they rise and fall together).  Other than
>this variation, the phases behave normally.


This may be the clue we needed.  During the testing we were doing back in 
Jan/Feb, Rob, Keith and I saw this odd behavior in the L304 optical 
receivers when the optical level was high (even in the upper end of the 
specified operating range).  When I plot the monitor point in the L304 for 
512MHz total power, it does appear to be oscillating up and down slightly 
at a slow rate.  I just asked everyone involved and no one remembers 
setting the optical levels into the L304 on Ant 21 - it will definitely be 
too high if an attenuator was not installed. Jerry and I will check it 
tomorrow morning.

We are now also seeing occasional alarms from the L302-1 (IF's AC) 
indicating it may be unhappy with the heartbeat it is getting from the L305 
- we'll check into that tomorrow as well.  However, the module doesn't seem 
to be having the lock problems that usually go along with a missing 
heartbeat.  If one side of that LVDS timing signal is missing, I suppose it 
could be causing the module's timing to be a bit erratic.

Jim