[evlatests] EVLA tests, Sept 8 2005

[Ken Sowinski]

                        EVLA Tests, September 8 2005

It was such a confusing day it is hard to say what was done or
learned.  Communications with 14 were lost yesterday and today 
it was found that the inverter which powers the network swich had 
died during a thunderstorm.  Once it came back 14 still did not 
work for a while because tne MIBs in all four DTS modules were not
responding.  Antenna 16 was sort of working during this time.
The 16B donwconverter was reset and Rick's sesnitivity tests was
run during lunch.

After lunch an attempt was made to get as much as possible to work.
Two more nonresponding downconverter MIBs were found: 16A and 14B.
After a little more struggle the cause of the weak correlation was 
found to be faulty phase switching.  Just as I was about to investigate
different time offsets to the L302 16 began to work again.  Without
any intervention by me.  If this was not caused by people working in
the control building it is the most important thing learned today.

What happens is that at random times antennas 14 and 16 cease to 
correlate well against VLA antennas but continue to correlate 
reasonably well against each other.  The most straightforward 
explanation is that the L302s, all of them!, lose the correct idea
of time at the same time, and, if we are patient enough come back
again when they feel like it.  I am hoping that someone will confess
to causing this by disturbing something in the control building.

There is a pointing run scheduled for tonight which will be done at
X band and include EVLA antennas.  George's polarization tests following
that will also use EVLA antennas.