[evlatests] Novmber 10 2005 mystery

[Ken Sowinski]

                       EVLA Tests, November 11 2005

At the beginning it was too windy to point antennas so I spent
the time looking at sampler statistics and T5 TP and SD for all
bands and IFs with the intent of trying to correct the power
in to the sampler for the various downconverter swaps in the 
last week or two.  This was done with the deformatter gain 
parameter set to 30.  Only 14A has a 6 dB pad on the deformatter
output; all the rest have 10 dB pads.  Is there any reason not
to change them all now?

1.  14D was too low at all bands.  The downconverter settings
were all reduced by 3 dB.
2.  16A was too high at most bands.  The downconverter settings
were increased by 4-6 dB.
3.  There are no cals for C band on antenna 16.
4.  Antenna 16 is connected to something when Q band is selected.
Remember to check the switching when the Q band receiver is installed.
5.  There was some evidence that 14D was not very stable.

After a while the wind calmed enough to point antennas, however I 
might have been happier had it not.  Antennas 14 and 16 cheerfully
fringed at all bands but neither one worked with a VLA antenna.
I checked the obvious things but was unable to find out why.
1.  The SSLO for EVLA antennas when looked at for X band was exactly
what I expect.
2.  Disabling phase switching made no difference.
3.  All the executors I could easily find behaved the same way.
4.  There was no hint of correlated signal even with very short
integration times; with or without phase switching.
5.  It is possible, but unlikely, that the EVLA system has the wrong 
idea about time, but it has to be a very far wrong.  
6.  It is possible that the two systems are doing fringe rotation
referred to very different places.  I could not easily check that
but verified that the VLA antennas were being commanded with reasonable
fringe frequencies.
7.  I used only the ?sysstart.py scripts.
8.  Rick pointed out that this happened before but could not remember
what we did then to make it work.
9.  The last time it worked was Wednesday afternoon.