[evlatests] EVLA X-Band Behavior

[Rick Perley]

    I used a 4.5 hour dynamic run last night to try a 'hi dynamic range' 
imaging trial at X-band.  Specific results on the imaging will be 
reported later.  This early report is to note three problems:

    The observations were made in mode '2BD', so only IF2 data are 
taken.  (This because antenna 21 works well only on this IF pair).  All 
9 EVLA antennas came up nicely, but ...

    1) Antenna 24 died after only 30 minutes, on both polarizations.  
There is no note on the matter in the operators' log. 

    2) Antenna 21 has a very large delay error:  a full turn over 25 MHz 
bandwidth, translating to about 40 nsec.  The slope translates to an 
increment of 40 nsec being necessary.   Can somebody do this? 

    3) All EVLA antennas, *** except antenna 18 ***, have a large and 
steady phase gradient.  The seven other EVLA antennas (13, 14, 16, 17, 
21 23 and 26) all showed a uniform temporal phase slope of -30 
degrees/hour.  (Antenna 24 was not on long enough to measure accurately 
-- however, for the 30 minutes it was present, the phase dropped at the 
noted rate). 

    Otherwise, data quality is very good in general.  Specific 
exceptions will be noted in later reports.