[evlatests] EVLA stability and performance

[Rick Perley]

    All bands were checked last night, using continuum-only 
observations.  The primary focus was on system stability, so most of the 
time was spent on a strong source at X-band.  These observations were 
done under Modcomp control. 
    In general, the data quality was very good.  All 10 EVLA antennas 
worked stably, on at least two IFs each.  Antenna 17 died (slowly) at 
0:32:48. 

   A)  Key Results:

    *  The ten-second phase drops previously noted on antennas 19 (B and 
C) and 24 (B and D) are now gone, as a result of changes made yesterday. 
    *  The 'sinusoidal phase' with ~1 minute period, remains on 21A and 
B.   It is not present all the time -- it 'comes and goes', looking 
rather like a wave packet ...
    * 21 C and D is dead at all bands. 
    * The 10-second parabolic phase residual remains on long baselines 
(as expected). 
    * The 'short shallow drops' are present, on antenna 18, 19, 21, 23, 
24, and 26.   Note that these drops were not seen on 13, 14, 16, or 17.  
Curious numerology ...

    B) Secondary Issues:

    * Antenna 14, IF 2 (B and D) has very unstable amplitudes at 
X-band.  These are clearly related to large changes in reported system 
temperature (variations in reported Tsys up to 40K are noted). 
    * Antenna 26B is also very unstable -- and its Tsys also shows large 
variations.  (But 26A is o.k.). 

    C) Band-Specific Issues:

    * P-Band:  Antennas 17, 24, and 26 gave no fringes.  They have 
receivers, so something is broken. 
                      Antenna 14 gave no fringes in IF1 (A and C). 

    * L-Band:  All antennas worked (other than 17 dying, and 21CD dead). 

    * C-Band:  No fringes from 23, which is claimed to have a receiver.  
19 and 21 have no receivers. 

    * K-Band:  Everything worked!  Good data. 

    * Q-Band:   No fringes from 26 B and D.  Both antennas 23 and 24 
failed on one scan -- no cause known.   Antennas 17, 19, and 21 have no 
receivers (and gave no fringes!)