[evlatests] EVLA System Check, 25 Oct

[Rick Perley]

    30 minutes was used this morning to check overall EVLA performance. 

    Setup was standard spectral line.  Referenced pointing (both primary 
and secondary) was utilized to peak up antenna gains. 

    Overall, the EVLA is in pretty good shape.  Brief specifics follow. 

    Global statements:

    Antenna 16 A and C is dead -- bad L302 which is to be replaced today. 

    A) L-band. 

    Antennas 14, 18 and 24 were out for various reasons.  (All appear 
later). 

    Antennas 13, 16 (BD), and 26 fringed. 
    Sensitivities of 13 and 16 were normal.
    Sensitivity of 26A was normal, but B, C, and D were all terrible. 

    The bandpass solutions gave the needed delay corrections for 26:

    -83, -70, -70, and -40 nsec for IFs A, B, C, and D. 

    If the EVLA convention is the same as the VLAs, then these numbers 
must be *subtracted* from the current values. 

    B)  C-Band. 

    Antenna 14 was out of the array during this scan. 
    Antenna 13 was badly misbehaved -- high noise, weak signal, terrible 
sensitivity.  Tsys on 13 AC was ridiculous, but normal on BD.  I have no 
idea what is wrong. 
    Antennas 16 (BD), 18, and 24 gave fringes. 
    Antenna 24 sensitivity was good on AC, but terrible on BD. 
    Antenna 26 has no C-band receiver. 

    C) X-Band

    Antenna 14 returned by this time.

    All six EVLA antnnas gave fringes. 
    Antenna 26 pointing is off 1 arcminute in Azimuth. 
    All antennas gave very high Tsys -- 70 to 90 K!  (Really thick 
clouds?) 

    Sensitivities of EVLA antennas are like VLA antennas in general, except:
       16 was low (BD)
       24 was low on AC, and terrible on BD
       26 was terrible in IFs B, C, and D.  But 26A is normal! 

    D)  K-Band

    Antennas 13 and 26 were bad on all IFs.  Secondary referenced 
pointing failed on these two antennas -- hard to tell if the pointing is 
bad, or the antenna sensitivity is so bad that pointing failed. 
    Sensitivity for 14 was excellent, 18 was good, and 16 (BD) a bit 
lower than optimal.  Sensitivity for 24 is truly terrible. 

    All Tsys values are very high -- over 100 K, except for antennas 6, 
14, and 22 (which are no where near adjacent), which are ~60 -- 80 K. 

    E)  Q-Band. 

    Antennas 13 and 26 were dead (and referenced pointing failed).  26 
has no receiver?.  13 is a troubled antenna at all bands except L.  
There is nothing in the operator's log to give a clue.  Secondary 
referenced pointing (using X-band values as primary) worked on 14, 16, 
18, and 24.  Good job! 

    All other antennas worked well! 
   
    Sensitivity of 14 is very good, 24 is o.k. on AC, terrible on BD.  
18 is low on AC, o.k. on BD. 

    There are no believable Tsys values for any EVLA antenna.  All VLA 
Tsys values were very high -- over 100 K.