[evlatests] EVLA Status Check

[Rick Perley]

    The all-bands, fast-change test done yesterday provides a chance to 
check the performance of all the bands.  Below is a short summary of 
problems noted, by band. 
    All antennas were in the array, except ea16, which is in the barn. 
    For all bands, absolute bandpass spectra were derived.  The 
resulting spectra (spectral power levels) are useful in giving a clue to 
whether the power levels to the samplers are correct.  This method is 
not infallible -- the spectral power from the source will also be low if 
the receiver system temperature is unusually high. 

    A)  L-band. 
       No fringes from antenna 17 or 26, as expected (no receivers).  
Fringes were obtained from 15 -- this is marked as 'out for repair' on 
the Monday morning meeting summary. 
       Unusual spectral power levels found in:
           Antenna 12, IFs B and D:  5 dB low.
           Antenna 15, all IFs:  5 dB low. 
           Antenna 27, IFs A and C:  5 dB low. 
       Antenna 13 has a hugely sloped passband -- at the high frequency 
end the spectral power is about 20 dB below the other antennas. 

    B) S-band. 
        Fringes found from 10 of the 11 antennas claimed to be 
equipped.  Still no fringes from 22 (marked as 'out for repair'). 
        Unusual power spectra found in:
            Antenna 14 in RCP  (IFs A and B):  12 dB too low.
            Aantenna 27, in IFs A and C:  8 dB low. 

    C)  C-band.
         No fringes from antenna 13 -- no receiver. 
         Antenna 24 failed to give fringes, on all IFs, for one of the 
three observations. 
         Unusual spectral power levels seen in:
               ea07:  5dB low on Ifs B and D
               ea08:  5 dB low on IF D
               ea10:  10 dB low on IFs A and B (RCP)
               ea12:  low on all four IFs, especially A (15 dB low), and 
D (8 dB).
               ea14:  15 dB low on all four IFs
               ea17: 5 dB low on Ifs B and D, sloped passband to boot.
               ea22:  5 dB low on Ifs A and B
               ea26: 5 dB low on B and D
               ea27:  10 dB low on IFs a and C

    D) X-band
          All antennas fringed on all three scans.
          Spectral power notably low on:
              ea20 (7 dB)
              ea22  (10 dB)
              ea27  (5 dB)

    E)  Ku-Band
          All seven antennas currently equipped fringed.  But...
           - antenna 14 failed to tune on BD side (12 to 13 GHz).
          Unusual spectral power from:
            ea07, IF B:  10 dB low
            ea12:  IFs B and D:  5 dB low
           ea14:  IFs B and D:  25 dB low  ************************  
Note this one!!!
            ea22:  15 dB low on all four IFs
           
    F)  K-Band
           No fringes from antenna 22 (out for repair?)
           ea13 and ea25 gave no fringes on BD IFs (18 to 19 GHz)
           ea13 failed to tune twice (out of three scans) in IF A/C. 
           ea 20 and ea26 failed to tune on one scan on BD IFs. 
            Unusual power density seen only on:
              ea12:  low by 10 dB on IFs B/D. 

    G)  Ka-Band
               No fringes from antennas 7, 13, and 22.  (They were 
expected on antennas 7 and 22). 
              Unusual power density levels:
                 ea03:  15 dB low on all IFs
                 ea06:  10 dB low on IF B
                 ea10: 10 dB low on IFs A and C
                ea18:  10 dB low on IFs A and C
                 ea20:  5 dB low on all IFs
       
    H)  Q-Band
               No fringes from antennas 3, 13, or 22.  Antenna 17 was 
very slow to 'lock on' -- only the last 5 seconds of each scan (45 
seconds) gave fringes, on all IFs. 
                Abnormal spectral power density from:
                  ea23:  10 dB low on IFs B and D (43 -- 44 GHz)  Low by 
5 dB on A and C (48 -- 49 GHz)
                  ea24:  5 dB low on all IFs.  (Could be pointing?)
                  ea27:  15 to 20 dB low on IFs A and C (48 -- 49 GHz).  
Not pointing, since B and D look fine.