[evlatests] Quick EVLA System Check

[Ed Fomalont]

INSPECTION OF AM889 on SEP 08, 2007

1.4 GHz, 2 IFs, 2 Pols usual deep field correlator setup,
5 hour experiment

SUMMARY:  Experiment quality is good
           Some interference for 20 min, mostly IF 1
           Problems with ante 11,14,18 are already known
           Correlator offsets becoming more serious
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Antennas out:  1, 25

Interference:  About 30 min on IF1 predominantly

Amplitude stability:
     All antennas/IF/pols with reasonable sensitivity
        ante 20 IF1 R 25% down, IF2 L 25% down.

   PROBLEMS:
        ante 17, all if's, pols.
            Occasional 30% loss of signal for one 3.3 sec integration

Phase stability:
     Little atmospheric/ionospheric variation.

    PROBLEMS:  Ant 14 usual problems - flagged
               Ant 11, 18 phase changes of 70 deg (dual state)
                  IF 1 only
               50 deg phase drift over 5 hours between
                  EVLA and VLA antennas
Imaging:

    CORRELATOR OFFSETS ARE BACK AGAIN

                                  ORIGINAL IMAGE     CORRECTED IMAGE
        rms noise near edge          38 uJy              33 uJy
        rms noise near center       120 uJy              44 uJy


    Corrected image obtained by subtracting average correlator offsets
    over 5 hour run.  Could do better, but does help alot.  Also, needs
    self-calibration.