[evlatests] VLA image -- and an interesting clue ...

[Rick Perley]

    I calibrated the VLA data, taken simultaneously with the WIDAR test 
data. 

    The images are very nice, with loads of the expected background 
sources. 

    I then returned to the WIDAR images, specifically the set of 'noise' 
images (blank field).  There are three, made with 1, 10, and 100 MHz BW 
each. 

    The peak background source in the 1 MHz wide field is 11.2 mJy
    The same object in the 10 MHz field is now only 7.1 mJy
    The same object in the 100 MHz field is now essentially invisible, 
at 1.2 mJy! 

    The VLA dataset shows this background source at 17  mJy.

    For the VLA correlator dataset and the WIDAR 100 MHz dataset, the 
expected thermal noise limits should be about the same  -- and they are, 
at 0.15 mJy. 

    From this, I'm guessing that the act of coherently summing over the 
bandpass is actually destroying the signal (but not the noise).  
Something is backwards?