[evlatests] Table of PDif compressors

[Rick Perley]

    I reported yesterday some evidence which points to the T304 as the 
origin of our PDif compression problems. 

    Here I present a simple table of the fractional compression for each 
antenna-IF that had good data, and was in the array Saturday night.  The 
listed values are of:  PDif(Cyg)/PDif(coldsky).  Cygnus A increments the 
total power by a factor of about 6 dB.  The attenuators were set on cold 
sky.   The two subbands utilized were turned to 1381 and 1756 MHz (lower 
edge) with 128 MHz BW.

Antenna      CompressionRatio
                      A       B     C     D
----------------------------------------------------
    3               .92   .96   .75   .88
    4               .80   .87   .77   .85
    5               .75   .76   .59   .72
    6               .92   .70   .86   .85
    7               .96   .95   .96   .94     
    8                 X   .95   .91   .94     
    9               .85   .88   .90   .93
    10               X   .72   .92   .88
    12             .92   .90   .92   .95
    14             .99   .93   .94   .94
    16               X   .90    X    .88
    17             1.0  1.0    .96   1.0
    18             .88   .82   .64   .81
    20             .93   .90   .92   .85
    21             .76   .87   .75   .77
    25             .50   .64   .55   .65
    27             .99   .98   1.0   1.0
------------------------------------------------

    I suggest that we look at the monitor data (attenuator settings, 
power levels, etc.) for the best and worst antennas given above, to find 
if my claim that the antennas with the highest PDif compression also 
have the highest total powers within the T304, and vice versa. 
    The 'poster child' antennas, with the best performance (least 
compression) are, in order:
         17, 27, 7 and 14.  
    The candidates for reform school are (worst first):
         25, 5, 21, 18.