[evlatests] Compression tables

[Rick Perley]

    A noontime test of the PDif compression on Taurus A ran today.  I 
tried all frequency bands.  Compression was seen up to and including 
K-band.  The primary beam, combined with the spectral slope of the 
source and the higher system noise combine to make the power increment 
too small to be useful at Ka and Q bands. 
    The increment to system temperature caused by the source is 
approximately:

    60K at L, S, and C bands. 
    40K at X band
    25K at Ku-band
    10K at K band. 

    In this, and succeeding messages, I'll give the 'compression factor' 
for each of these bands, for each IF and antenna.  This is defined as:  
(PDif on Tau A)/(PDif on cold sky).  Values are in percent. 

    In this message, I give the L-band values.  The data were taken with 
128 MHz BW, at 1465 and 1820 MHz.  

Antenna        A           B            C             D
-------------------------------------------------------
    1              88         90           93            91
    2              93         92           89            83
    3              99         97           92            91
    4              94         92           88            90
    5              97         98           96            94
    6              98         93           94            97
    7              97         98           97            96
    8              93         95           97            92
    9              97         95           99           100
    10                      in the barn
    11            99         97          98            100
    12            97         97          97             97
    13            98         85         100            89
    14            99         96          96             95
    15            99         96          97            100
    16            96         92          95             93
    17           100       100         97            100
    18            93         89          84             81
    19              very noisy data
    20            93         94          93             93
    21            87         88          93             86
    22            95         95          91             90
    23            89         94          88             92
    24            91         91          98             98
    25            67         67          82             82
    26            93         93          94             94
    27            99        100         99            100
    28            99       noisy       96             noisy
------------------------------------------------------------
   Comment:  Except for a few antennas (notably ea25), the compression 
is rather small, and very uniform amongst the antennas.  The compression 
is definitely much less than for Cygnus A at this frequency -- the ratio 
of the fluxes is about 1.6:1 (1513 Jy for Cyg A, 930 for Taurus A).  The 
notable difference in compression may be a manifestation of the 
nonlinearity in the response.