[evlatests] L and S band effective sensitivities

[Rick Perley]

    Yesterday's 'solar' test included an observation on and off Cygnus 
A.  So although the solar part of the trial completely bombed, we have 
been able to extract some useful information from the on/off Cyg A. 

    The ratio of the powers between 'on cyg' and 'off cyg' gives a 
measure of the ratio 'efficiency/Tsys'.  We expect a ratio between 4 and 
4.4 for the known values of Cyg A flux, antenna efficiency, and receiver 
temperature at L-band, and values near 3.0 for S-band. 

    The observed ratios are typically in the expected range.  But some 
antennas are discrepant.  These are:

    A)  L-Band

    Antennas Too Good (!)  We like these antennas -- the high ratio 
probably indicates an especially good receiver, rather than an 
especially efficient antenna ...

    8, 18, and 23.  (Antenna 23 is definitely the poster child, being 
25% better than the nominal).

    Antennas Way Bad:  (Defined as having ratios low by 50% or more).  
These guys need attention, as either the system temperature is far too 
high, or the efficiency is way too low.

    7 -- low by 40%
    15 -- low by 60%
    27 -- low by 50%, and unsteady as well. 

   
    B)  S-Band

    Two antennas are notably worse than the others:

    9:  It is low by ~50% at the lower frequency (2500 Mhz), but near 
normal at the upper (3500 MHz)
    27:  Very strange result, with two times too good a ratio in RCP at 
2500 MHz, but half the expected value in the other 3 IFpairs ...