[evlatests] More on Zero PDifs

[Rick Perley]

    I sent yesterday a list of antennas which had zero-mean switched 
power. 
    I reviewed today an earlier test, taken on 25 August with the same 
script. 
   
    There are two differences between the 25 August and 16 September data:

    1) PDif was non-zero (i.e., working as expected) on ea27 at all of 
the observed bands,
    2) ea23, at K-band, was working correctly on 25 August, but not on 
16 Sept. 

    All other 'zero PDifs' reported below were also zero on 25 August. 

    
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   There are some antennas which provide zero mean PDif data -- 
meaning, the PDif values are just random noise with a zero average.  
This is a significant problem, since we cannot then use the monitor data 
to determine and correct antenna electronics gain changes, or monitor 
system temperatures. 

   The aborted test run from last weekend provides a 'map' of PDif 
problems from X, Ku, K, Ka, and Q bands.  Here is a summary of antennas 
with zero-mean PDifs:

   X-Band: 
              ea02 -- all IFs
              ea12 on IF 'D'
              ea27 -- on all IFs

   Ku-Band:
              ea27 -- on all IFs

   K-Band:
             ea23 -- on all IFs
             ea27 -- on all IFs

   Ka-Band:
             all are switching

   Q-Band:
            ea08 -- on all IFs.