[evlatests] A mysterious effect in ea26, at X-band.

[Rick Perley]

    Vivek and I have noted a most bizarre problem with antenna 26 -- 
only at X-band. 

    As a function of elevation we find that the Tsys *declines* at the 
elevation decreases, while the observed fringe amplitudes *increase* as 
the elevation decreases.  Both of these are exactly reversed from normal 
behavior.   Tsys values are very high in general. 

    Meanwhile, the PDif values inform us that system gains are not 
changing. 
   
    Interpretation:  The antenna acts as if we have absorber in front 
of, or within, the feed, whose absorption varies with elevation. 

    The most likely culprit is water in the feed.  Can somebody go take 
a look at the X-band feed on ea26?