[evlatests] Apparent sensitivity changes problem found and resolved

[Rick Perley]

    I reported last week on a curious problem whereby X-band 
observations seem to increase in amplitude in some circumstances, in a 
way which was incompatible with any explanation involving antenna motions. 
    The problem was now been found and resolved.  It was due to an 
incorrect calculation by the data filling program of atmospheric 
opacity.  An off-line recalculation removes the problem.  The bug in the 
on-line filling program has been found and squashed.