[evlatests] Short, Shallow Dropouts

[Rick Perley]

      A test was run at noon today to determine if Walsh switching is 
the origin of the short dropouts we occasionally see.

    In review, most EVLA antennas show occasional (much less than 1% of 
the time) shallow (less than 10% in amplitude) drops when we dump at 
0.416 second rates.  The opposite polarizations always drop together and 
by identical amounts.  There is no correlation in drop times or 
frequency between the two different IFs. 

    The test ran for 30 minutes on 3C84 with Walsh switching on, then 30 
minutes with it turned off. 

    Result:

    No change in drop behavior or statistics.  The antenna which dropped 
the most today (antenna 24) did so equally before and after the 
switching was turned off.