[evlatests] BD Tuning Troubles ...

[Rick Perley]

    A short test was run on 3C84 at K, Ka and Q bands to test the 
hypothesis that a failure to invoke 'set and remember' caused the 
dramatic loss in amplitude on many BD IFs in my Cyg A experiment, run 
last night. 

    The hypothesis is confirmed.  Setting and holding the attenuators at 
an appropriate level provide appropriate cross-power amplitudes. 
   
    But the test has revealed some other curiosities with the BD IFs:

    In all three bands, antennas 22 and 25 failed to fringe in IF 'D', 
but operated normally in the other IFs

    For K and Q bands, antenna 13 failed to fringe in IF 'B', but worked 
well in IF 'D'.  (This antenna has no receiver in Ka band).
    For K and Q bands, antennas 14 and 16 failed to fringe in both IF 
'B' and 'D'.  (These antennas have no receivers at Ka band). 

    Are these expected behaviors?