[evlatests] Ea19, at L-band

[Rick Perley]

     Something is odd with ea19 at L-band.

     The system temperature, as measured by the PSum/PDif ratio claims 
to be about 150 K on 3C48.  However, the Tsys ratio between Cygnus A and 
3C48 is completely normal (4.82), so the sensitivity of the antenna is 
fine -- these Tsys values are bogus.

     This normally points to a bad value of Tcal.  But the value in the 
'CD' table is also completely normal -- 1.42K.

      So it's acting as if only about 1/4 of the switched noise power is 
actually getting into the signal path.  (And indeed, the PDif values are 
~ 17 millicounts -- at least a factor of four too low). In other words, 
the effective Tcal is about 0.35 K.

     Can anybody explain what is wrong?