[evlatests] Bz for antenna 24, revisited

[Rick Perley]

    Oops!  My previous estimate for the Bz error of antenna 24 was 
spectacularly wrong, for two reasons:

    a) Inspection of  a closer pair of calibrators (separated by only 
2.0 degrees) gives a ~45 degree (constant) phase difference at 1275 Mhz 
(and  ~60 degrees at 1675 MHz).  Hence, there is at least one full turn 
of phase left out of the previous estimate. 
    b) I left out a 'Delta Dec' factor. 

    With these new numbers (and the proper calculation), I get a Bz 
error of a remarkable 7 wavelengths at 1675 MHz, or about 1.3 *meters*. 
It could be more, if there's another turn of phase missing. 
    There is no sign of the sinusoidal phase reflecting a Bx, By error, 
so this error has got to be some sort of database entry problem.