[evlatests] Antennas 21 and 24, X-band

[Rick Perley]

    We had a few minutes at the end of software time yesterday to check 
EVLA functionality at X-band. 

    Antenna 21 gave no fringes on any IF.  The reported backend Tsys 
values are quite outrageous:  75, 560, 105, 105 K on IFs A, B, C, and D, 
respectively. 

    Antenna 24 works fine on IFs A and C, but is dead on B and D.  The 
cause is, I believe, known.  The good data seen on A and C is at 
variance with last week's results, where 24 B and C (at least) showed 
multiple levels of amplitude.  This problem now seems to have vanished. 

    Antenna 14C works fine at X-band.  Other data taken yesterday showed 
a two-phase state for this antenna-IF -- separated by 150 degrees, but 
only at P and L bands.  The data are typically in one phase state for a 
few seconds, then switches to the other state.  The switchover time is 
on the scale of one second, as we get intermediate phases and reduced 
amplitudes for one or two integration periods (0.41 seconds).