[evlatests] C-Band Sensitivity (Good News)

[Rick Perley]

    The C-band results from this weekend's run give confidence! 
Unfortunately, antennna 13 was not operational at C-band, so
we have only 14 and 16. 

    From the spectral line data, we find:

    1) No closure errors to the 1% level (about where the noise lies). 

    2) No funny dropouts in amplitude or phase or any kind. 

    3) Sensitivity: 

           IF 'A'.  From the aipsweights, we see that antennas 14 and 16
are the most sensitive of all.   However, their 'aipsweights' (proportional
to efficiency/Tsys) are only slightly better than the best VLA antennas,
and about a factor of 2 better than the worst VLA antennas at this band.

          IF 'B'.  Here we find antennas 14 and 16 *far and away* better
than the best VLA antennas -- by a factor of 25% over the best, and
by a factor of 2.5 over the worst.  This is exactly the ratio we've been
looking for! 

    IF 'C'.   Antenna 14 is the best of all, but antenna 16 is only 'run of
the mill'.  Ken reports the same for 16C and 16D from his corrrelation
coefficient measures.  We deduce there is something wrong with that
(LCP) receiver, although the reported Tsys values look fine. 

    IF `D' was not reviewed at report time.  (Perhaps later today). 

    Discussion:

    Readers of my L-band report should remember my noting that
antennas 13 14 and 16 had rather poor sensitivity in IF 'A', while
having normal (expected) values in IF 'B'.  This is the same pattern
seen here at C-band.   It is suggested that IF `B' represents proper
overall sensitivity behavior, while some channel-dependent effect
(say, in the T304s or the T4s, or some power level setting, or within
the D-A converters) is degrading IF channel `A'. 

   I will check X-band performance shortly.