[evlatests] State of EVLA, Jan24 / not good!

[Vivek Dhawan]

After their EDFA bypass operation, EVLA antennas were put to work in
AL730. I looked at a stretch of data starting last night and found some
far-out antennas working OK (see disclaimer below); some close-in ones
working poorly, and most working on 2-3 out of 4 IFs. I could not see
an obvious pattern with distance or arm location.

In sum, I think the data from most of the recovered EVLA will be a
headache to examine and calibrate for AL730, but their analysis of
source variability is probably the best way to get feedback on this.

The use for other projects seems doubtful. I guess we should await the
stress tests that will be run after AL730 and see what Emmanuel has to
say.

-------------------

Gory details:

The assessment was a simple glance over the amplitudes on strong
sources, of which many are being observed in AL730. In many cases it
was obvious there were short-term amplitude variations (timescale of
seconds) and 10's of percent. There is a reduction in mean amplitude
but the most obvious thing is the scatter.

There were intermediate states with less variation, and the badness
seemed to vary through the night. Even without obvious variation,
there may still be low-level corruption of data. This was no more
than a quick look.

Phase variations accompany the amplitude variation, plus poor weather
did its thing, so the best quick check is on the amplitudes.  I should
probably load a bit of data with the Tsys not applied and see if there
is any difference - more later.

The list. EVLA antennas 13, 23, 26 not observing

All 4 IFs appear good on: ea2, 9, 21, 24, 28.

3 out of 4 IFs good (bad IF in brackets) on
ea1(2R), 4(1L), 14(2R), 16(2L), 19(2R), 25(2R).

2 out of 4 IFs good (bad ones in brackets) on
ea5(1L 2R), 11(1R 1L), 17(1R 1L), 18(1R 1L).

0 out of 4 good: ea03 all 4 IFs variable.

--------------------

LOCATIONS: (*=EVLA antenna)

File=AL730-1     .X BAND.   1
Array= VLA          Freq=  8435.100000 MHz     Ref.date= 24-JAN-2009

                                N72 ( 7)
                                N56 (27)
                                N40 (12)
                                N32 (20)
                                N24 (25)*
                           *(19) W4       (  )
                          ( 6) W8       E8  (10)
                        (  )              E12 ( 5)*
                     *( 1) W16                  (  )
                    (  )                      E28 (14)*
                  (22) W36                          (  )




File=AL730-2     .C BAND.   1
Array= VLA          Freq=  6585.100000 MHz     Ref.date= 24-JAN-2009

                                N16 (18)*
                                N8  (28)*
                            (  )      E4  (11)*
                         *(17) W12          (  )
                        (  )              E16 ( 3)*
                     *(16) W20              E20 ( 2)*
                    (  )                      E24 ( 9)*
                 *( 4) W28                          (  )
               *(24) W32                          E32 (21)*

-------------------------