[evlatests] AR603 21aug06 X band

[Michael Rupen]

Here I report antenna sensitivities from AR603 yesterday at X band, because
a couple people wanted to know about ant. 18 ASAP.  I fear it's very noisy
indeed, Tsys~ 100-150 K and sensitivity (by AIPS weight) 20x worse than the
rest of the array, in all IFs.

AR603 21aug06  07:43-08:43 IAT
------------------------------
mrupen 22aug06

EVLA ant. 13,14,16,18 included

Dynamic run

Standard continuum, C X bands, one fast switching and two "regular" scans
   in each band
3.3s averaging
elevation 23-63 degrees (mostly 23-30 degrees)
Fine weather (60% clouds, API 4 degrees)

ODDITIES
   On-line flagging seems to have worked _almost_ perfectly for the EVLA.
     The one flaw occurs during fast switching scans.  The very first source
     is fine; but, at every source change within the fast-switching scan,
     the EVLA antennas appear first (and obviously off-source) for 2 records;
     then everyone vanishes for 10 seconds; then both VLA and EVLA antennas
     start appearing, on-source, and indistinguisable from one another.
     The same signature is seen in both bands.

OVERVIEW
  Comparisons are with similar data from 11aug06.

   6cm:

   4cm:
     ant. 13
       IF A much improved -- now among the best!
       IF C remains OK (10th of 26)
       IF B has gone downhill -- it's now among the worst
       IF D remains among the worst
     ant. 14 is basically the same -- ok but not outstanding in AC,
       lousy in BD
     ant. 16 remains superb, among the top antennas
     ant. 18 is by far the worst in the array
       Tsys is 100-150 K, vs. 30-40 K for the others

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

AIPS weights: median ranking, out of a nominal
   26 antennas
   --> 1 is the best; 26 is the worst <--

          6cm   4cm
   13-A          2
   13-C         10
   13-B         25
   13-D         23

   14-A         12
   14-C         23
   14-B         15
   14-D         22

   16-A          4
   16-C          3
   16-B          4
   16-D          3

   18-A         26
   18-C         26
   18-B         26
   18-D         26

   ---- ==> no data
   n.f. ==> no fringes (low amp, random phase)

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

AIPS weights: median fractional weight
   mean weight is calculated for each record
   fractional weight is the weight for the EVLA antenna,
     divided by that mean
   the median fractional weight is the median value of the
     fractional weights, derived from the distribution across
     all records in which the antenna was present
   --> high is good <---
   --> the average VLA antenna is 1.0 <--
   --> 0.1 is 10 times worse than the average;
      10.0 is 10 times better <--

          6cm   4cm
   13-A         1.37
   13-C         1.10
   13-B         0.43
   13-D         0.62

   14-A         1.04
   14-C         0.76
   14-B         0.97
   14-D         0.71

   16-A         1.20
   16-C         1.25
   16-B         1.20
   16-D         1.26

   18-A         0.05
   18-C         0.05
   18-B         0.05
   18-D         0.03

   ---- ==> no data
   n.f. ==> no fringes (low amp, random phase)

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