VLA Test/Observation Coordination Meeting
                           B.G. Clark
                        August 21, 2003


1.  eVLA

Antenna 13 has come out of the Assembly Building, and is now sitting
on the master pad.  It is largely an empty shell at the moment, but
outfitting work is proceeding.  P. Napier showed pictures, with at
least one feed inserted into the new feed cone structure.  Installation
of the optical fiber cables on the antenna has been done, and some
of the new electronics racks will be installed shortly.  It is 
expected to have a (sort of) functioning receiver installed within
one to two weeks.  Astronomical source tracking, and first fringes
are expected early next year.

G. Taylor notes that antenna 15 is now in the assembly building, and
the VLA is now a 26 element array for a significant time.  Antenna 
15 was at a somewhat unfortunate location, E8.  Having it missing causes
calibration difficulties in the current A configuration because it 
greatly reduces the number of short spacings.  It has been the habit
of observers at X-Band and lower to simply assume that the fundamental
calibrators, 3C 286 and 3C 48, are unresolved on the shortest baselines.
With a reduced number of short baselines, one should use a source model
instead, and we are well setup neither to supply a canned model nor
to get the word to observers on how to calibrate better.

2.  Beam Polarization

R. Perley reported that previous measurements at 20cm of the beam
polarization effects were exceedingly tedious to make, and something
more efficient was required to explore the discrepancies with the 
GRASP calculations done by W. Brisken.  T. Cornwell has implemented
getting data taken in holography mode into a form where it can be 
conveniently examined.  Holography data is available for all bands
already, so things can be examined easily.  The results are puzzling.
At all bands, the U Stokes parameter looks about as expected, with 
the cloverleaf pattern expected from the radial polarization expected
from geometric effects projected onto the U direction.  The Q parameter,
however, is swamped by a large gradient across the beam in the horizontal
direction.  This behavior occurs at C and X band as well as at L band.
It is suspected that this is somehow related to the fact that the
holography was done with the holographic scanning done vertically.
The mechanism of the effect is far from clear at this time and a software 
error cannot yet be excluded.

3.  4 meters with PT

R. Perley says that a problem with mislocated dipoles was fixed just in
time, and excellent images are now being made.  An image of Cas A 
was made by T. DeLaney with little trouble (resolution 8" with a round
beam), and R. Laing appears to have a good image of the relatively faint 
source 3C 31 (only 70 Jy, with the much stronger 3C 48 in the antenna beam).

4.  K and Q band receivers

Y. Pihlstrom measured the system temperature across the band for K and
Q band.  At K band, system temperature is pretty flat.  The main effect
is that not all LO systems will remain locked at all frequencies.  Most
work to cover the 21-25 GHz band, and many antennas work from 20.5 to 
25.6 GHz.

At Q band, there is much more variety in LO behavior.  Some antennas
will not tune below about 42 GHz while others will work down to 38 GHz.
In this band, the oxygen absorption band significantly raises the system
temperature above 47 GHz.

Results for both bands can be viewed at 
http://www.vla.nrao.edu/astro/guides/highfreq