VLA Test/Observation Coordination Meeting
                           B.G. Clark
                        January 15, 2004


1.  eVLA

S. Durand reports that the final version of the round-trip phase measurement 
equipment is now working.  The short term noise on the measurements is 
better than 0.1d at 512 MHz.  Equipment operating on two different fiber 
pairs (to antenna 13, on the master pad) appear to track each other well.
The digital transmission system system is close to working.  It has been
run in the lab with four colors (48 Gbits/sec), and a demonstration of 
this on the antenna is planned shortly.

2.  Water Vapor Radiometers

C. Chandler has been analyzing data from the two WVRs installed on 
antennas.  The WVRs are connected to the output of the 1.3cm frontend,
and have three channels positioned at the peak and inflection points 
of the water line.  The method of use is to, for any given day, 
derive the proportionality between interferometer phase and the height
of the water line, and then using that constant of proportionality
to correct short term phase variations.  The coefficient of proportionality
determined experimentally is a factor of 1.5 to 2.0 greater than that
expected from theory, which is not understood, but is consonant with
what is seen by other WVR users.  In fact CC finds that fitting the
individual channel weights can result in a much improved result.
It is perhaps possible that in operational use the several minute
observation to determine the coefficients could be replaced by 
the normal calibrator observations, but for studies, and for initial
operations, this complication would be avoided.

In order to progress further on this project, more WVRs are needed.
CC recommends four, to be ready when we next go to A configuration
in September.  A MIMIC surface mount component design is underway.
Temperature stabilization is a difficult and critical component of
the design.