VLA Test/Observation Coordination Meeting B.G. Clark October 16, 2003 1. eVLA Antenna 13 first light at 3.6cm is expected in early November. The 327 MHz feed could be connected up later in the month. The 21cm feed is under construction at the site. It is expected to be finished in December. 2. System linearity R. Perley made a first cut at determining the effects of compression, using the existing VLA system. Observing at 3.6cm, he looked at 3C 84 and turned on the solar cal signal, which provides about 13 dB increase in system noise above the cold sky. This is still believed to be well within the linear response range of the system, however. In any event, there was no discernible effect on closure errors, whose RMS was 0.3% in amplitude and 0.1d in phase. He plans to pursue further tests by injecting a CW signal strong enough to saturate the front end amplifier, but lying outside the observing band. 3. Polarization beams Further report by R. Perley of work by T. Cornwell. With proper calibration of R-L phase, the polarization appears generally radial, as it should, at L and X bands. The v Stokes beam patterns are the gradient perpendicular to the feed offset, as expected (the well known "beam squint"). The C band patterns, however, do not appear to correspond to expectations. Polarization is horizontal on one side of the beam and vertical on the other. (The feed offset is approximately in the vertical direction.) So the vertical and horizontal polarization beams appear to have a squint, in the same direction, and of somewhat greater magnitude, than the R-L beam squint. The effect is unexpected and not understood.