VLA Test/Observation Coordination Meeting
                           B.G. Clark
                         March 17, 2005


1.  Efficiencies

R. Perley has been doing single antenna measurements of efficiency
on VLA antennas to compare with what he has been doing on the EVLA
antennas.  At 1.3cm, he measured antenna six, finding that the 
feed spillover increases the system temperature beyond the atmospheric
contribution, starting to be significant at about the 15d to 20d
elevation level.

At L band he measureed the effect of the 4m dipole using this technique.
Putting the dipole up causes about a 2.6% loss in efficiency and an
added system temperature of about 1.8K, roughly agreeing with previous
measurements which estimated a 10% loss in G/T.

This is the first absolute measurement of the 90cm system.  RP ued
a hot/cold load system, with a load replacing the feed, which may 
introduce a little uncertainty in not including the feed match.  He 
measures a receiver temperature of 110 K (somewhat worse than expected
but still less than the zenith sky, which was at about 230K),
and an efficiency of 34%.

2.  196 MHz System

R. Perley, reporting on behalf of the CfA collaborators and C. Carilli
reported initial results.  There is a lot of interference in this band.
This is not unexpected.  Usually TV signals have most of their power
in the carriers, and the expectation was to be able to work in the
video and chroma areas between the carriers.  An unexpected discovery
was a digital TV signal in channel 9.  This is a UNM station operating
on Sandia Crest with 200 W broadcast power, which was swamping a good
deal of the band necessary for the EOR measurement they are hoping to
do.

Measurements could be made in a narrow band (2 MHz) channel.  They
could see Cas A, and could measure an efficiency of order 50% (but
very uncertain - it's still early days, and a lot of things aren't 
working right yet).