[evlatests] Further spectral line tests

[Claire Chandler]

Report on spectral line tests observed without Doppler tracking, from
Friday Jan 06, 2006.

These tests follow those from Dec 30, to check that spectral lines
are detectable on VLA-EVLA baselines when observed with fixed
frequency (no Doppler tracking).  The tests comprised:

1) Observations of a strong astronomical SiO maser at 43.1 GHz using 2
min scans

2) Observations of a strong OH maser at 1665 and 1667 MHz, 2 min scans

3) Observations of a strong H2O Maser at 22.2 GHz, 2 min scans

Mode 2AD was used, so no check has been made of IFs B and C for the EVLA
antennas has been done yet.

Results:

o Fringes were observed on all baselines, including VLA-VLA, VLA-EVLA,
   and EVLA-EVLA, at all frequencies.

o As previously reported by Rick, the sensitivity of antenna 16 is very
   poor at Q-band.  It is worse than the median VLA antenna by a factor
   of 3, so if the data from this antenna were weighted properly they
   would contribute almost nothing to an image.  This is most likely
   due to poor pointing, and the only reason I detected fringes on this
   antenna was because the SiO masers were so strong.

o The sensitivity of antenna 14 at Q-band is 10% worse than the median
   VLA antenna.  It is by no means the worst in these observations,
   however, which disagrees with Rick's earlier results and again suggests
   that pointing is probably a problem.

o The sensitivity of antenna 16 at K-band is worse than the median
   VLA antenna by a factor of 2.

o The sensitivity of antenna 14 at K-band is worse than the median
   VLA antenna by about 20%, and in these observations was the second
   worst after antenna 16.

o Sensitivities at L-band have yet to be analyzed, due to significant
   RFI on the VLA antennas.

Until referenced pointing is available it will not be possible to assess
properly the performance of the EVLA antennas at K and Q band.

Claire