[evlatests] Spurious sources at X-band too.

[Vivek Dhawan]

On a tip from Joan I looked at Edo Berger's data from S8531, Apr 20th.
About 9 hours of data, standard X-band continuum setting.

He used fast switching with only 45s on calibrator. For reasons I have
not explored fully, the EVLA antennas often had no fringes on the short
scans (Perhaps to do with 5s dump time and the scan times not being
aligned with the switch cycle?) The VLA antennas fringe consistently
for ~35s of each short scan.

Enough data survived on EVLA-EVLA baselines to show a spurious 10-15mJy
source near the phase center, stretched westward (the beam is nearly
circular). All 4 IFs show the fake source. All corresponding images
with VLA-VLA baselines show a field with no obvious artifacts and
only 0.2mJy at the center. Plots are attached. All 4 IF's are similar.

I have informed Edo.

I have a test running later today at C, K and X band.

What else do we do now? I am cherry-picking people's data (or asking
them to look carefully, if they are locals) to see if we can identify
a start time for this bug.

I still don't know if the VLA is completely immune.

Vivek.
-------------- next part --------------
A non-text attachment was scrubbed...
Name: VV1.PS
Type: application/postscript
Size: 4059341 bytes
Desc: not available
URL: <http://listmgr.nrao.edu/pipermail/evlatests/attachments/20070424/cf39fc03/attachment.ai>
-------------- next part --------------
A non-text attachment was scrubbed...
Name: EE1.PS
Type: application/postscript
Size: 4059341 bytes
Desc: not available
URL: <http://listmgr.nrao.edu/pipermail/evlatests/attachments/20070424/cf39fc03/attachment-0001.ai>