[evlatests] Q-band holography d.d. 2011-10-29

[Michiel Brentjens]

** [2011-10-31 Mon 12:11] Q-band holography d.d. 2011-10-29

Temperature sensitive gains?
----------------------------

A 3C273 Q-band holography observation from past Saturday shows a
systematic decrease of PDIF over the course of six hours in virtually
all antennas. This *decrease* in accompanied by a similar slow,
systematic *decrease* in visibility amplitude. Typically, PDIF
decreases by 20%. The visibility amplitudes also show a 20% decrease,
although they are much noisier than the PDIFs.

The source had a fairly constant elevation between 36 and 57
degrees. The observation began at 08:00 MDT and ended at 14:00
MDT. Are we seeing a temperature dependent Q-band gain here? Notable
exception is IF 3C, which shows nicely constant PDIFs, yet also
decreases its amplitudes along with all others.


Other phenomena
---------------

For some reason, 11R lost all signal around 16:50 UTC. After 17:30
UTC, the PDIFs of 20L become increasingly more noisy, until they
suddenly snap together at a higher value around 19:05 UTC. 12A PDIFs
are consistent with noise. 4L PDIFs behave nicely until 17:00, at
which point they increase by 50% and begin behaving erratically.

- Michiel