[evlatests] Oct 20 Cband: Phase transfer

[Ed Fomalont]

Some initial results from the C-band data taken on Oct 20

Observation summary:
   2.6 hours, 12 telescopes, 5 sources,
   four sub-bands, 4.6 -> 5.0 GHz

Main reference source:  1310+323
Other sources: 1326+319, 1331+305, 1330+251, 1327+221

Major problem:

   Telescope 8, pol L has a sinusoidal bandpass response with a period of
   63+/-2 MHz.  It is like the true bandpass is rotated in phase with a
   revolution every 63 MHz.

   Other telescopes have reasonable sensitivity.

Angular stretching of Sources:

   The angular stretching of source positions away from the direction
of the phase reference location is now very small

Band    Date   Frequency Range       Stretching factor
C     Sep 27   4.63 - 5.00           7.8^(-5) ± 0.3
C     Oct 19   4.63 - 5.00           0.5^(-5) ± 0.3

It is a more than a factor of 10 less than the C-band observations of
Sep 27, and whatever remains could be caused by other effects such as
the lack of round-trip phase or remaining elevation dependence of the
phase.