[evlatests] Antenna 16 Phases, Line Data

[Rick Perley]

    As noted in the previous message, observations of 3C48 and 3C84 were
made in line mode as well.  I've reviewed the amplitude and phase behavior,
and there are important differences from the continuum.

    For 3C48, the phases were stable within each scan -- no 'spinning'.  
This
is the same as in the continuum data. 

    For 3C84, four scans had stable phases, 3 had spinning phases.  For the
spinning phase scans, the phase rate *started at zero* and continually
increased throughout the scan.   The increase was positive for the first
spinning scan, negative in the 2nd, and positive for the last spinning
scan (which was the 5th scan overall).  The important difference between
this behavior and that for the continuum data -- which never had a zero
phase rate -- is likely connected to the observation methodology:  The
spectral line 3C84 scan followed the continuum one, so the antennas
were already on source.  The continuum 3C84 scan followed a spectral
line 3C48 scan, so there was about two minutes of slewing.  The zero
rate (if there ever was one) was not seen as the antennas were not on
source. 

    The maximum phase rate seen in the spectral line data is about
50 degrees *per integration* -- the same as the continuum, *if we
ignore the length of the integration*.   (In real units, the rate maximizes
at about 15 degrees/second, or 1/8 the continuum rate). 

    There is no loss of coherence associated with the phase wind -- the
same as inthe continuum. 

    The amplitude reductions are only seen in those 3C84 scans
with the spinning phases!  This is the same behavior as observed in
the continuum data set.  I no longer believe this is coincidental, but
am at a loss to explain why the 3C48 data has dropouts, but no
spinning phases. 

    I believe the above strengthens the case that the effect is generated
by the Modcomps, rather than at the antennas (which know nothing
about the correlator integration time).