[evlatests] EVLA tests, Mar 23 2006

[Ken Sowinski]

                       EVLA Tests, March 23 2006

Today was mostly spent getting newly installed equipment to work.

As reported yesterday P band is now available in antenna 14.
Cables were swapped this morning and polarizations are now the
right way around and it more or less works.  Levels are set
to something that gives reasonable SD voltages and correlations
but the SD behavior with power is interesting and should be
looked at more carefully some time.  It is still true that
phases are winding in the BD IF pair.  It is not a continuous
wind, but a clunk every 10 seconds.  Today the rate is about 
80 degrees each time.  I suspect a broken L302, but wonder why
it seems to work for the other bands.  It more than likely is
a broken L302: I found in the last few minutes of test time that
K band is seen to suffer the same problem.  The default explanation
should be a broken L302.

The UX converter was installed in antenna 13 and both K band and
Q band are working well.  Delays have been set and a rought stab
nade at focus and pointing for Q band.  Walter was able to determine
attenuator settings and install them in the data base.  The only 
problem, common to both bands, is that the SD voltage for IF B 
is pegged at -10 volts.  In spite of this, there is correlated 
data for IF B.  

There are two segments of data that someone might want to examine.
1.  A long scan at K band including antenna 13 start4ing at 1905 IAT
and ending at 1954 IAT.
2.  A long scan at P band on 3C48 starting at 2210 and ending at 2236.
It would be interesting to look at the BD phases to see of the
magnitude of the phase clunk changes over time.

While getting antenna 13 to work at Q band Az collimation for 16
was adjusted so that it might now be a little better at Q band.