[evlatests] VLA Tests -- December Meeting Agenda

[Rick Perley]

     The December meeting of the VLA Tests meeting will take place 
tomorrow (13Dec), 10AM, Rm 317.

     I have four topics:

     1)  Referenced Pointing Troubles:  We get into real trouble when 
antennas arrive on source after the pointing raster has begun.  Only 
'new-ACU' antennas numbered 18 and higher are seriously affected.  I'll 
show the curious phenomena that result.

     2) Subreflector motion troubles.   Various failures in either 
rotation or focus, most notably connected with moving from Q to X band.  
This was from a science run.

     3) Band Switch Test.  A demanding test was run early last month, 
involving all 28 Cassegrain band combinations.  The results are 
generally good, but the expected troubles originating from the T303 
switches are certainly present.  Curiously, the subreflector motion 
issues noted above appear to be absent.  The major goal -- to see if 
ea10 has been cured, was met.  (It was).  The question is now:  Should 
another test be done before we press for a complete replacement of the 
identified switches?

     An ancillary benefit of this test was an accurate determination of 
the maximum and minimum times needed to change bands.

     4) Switched Power.  The Band Switch Test provided good data on the 
effectiveness of the switched power.  For 8-bit, the results are clear 
-- we should be utilizing these data.  For 3-bit, the situation is less 
clear, and some tests will be suggested.

     Josh Marvil will also have some data on the effectiveness of 
applying the switched power.