[evlatests] January 22-26 tests

[Steven Durand]

RE:	Digitized 512 MHz Comb Line Test


The week of January 22-26, the Electronics Division, with Ken’s help, 
would like to run a long series of tests to determine the source of the 
EVLA phase stability problem.  Antennas 18, 24, and 26 will be 
configured as a sub-array and multiple tests will be run throughout the 
week.

These three antennas will be modified to remove the front ends and 
up/down converters from the signal path.  The plan is to install an 
additional modified L300 and use the 512 MHz comb generator output to 
feed the anti-aliasing filter in the T304/5.  The DTS modules will 
digitize the tone and the signal will be correlated.  Performance of the 
L300 L304 and L305 will be determined using this configuration and we 
hope to determine if the phase stability problem is inside or outside 
the LO/IF rack.

The three antennas will start looking up and each in turn will be tipped 
and rotated.  Once a baseline is established a set of modules with 
semi-rigid coax cable will be installed in one antenna.

Since we plan to use the LO distribution system, the three antennas can 
be located anywhere in the array.  As a reminder the three antennas will 
NOT be usable for astronomy during this week and will go through the 
Electronics EVLA Acceptance test before returning to the array.

It is anticipated that the February 12-16 test time will still be 
required to complete this investigation.

-- 
Steven J. Durand                 National Radio Astronomy Observatory
Electronics Division             1003 Lopezville Road
505/835-7103                     Socorro, New Mexico  87801