[evlatests] Tests on September 22, 2005

[Ken Sowinski]

                              EVLA Tests
                          September 22, 2005

Lots of little things were fixed by Jerry in the first couple of
hours.  The most significant was connecting the right synthesizers
to the B and C downconverters in antenna 14.  Jerry verified that
16 is in sync in the sense that noise tube transitions are 
synchronous with the VLA; but it is still true that the NT is out 
of phase and the T5 SD voltages are negative.  This is not a problem
for the Modcomps since they use the magnitude of the SD voltage.
The L302-1 in 16 did not lock when I went to C band and required being
rebooted to work again.  After that it behaved for the rest of the day.

Rick and Bob spent a few hours at antenna 14 before they were chased 
off by bad weather.  In that time I looked at 16 again using 50 MHz
continuum observations with the T_sys correction turned off.  Delays 
had changed for IF A at all bands; probably because of the antenna being
re-synced after the L305 work on Wednesday.  Pointing was tuned a
little more at K band.  It still seems that 16 is a good antenna at 
K band.  Its response is about 1.5 while VLA antennas were around 2.5.
To assess stability 3C273 was tracked from 21 08 10 IAT to 21 29 00.

By now antenna 14 was available.  It also works reasonably at K band,
but IF B seems to be about 40 percent worse than the other three.
I started going through the bands systematically comparing 14 with 16
until the ACU MIB in 14 stopped responding.  Given the limited testing
all I can say is that 14 and 16 are comparable at L and X band; but 
14 is 2 to 3 times better than 16 at C band.  Even so, 14 is not nearly
as good as VLA antennas at C band and more work is necessary to find 
out why.

The ACU MIB has been misbehaving for several days now.  It was first
noticed on Tuesday when Rick and Bob were at the antenna.  It happened
briefly this morning, but recovered, and it died permanently about 1630
this afternoon.  The antenna autostowed after a little while and the
E-stop has been set.