[evlatests] total power measurements and antenna 16

[Ken Sowinski]

I was at the VLA today to take care of a Modcomp problem and
took advantage of that to measure the deflection in TP due
to 3C273 for the two EVLA antennas at all bands.

General comments.  I turned off the backend ALC at the T5 and
tried to measure TP on and off 3C273.  Except at K band the
deflections were large and it was easy to get a five to ten
percent result.  14 did not seem to be very stable at X band.
In general 14D was behaving funny: I can easily see the sudden
jumps that Rick and Bob reported seing at the downconverter
output.  The SD voltage is still negative for antenna 16.  The
ACU in antenna 14 behaved impeccably.

I express the deflection as (on-off)/off averaged over IFs and
in some cases over two trials; the error is an eyeball RMS of
the deflection estimated from the variation amon IFs.  No idea
why the result is so large for L band.
Antenna    14                 16
L   0.39  +/- 0.04      0.31  +/- 0.06
C   0.11  +/- 0.003     0.026 +/- 0.002
X   0.082 +/- 0.07      0.10  +/- 0.003
K   too unreliable to report

This is consistent with my report of interferometrically derived G/T 
for antenna 16 at all bands on Sept 20.  At that time C band was 
about 1/4th as good as X band.  I leave it to someone else to look
up the flux of 3C273 and say what these numbers mean in an absolute
sense.

This rules out LO purity and alisasing to explain the poor performance
at C band.  The only likely suspects are pointing, antenna optics, and
system temperature.  If we were pointed at a sidelobe power would be down
by at least 10 dB; we only see about 6 dB compared to X band.  An optics
problem would probably be seen in beam cuts; we should try this next week.
Unlike the other receivers the C band cryo temperatures are not monitored
There is a readout on the side of the receiver which I am told indicates
cryo temperature.  I am told that it has been reading 5.51 lately, but
I have no idea what that means.

The two things to do next week are to measure system temperature and
try beam cuts.  We have enough test time that it should be easy to find
time for the latter.