[evlatests] Thurs evening instr. pol run

[George Moellenbrock]

Hi All-

Had an L-band instr. pol run last (Thurs) evening, mode PA, 12.5 MHz, 
tuned serially every 60s to cover 1300-1550 MHZ.  EVLA participation was a 
bit spotty (its been a tough week, alas):

14:  Looks good.
16:  Locked out (?), did not participate.
13:  Joined after Herculean efforts of Rob, Jim, Ken, and others over
      last day or so (Thanks!).  Amplitude level (3C84) about as expected
      (at most a few 10s % weak) for first ~40 minutes, then it dropped
      (instantaneously) by an order of magnitude and stayed that way for
      the rest of the observation (though still clearly coherent).  Fringe-rate
      (to ant 11, next ant inward) consistently about ~1 mHz, uncorrelated
      with amplitude states.  Ken suspicous of pointing to explain
      amplitude problems (but at L-band?!).  One of the 20 tunings (band
      center at ~1419 MHz) appears to have apparently failed to
      lock---there is no correlated signal there.

Though there is little to learn about EVLA-EVLA instr. pol in this 
observation (early 14-13 may be ok), I observed a strongly polarized 
source, which I hope to use to register the freq-dep R-L phase, and apply 
to my observations over the past few weeks.  With some luck, I hope this 
will improve the prospects for a fully complex (A+P) comparison of 
astronomically-determined instr pol with Bob's lab measurements of the 
EVLA polarizers.  (The amplitude comparison already looks pretty good.)

-George