[evlatests] Next 3-bit test results ...(no clarity yet ...)

[Rick Perley]

    As part of a plan to diagnose our problems with the 3-bit path, Ken 
adjusted the requantizer gains this morning (his message below).  I've 
quickly analyzed the results:

    1) Antenna 27 did not fringe throughout this test. 
    2) The delays on the LCP side changed dramatically (for the better!).  
          Yesterday they were:  0,-149,-79,250 nsec  (antennas 15, 22 27 28)
          Today they are:           0, 22, xx, 31 nsec.  (xx == antenna 
27 not fringing). 
       Ken says he did nothing to change the delays ...
    3) Bandpasses and phase stability look fine. 
    4) Amplitude stability is 'o.k.', but we still are seeing few 
percent changes over timescale of minutes that I don't think should be 
there.
    5) Sensitivities are as before -- RCP higher than LCP, both sides 
higher than they should be.  The expected answer is about 160 mJy.  What 
we have now is:

       15          22            28
        -----------------------------
15 |    xx         280         200
22 |   180        xx           260
28 |   190        180           xx


    More testing is underway as I write this.  Stand by for results ...

-------- Original Message --------
Subject: 	first installment
Date: 	Fri, 3 Sep 2010 12:01:56 -0600 (MDT)
From: 	Ken Sowinski <ksowinsk at aoc.nrao.edu>
To: 	Vivek Dhawan <vdhawan at aoc.nrao.edu>, Rick Perley 
<rperley at aoc.nrao.edu>



Here is the first bit of data.  The change over the last test is
that the requantizer gain has been set to produce the optimal RMS
of 2.7.

The script was begun at 1702 and ended at 1754; began with 3C147
and switched to 3C286 around 1745.  I finished adjusting gains
at about 1724.  I fiddled with the delay module for ea28-C at
about 1744.

The name was C3noise.

There will be more after lunch.  I am beginning to suspect a
timing problem for the IF C path in the station boards.

Ken