[evlatests] Some Very Interesting Data ...

[Jim Jackson]

Ant 6B -  The T304 and a clock cable to the DTS module were both 
replaced/repaired in the last two weeks - apparently it is still not 
fixed. The removed T304 (s/n 56) showed no sign of this behavior on 
the bench in over a week of testing - there is a brand new one (s/n 
113) in the antenna now.   As this is in all bands,  does not seem to 
show up in the T304 TPD's and is obviously a very digital problem (2 
stable discrete states), the next step is to replace the DTS module 
followed (in order) by the deformatter and Widar station boards.

Ant 6D - Someone probably needs to look at formatter/deformatter 
alignment and/or rerun delays.  These issues will be addressed by the 
new DTS firmware to be deployed with the 3-bit digitizers.

Ant 11B - After we figure out 6B, we'll do the same thing to 11B.

Ant 3 - We thought this was fixed but apparently not.  This antenna 
keeps coming up with odd stability issues.  We may need to look 
closely at LO distribution, fiber, the L304/305/300 and maybe even 
the P301 power supplies on this antenna.

Ant17 BD - There have been recent occasional complaints about both IF 
pairs (at different times) on this antenna.  This may be related to 
issues with the L300. We'll look into it.

The Rest:  No immediate ideas.  We'll look into them as we have time.

Cheers,
Jim

At 12:26 PM 4/6/2010, Rick Perley wrote:
>     Michael took some C-band data yesterday evening, which has revealed
>some problems, some old, some new.
>
>     The dataset consists of a single strong point source, observed
>continuously for 30 minutes, but with a new scan every minute.  The goal
>was to see what (if anything) these new can commands did.   The
>frequencies used were 4800 (AC) and 7000 MHz (BD).  The usual 128 MHz
>BW, with 64 channels in all four polarization products for each subband.
>
>     Some general observations:
>
>     *  Antenna 13 has no receiver.
>     *  Antenna 28 gave no fringes on either subband at any time.
>     *  Antenna 23 was tardy getting on source.   If this is recurring
>behavior, servo should be notified.
>
>     Overall, data quality was simply outstanding!  But, (as always, eh?)
>there are some notable exceptions:
>
>     A)  Antenna 5 gave perfectly zero amplitudes in IF C, and a very
>strange spectral shape (rapid oscillations in frequency) in IF D.  The
>latter showed a delay of 136 nsec as well.  MPR says these were due to a
>formatter problem, which has been repaired.
>     B) Antenna 6D has a 40 nsec delay.  All other subbands show delays
>less than 5 nsec.
>     C) I generated bandpass functions for each antenna/IF/polarization
>for each 1 minute scan.  Perusal of these solutions should fabulous
>bandpass stability (changes << 1% from scan to scan), *except* for
>              2C:  turnups or turndowns of ~1% at lower edge,
>              6B: very large -- (10s of percent) -- turnups or turndowns
>at both edges edges, with poor stability in the central channels;
>              11B:  Same as 6B, but not as bad -- few percent.
>              17 has poor sensitivity in B and D -- this would be
>expected if there was an old-style polarizer in it, but according to the
>EVLA retrofit sheet, it's supposed to have been retrofitted.
>
>     D)  Antenna 5 drops amplitude by 15% on every 1-minute scan change,
>on all IFs.  No other antenna showed this.
>     E)  Antenna 6Bchanges amplitude by ~ 6% every 57.6 seconds.
>NB!!!!:  This behavior is *not* connected to the 1-minute scan changes.
>The nature of the two amplitude states is curious:  The higher state is
>relatively
>stable -- every other transition comes to the same level.  The other
>(lower) state is variable in amplitude -- and within the 57 seconds
>spent in that state, the amplitude usually (but not always) is changing.
>     F)  Major-League Wobbles are found!!!  Baseline 6 x 11, IF 'B' only,
>has a 25% sinusoidal amplitude oscillation, with two periods clearly
>visible to the eye:  116 seconds and 12.5 minutes.  Baseline 11 x 25,
>also IF 'B', has a much weaker wobble, 7% amplitude (pk-pk), with 129
>second period.  There is *no phase* oscillations seen on either
>baseline.  There could be more wobbles out there -- I haven't looked at
>all baselines on all IFs.  If there are, they can't be as large as the
>ones I found (which were large enough to show up in CALIB solutions).
>     G) Antenna 3, all IFs shows some odd amplitude/phase drops and
>changes, of small (few percent) amplitude, of which there is no easy
>description.
>     H) Antenna 20D shows a faint amplitude oscillation 0.5%) of ~4
>minute period, which does not appear to be due to baseline-dependent
>wobblese.
>     I) Antenna 5A shows two phase states, separated by 60 degrees.
>There were 13 phase jumps, *each of which* exactly coincided with a scan
>boundary.
>
>
>     E) An
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