[evlatests] more tests, May 30 2006

[Walter Brisken]

Oh my, what a zoo of issues I've found.

I did the 400 ms test (this time with no calcodes so no unrecorded data) 
at LCXK bands.  See responses to Ken's email about the "fixed" L302s in 13 
at the end of this message.  It appears that in addition to some things 
that look like real problems there were additional problems running the 
script.  Only the last 16 minutes of the 1 hour test got filled.  Appears 
to be related to a problem with the modcomps or DAT drives.  This was 
enough data though to see each of the bands, but not more than once each. 
Here's the scoop:

Double Dropouts
~~~~~~~~~~~~~~~
Antenna 18BD has "double dropouts" where two consecutive 400 ms 
integrations show reduced amplitude.  The first one is reduced to ~1/3 
nominal value and the second one is ~2/3 nominal.  Likely related to this 
are ~105 degree phase jumps every _5_ seconds; alternate 5 second periods 
are at 0 and 105 degrees from nominal.  The ~1/3 amplitude dropouts happen 
3 10 second ticks in a row, then skip several 10 second ticks, come back 
for 3 more, ...  The 2/3 amplitude samples are always dropped out.

UVPRT shows this for one such double dropout:

     Time       Ant    U(Kilo )   V(Kilo )   W(Kilo )   Amp  Phas  Wt
  0/23:21:50.8 15-18       5.84      -3.37      -7.76   1.726 -31 7280.1
  0/23:21:51.3 15-18       5.84      -3.37      -7.76   0.439 -30 7192.1
  0/23:21:51.7 15-18       5.84      -3.37      -7.76   1.115-135 7192.1
  0/23:21:52.1 15-18       5.84      -3.37      -7.76   1.742-134 7187.3

Note location of phase jump.  Why is this occuring after the 10sec tick by 
2 or 3 integrations?


On Tue, 30 May 2006, Ken Sowinski wrote:

> The major result today is that the L302 firmware fix to
> address the once every ten second amplitude glitch seems
> to work.  I can see no problem in either IF pair in antenna
> 13 after the modules were installed.  There will be a more
> careful observation this afternoon at all bands with short
> integration times to verify this and look for any other problems.
> We expect to not see:
> 1.  The ten second amplitude glitch,

Still there, all IFs.  Drop is exactly one per 10 seconds down in 
amplitude to ~70% nominal.  If this is related to the sawtooth (ie 
discontinuous phase breaking LO lock) then this might not appear for 
sources in certain parts of the sky where the fringe rate relative to 
array center is near enough to zero.

> 2.  the sawtooth in phase with ten second period,

On 13-15 AC there in X-band is no obvious sign of this, but I still claim 
to see some phase behavior with 10 second intervals.  The phase is a 
continuous function of time, but is 'lumpy' to coin a new term.  Is it 
possible that the fix that went into the linear term should have gone into 
the quadratic term?  I claim the phases are still 'rampy' (ie 
discontinuous at 10sec boundaries) on 13 BD, 14, 16, 18.

On closer look, at K-band where phases are moving a bit more, I claim the 
phase(t) is not quite continuous -- there is a much reduced discontinuity 
at the 10 second boundaries on AC compared to BD.  Curvature in phase(t) 
within each 10 second interval is quite clear in AC.

13BD Still shows ramps.

> 3.  phase jumps when returning to the same frequency.

Somehow don't have the data I expected to for this test???


It might be good for someone else to load the data and have a look 
themselves.

vlaobs   = 'TBRISK'
refdate  = '20060530'
timerang = 0,23,0,0,0,23,50,0


-Walter