[evlatests] VLA System health

Bryan Butler bbutler at nrao.edu
Thu Mar 7 00:24:19 EST 2013


i'm curious why our normal stress test isn't finding these issues?  i 
thought that was the whole point of those observations.

	-bryan


Rick Perley wrote, On 3/6/13 12:00 :
>      From the short test, preparing for the 'flux densities', I find:
>
>      1) L-band:  All antennas o.k., all PDifs are plausible.
>
>      2) S-band:  No fringes or PDif from ea03 -- presumably, the receiver
> is not yet in?  ea06, on IF 'A' gives a sinusoidally varying PDif of 20%
> amplitude, and 1 minute period.  (It has always done this).
>
>      3) C-band:  All antennas fringe.  ea14 gives a negative, or
> extremely weak, PDif on all IFs.
>
>      4) X-band:  No fringes from ea20.  PDif = 0 from ea02 and ea20.
> Both antennas show healthy PSum.  ea14 has very low PDif, but o.k. PSum.
>
>      5) Ku-band:  No fringes from ea23, but PSum and PDif both normal.
> ea10 is showing large gain changes from scan to scan (0.7 dB).  All
> others o.k.
>
>      6) K-band:  No fringes from ea23, and PDif is very small (Tsys
> claimed to be 500K).  Ea07 has system temeprature of about 300K.  All
> others o.k.
>
>      7) Ka-band:  No fringes from ea23, and PDif equal zero on all IFs.
> (Or, Tsys >1000 K).  All others o.k.
>
>      8)  Q-band:  No fringes from ea 23 on IFs B and D (and PDif = 0).
> Fringes seen on IFs A and C.
>                           ea08 gives zero PDif on all IFs.
>                           Very high Tsys (> 200K) on ea 7 and ea18.
>
>      The lack of fringes from ea23 for Ku, K, Ka and Q band seems to
> indicate a problem with the UX downconverter
>
>
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