[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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