[evlatests] EVLA phase rates

[George Moellenbrock]

Folks,

A few initial impressions of my test observation this morning:

1. Antennas 14 & 16 participated, apparently after some difficulty getting
them going.  Usable data begins ~2 hours after the start of the 3.5 hour
observation.  This has been a problem in all 5 of my tests this month.

2. Data to Antenna 14 IF C (LCP) looks noise-like.  RCP on 14 looks
ok.  Both pols on 16 look ok.

3. The high phase rates discussed earlier this week are still present on
Antenna 16 in both pols (when bad in one pol, also bad in the other).  As
before, not all scans show this problem, and there does not seem to be a
simple correlation with specific L6 settings.  Also, like before, the
excessive rate seems to oscillate between very high (1000s deg/min) and
tolerable (~100 deg/min) rates on a timescale of 3-6s.

4. Antenna 14 (RCP) also shows the high phase rate problem, in
approximately the the same manner (the period of the rate variation may be
a bit longer), though not in the same setups. 

5. For those of you whom I queried about the VLA correlator's channel
registration, I finally got my scans testing this below the data rate
threshold (barely!), and the result is that the center channel (e.g., 64
out of 127) is indeed centered on the exact center of the nominal band,
i.e., at the freqency given by the signed sum of the LOs plus half
the (total) nominal bandwidth.  Reassuring.

I'll have more details (incl plots) on this observation in the next few
days, as I more carefully reduce the data.

Cheers,
George


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