[evlatests] Data taken with 20 Hz

[Jim Jackson]

Rick,

I'm curious about the comment of Ant 4 taking 3 minutes longer to get on
source. Did the antenna just have to unwrap (implying it was for some
reason starting from a different cable wrap state from the rest of the
antennas) or did something in the FRM or Drive system really cause it to
take that long?  Is this a common occurance for this antenna or is this a
one-off event? Just wondering if Servo or DCS needs to look at this
antenna.

We need to keep an eye on the L302-1 in Antenna 23.  If it keeps doing
that occasionally we may have to add a cable to the 128MHz.

Cheers,
Jim


>     Ken took 40 minutes of data, at X-band, with the 20 Hz synchronous
> power enabled.  He arranged a new scan (but with the same mode -- OSRO1)
> to occur every 40 seconds, to look for scan-induced phase jumps.
>
>     Results:
>
>     a) No phase jumps were seen associated with any of the scan changes.
>
>     b) Only one phase jump of any kind was observed: on both the AA and
> CC correlations on antenna 23, about 5 minutes into the test.
>
>     c) Two '1dB' amplitude jumps were noted, one on antenna/IF 28C, one
> on antenna/IF 25A.
>
>     d) 26 antennas fringed nicely (6 and 10 are still out of the
> array).  Antenna 4 was about 3 minutes late to get on source.
>
>     e) IFs AC showed now blanks in any polarization.  IFs BD were
> littered with blanks -- not antenna based.  On the LCP side (correlation
> DD), baselines 5 x 8, 13, 15, 17, 21, 24, 25 and 27 were 99% blanked
> (the surviving 1% looked fine).  Also, 2 x 9, 4 x 7, 7 x 9, 8 x 19 and 8
> x 23.  A different set of baselines were absent most data on the BB
> (RCP) correlation.
>
>     g) Various periodicities were seen in phase -- all periods were
> longer than 40 seconds, and have nothing to do with scan changes.  The
> amplitudes were small (few degrees) -- could be atmosphere?
>
>     h) Amplitude stability was poorer than expected (variations of 1% or
> so -- my standards are high!).  We await gain correction via switched
> power before offering a speculation as to origin.
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