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Paul/Vivek: The most likely explanation for the scatter seen in A2C2 calibration solutions is strong RFI near 6200 MHz that is compressing the 3-bit samplers. This signal is strongest in antennas near the ends of west (ea24) and north (ea17, ea18, ea22) arms. The likely source is one of the nearby hilltop transmitters, and the pattern of antennas affected has to do with direction to the source combined with antenna pointing.
Dave: There is a standard Point-Point 30MHz channel allocation centered at 6197.24 MHz which fits.
Vivek via vla-test-maint: https://science.nrao.edu/facilities/vla/observing/RFI/Oct-2021-B-configuration/C-Band_spectra_202110B
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2021-22 B config:
ea06 [N32], ea17 [N36], ea18 [N28], ea22 [N24], ea24 [W36], ea26 [W32]
ea18,ea22,ea24 A2C2 always have it, though sometimes mild. ea06,ea17,ea26 occasionally have it.
Easily seen in finalcals stage of pipeline, "final amp time cal" and "final amp freq cal" tabs.
example pipeline products here:
/lustre/aoc/sciops/estarr/data/C_band_examples/
previews below:
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