[evlatests] S-band Polarization

[Emmanuel Momjian]

The polarization of the S-band receivers on antennas 8, 9, 24, 27, and 28,
has been assessed across the full band.

The source 3C147 was observed, and the ratios RL/RR and LR/LL were measured
in the IF pairs AC and BD separately.

3C147 is an unpolarized source, thus the cross-hand amplitudes, providing
the delays are set, give the polarization leakage directly. Dividing by RR
or LL gives a good estimate of the antenna percentage polarization.

Note that these results are preliminary. Also, PCAL was not run on these
data.

Excluding band-edge effects, the results show that baselines amongst
antennas 9, 27, and 28 have the lowest values (2-4% on average) for RL/RR
and LR/LL in both IF pairs.

Baselines to antennas 8 and 24 have higher values (5-8% on average) in both
IF pairs. Their performance further degrades below 2250 MHz (12-14% on
average) in the LR/LL terms that involve antenna 8, and in both RL/RR and
LR/LL terms that involve antenna 24.
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