[evlatests] Bad polarizer in ea27 at Ka-band

[rperley]

I'm reducing the 'dish holography' data, taken in January 2019 and May 
2020 at Ka-band.  Generally excellent data (although there are some 
problems with wild and crazy pointing).

I included polarization calibration, which has revealed a serious 
problem with ea27's polarizer.  In the 2019 data, the polarization 
solutions for this antenna showed them normal (although higher, at ~7% 
than the others). However, the 2020 data, taken on two days, May 18 and 
May 27, show very high polarization (10 to 20%) with strong frequency 
dependence.  Both solutions show a sharp resonance feature -- but at 
different frequencies on the two days -- near 33.22 GHz on May 18, ad 
33.35 GHz on May 27.

Two plots are attached.

Rick
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