[evlatests] Strange Phase Behavior for ea22

[Leon Abeyta]

I noticed that the L305 in ea22 is being over-driven by a few dB. If 
anyone is interested, I can investigate fixing that on a maintenance day.

Leon Abeyta

On 2/26/2020 10:34 AM, Rick Perley via evlatests wrote:
>      Beam cuts were taken last night, as part of our optics alignment 
> program.    Bands observed were from X through Q. Stability was 
> exceptional (as we might expect on a cold, clear, calm night).
> 
>      All antennas behaved exceptionally well, except one.  ea22 has 
> phase oscillations many times larger than they should be.
> 
>      Ea22 is at W10.  Using ea28 (at W8) as a reference, I compared the 
> phase behavior of the baseline ea28 -- ea22 to that of ea28 -- ea26. The 
> latter is at W6, so the baselines are of comparable length.  Below is a 
> short table, showing the amplitude of the phase fluctations.  These were 
> established from the CALIB gains, over the 45 seconds that were spent on 
> the four calibrator observations.
> 
>      Band             ea26        ea22
> 
> -------------------------------------------
> 
>      X                    <1            8 degrees
> 
>      Ku                    1            15 - 20
> 
>      K                     2                15
> 
>      Ka                    6                >20
> 
>      Q                    4                40 -- 50
> 
> -----------------------------------------------------
> 
>      Both polarizations behave identically.  The fluctuations scale 
> roughly with frequency.  The character of the fluctuations is 
> essentially identical to atmospheric -- except they are 10 times too 
> large.  No other antenna (even those at the ends of the arms) showed 
> fluctuations anywhere near what ea26 has.
> 
>      So unless we're willing to believe that the atmosphere is 'special' 
> above ea26, and no other, there's something not right with the phase 
> tracking for that antenna.
> 
> 
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