[evlatests] P-Band cross-polarization

[Frank Schinzel]

This list of antennas agrees mostly with my last check on 
cross-polarization power on May 22nd. This is based on 3C147 data and 
uses the 16 MHz spectral window with center frequency 312 MHz. See 
attached plot.

ea01, 4, 12, 13, 20, 25, and 26 are the worst, which indicates the 
misalignment of dipoles Rick is seeing.

     Frank


On 06/06/2017 03:55 PM, Rick Perley wrote:
>     A recent test has allowed a proper calibration of the 'leakages' 
> for P-band.
>
>     We are all fairly sure that the dominant term in this comes from 
> misorientation of the dipoles.  The cross-polarization solutions are 
> all very constant in frequency, with little frequency structure -- 
> this is consistent with a rotation origin.
>
>     The solutions are made with ea18 as the reference.  So the 
> resulting cross-polarizations reflect (mostly) the misorientation of 
> the dipoles w.r.t. this antenna.
>
>     I find there are two 'families' -- about 2/3 of the antennas have 
> cross-polarizations of 3% or less.  This is very good.  The other 1/3 
> are at the 8 -- 12% level.  This corresponds to a rotation of about 5 
> degrees -- not much, but noticeable.
>
>     The 'high polarization/rotation' antennas are:
>
>     ea01, 4, 8, 9, 12, 20, 25, 26 and 28.
>
>     The current (AIPS) software seems to correctly remove these 
> leakages from the cross-polarized correlations.
>
>
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