[evlatests] ea25 cross-polarization problem repaired

[Rick Perley]

In reviewing my considerable body of observations of the Moon with our P-band system, it was clear that ea25 had a very high cross-polarization, which was not due to the usual feed dipole rotation.  (This can be distinguished because rotation provides a `real' D-term (real meaning as in complex numbers), and ea25's D-terms had a very large imaginary component).  Only ea25 behaved this way – all others provided the usual 'real-dominated' D-terms.   And, over time, it was clear that this cross-polarization was getting worse.

A week ago Monday, after inspection of the dipoles revealed no abnormalities, the receiver was replaced.

Lilia set up a short  observation yesterday of 3C147 and DA240, which allows a full calibration to be done.

Result:  The cross-polarization of ea25 is now completely normal.

Suggestion:  Somebody should look at the receiver to see if the origin of the leakages between the signal channels can be found.

Rick and Lilia
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