[evlatests] L-Band Polarization

[Ken Sowinski]

I have reformatted Rick's table to make more readable to me
and thought others would benefit if my mailer does not mess
it up.


>From rperley at nrao.edu Fri Feb  2 17:05:36 2007
Date: Fri, 02 Feb 2007 17:05:09 -0700
From: Rick Perley <rperley at nrao.edu>
To: evlatests at aoc.nrao.edu
Subject: [evlatests] L-Band Polarization

     Bob Hayward noted that EVLA antenna 23 has by far the best
ellipticity, as measured in the lab, so should make a good reference
antenna for polarization.

     Rerunning the 'PCAL' program with 23 as reference gives the
following 'D-terms' (in percent).  Roughly speaking the numbers give
the false degree of linear polarization on a baseline to antenna 23,
for an unpolarized source.

Freq     13     14     16     17     18     23     24    26
-------------------------------------------------------------

1250 R   2.4    4.5    3.0    3.5    6.8    0.0    5.9   7.1
1250 L   2.5    9.1    7.3    8.9    6.9    1.3    5.4   5.3

1360 R   DNT   10.7    4.3    5.6    3.8    0.0    7.2   9.3
1360 L   DNT    9.4    2.8   10.9    3.1    2.0    7.2   9.0

1485 R   6.2    6.9    2.1    7.6    2.3    0.0    5.7   8.2
1485 L   4.0   10.2    4.0   12.1    5.0    4.3    7.0   8.3

1612 R   1.8    7.4    1.8    4.1    1.7    0.0    6.0   6.9
1612 L   2.5    8.3    2.0    8.5    2.1    1.8    6.7   9.0

1725 R   4.1    6.3    3.5    3.6    1.2    0.0    6.1   5.6
1725 L   3.8    7.6    2.8    5.0    1.7    1.7    6.7   4.8

1825 R   3.0    7.7    2.0    1.6    2.9    0.0    5.8   3.3
1825 L   6.2    8.2    2.9    8.0    0.1    2.9    8.3   8.2

1950 R  14.0    7.4   11.0    1.4    3.8    0.0    5.1   4.3
1950 L   6.4   10.0    1.6    4.1    2.4    6.0    5.4   4.0
-------------------------------------------------------------

DNT = 'Did Not Tune'

Some EVLA antennas -- nnotably 16 and 18 (for a reasonable part of the
frequency range) have quite low spurious polarizations when matched
against antenna 23.  Some (notably antenna 14) are rather worse.  All
are quite poor at 1950 MHz -- but at this far end of the range, good
results were not expected.


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