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<p style="-qt-paragraph-type:empty; margin-top:0px;
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-qt-block-indent:0; text-indent:0px;">Dear testers,
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<p style=" margin-top:0px; margin-bottom:0px; margin-left:0px;
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the outcomes of a short VLA WIDAR P-band status test (few minutes
on 3C48) we ran this morning. I have condensed the output a bit.
Major points of attention are:</p>
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<p style=" margin-top:0px; margin-bottom:0px; margin-left:0px;
margin-right:0px; -qt-block-indent:0; text-indent:0px;">+ EA12 and
EA16 no longer have swapped polarizations</p>
<p style=" margin-top:0px; margin-bottom:0px; margin-left:0px;
margin-right:0px; -qt-block-indent:0; text-indent:0px;">+ EA16 LCP
is now alive and working fine</p>
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<p style=" margin-top:0px; margin-bottom:0px; margin-left:0px;
margin-right:0px; -qt-block-indent:0; text-indent:0px;">- EA06 LCP
has lower power</p>
<p style=" margin-top:0px; margin-bottom:0px; margin-left:0px;
margin-right:0px; -qt-block-indent:0; text-indent:0px;">- EA17 has
increased polarization leakage<br>
- EA20 LCP has a large standing wave issue</p>
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<p style=" margin-top:0px; margin-bottom:0px; margin-left:0px;
margin-right:0px; -qt-block-indent:0; text-indent:0px;">Thanks to
Paul, Jerry and Mert for repairing EA12 and EA16!</p>
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<p style=" margin-top:0px; margin-bottom:0px; margin-left:0px;
margin-right:0px; -qt-block-indent:0; text-indent:0px;">-- Huib</p>
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<p style=" margin-top:0px; margin-bottom:0px; margin-left:0px;
margin-right:0px; -qt-block-indent:0; text-indent:0px;">---</p>
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<p style=" margin-top:0px; margin-bottom:0px; margin-left:0px;
margin-right:0px; -qt-block-indent:0; text-indent:0px;">I've used
the same analysis approach as previously, therefore can be
interpreted in the same way. Antenna EA13 was not in the array,
and EA14 was not active. The following polarization labeling
convention applies: RCP = horizontal dipole(s), LCP = vertical
dipole(s).</p>
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<p style=" margin-top:0px; margin-bottom:0px; margin-left:0px;
margin-right:0px; -qt-block-indent:0; text-indent:0px;">* Swapped
polarizations: None!</p>
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<p style=" margin-top:0px; margin-bottom:0px; margin-left:0px;
margin-right:0px; -qt-block-indent:0; text-indent:0px;">* Antenna
power levels (determined from gain calibration):</p>
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<p style=" margin-top:0px; margin-bottom:0px; margin-left:0px;
margin-right:0px; -qt-block-indent:0; text-indent:0px;">All
antennas have similar (healthy) power levels, within ~30 percent
of the median. Taking the median of these power levels as the
reference, I found the following deviations:</p>
<p style=" margin-top:0px; margin-bottom:0px; margin-left:0px;
margin-right:0px; -qt-block-indent:0; text-indent:0px;">- EA06 LCP
= 0.36</p>
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<p style=" margin-top:0px; margin-bottom:0px; margin-left:0px;
margin-right:0px; -qt-block-indent:0; text-indent:0px;">* Bandpass
ripples (determined from bandpass calibration):</p>
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<p style=" margin-top:0px; margin-bottom:0px; margin-left:0px;
margin-right:0px; -qt-block-indent:0; text-indent:0px;">Most
antennas have (healthy) smooth bandpass amplitude structure and
linear phase structure across frequency (224-480 MHz), ignoring
the ranges with known RFI. Larger ripples are seen on some
antennas/polarizations. For each of these, the relative ripple
peak-peak amplitude (A >= 0.20), the frequency width (F) and
the associated cable length (L) are estimated:</p>
- EA08 LCP: A = 0.30, F = 19 MHz, L = 7.9 m<br>
- EA20 LCP: A = 0.45, F = 16.2 MHz, L = 9.3 m
<p style=" margin-top:0px; margin-bottom:0px; margin-left:0px;
margin-right:0px; -qt-block-indent:0; text-indent:0px;">- EA21
LCP: A = 0.20, F = 6.2 MHz, L = 48.0 m</p>
<p style=" margin-top:0px; margin-bottom:0px; margin-left:0px;
margin-right:0px; -qt-block-indent:0; text-indent:0px;">EA20 LCP
ripple is by far the most serious. EA08 LCP went unnoticed until
now.</p>
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<p style=" margin-top:0px; margin-bottom:0px; margin-left:0px;
margin-right:0px; -qt-block-indent:0; text-indent:0px;">*
Polarization leakage (determined from a single, RFI-free 16 MHz
subband):</p>
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<p style=" margin-top:0px; margin-bottom:0px; margin-left:0px;
margin-right:0px; -qt-block-indent:0; text-indent:0px;">After
applying flux- and bandpass calibration, all antennas show a
non-zero amplitude in the crosshand correlations RL and LR.
Averaged in time and frequency, most antennas have a 0.05-0.10
amplitude signal (5-10 percent) in RL and LR relative to RR and LL
(here, the median amplitude was calculated from the antenna to all
other antennas). The following antennas have crosshand signals
above 0.12:</p>
- EA04 = 0.13<br>
- EA17 = 0.17<br>
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