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<div class="moz-text-flowed" style="font-family: -moz-fixed;
font-size: 14px;" lang="x-western">Dear P-banders,
<br>
<br>
Here is the combined outcome of two short VLA WIDAR P-band status
tests (few minutes on 3C48) we ran on Sept 5 and 13. EA26 was out
in both. Major points of attention are:
<br>
<br>
+ EA20 no longer shows the huge bandpass ripple on LCP
(thanks for the fix!)<br>
<br>
~ EA23 no longer shows the large bandpass ripple on RCP<br>
Was this fixed or is this intermittent?
<br>
<br>
- EA04 has very low gain in RCP, and low gain in LCP<br>
- EA08 has large bandpass ripple in LCP<br>
- EA11 has either loose / rotated feed, or swapped polarizations +
huge polarization leakage<br>
- EA13 has large bandpass ripple in LCP<br>
- EA14 has low gain in RCP<br>
- EA16 has low gain and erratic bandpass in RCP (Sept 13 only)<br>
- EA17 has swapped polarizations and low gain in LCP (after
software swap)<br>
- EA18 has low gain
in RCP<br>
- EA19 has low gain
in RCP<br>
- EA28 has fast bandpass ripple on LCP<br>
<br>
-- Huib
<br>
<br>
<br>
<br>
I've used the same analysis approach as previously, therefore can
be interpreted in the same way. Antenna EA26 was not in the array.
The following polarization labeling convention applies: RCP =
horizontal dipole(s), LCP = vertical dipole(s).
<br>
<br>
* Swapped polarizations:
<br>
- EA11 (or possibly a rotated feed)<br>
- EA17 (after the dipole fix)
<br>
<br>
* Antenna power levels (determined from gain calibration):
<br>
Most antennas have similar (healthy) power levels, within ~30
percent of the median, except:
<br>
- EA04 RCP: P = 0.05<br>
- EA04 LCP: P = 0.40<br>
- EA14 RCP: P = 0.35 <br>
- EA16 RCP: P = 0.35 <br>
- EA18 RCP: P = 0.45<br>
- EA19 RCP: P = 0.45<br>
(P = power level relative to median)
<br>
<br>
* Bandpass ripples (determined from bandpass calibration):
<br>
Most antennas have (healthy) smooth bandpass amplitude structure
and linear phase structure across frequency (224-480 MHz; ignoring
the ranges with known RFI), except:
<br>
- EA02 RCP: A = 0.15, F = 5.9 MHz, L = 25.5 m
<br>
- EA02 LCP: A = 0.15, F = 6.2 MHz, L = 24.0 m
<br>
- EA08 LCP: A = 0.30, F = 17. MHz, L = 8.7 m<br>
- EA13 LCP: A = 0.35, F = 20. MHz, L = 7.5 m<br>
- EA14 RCP: possible large ripple, F ~ 75. MHz, L = 2.0 m<br>
- EA16 RCP: erratic bandpass<br>
- EA17 LCP: upturn in upper 1/4th of the band<br>
- EA28 LCP: A = 0.25, F = 3.6 MHz, L = 42.0 m
<br>
(A = relative ripple peak-peak amplitude, F = the ripple frequency
width , L = associated cable length)
<br>
<br>
* Polarization leakage (determined from a single, RFI-free 16 MHz
subband):
<br>
Most antennas show a non-zero (0.10-0.15, or 10-15 percent)
amplitude in the crosshand correlations RL and LR, except:
<br>
- EA11: A = 0.42(!)
<br>
(A = polarization leakage, relative to the parallel hand signal)
<br>
<br>
<br>
<br>
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