[evlatests] WIDAR P-band status update: 13SEP2014

[Dan Mertely]

Thanks Huib.  Here is my review, taken from previous maintenance
action notes, and this week's all-antenna bandpass plot analysis
(\\filehost\evla\techdocs\rfi\rfi-survey\plots\evla-bandpass\p-band\20140916-all).

1)  ea20: yes, we fixed a cabling problem up at the apex.
2)  ea23: yes, we fixed a cabling problem up at the apex.
3)  ea04: RYH side has 80 MHz ripple, weak RFI SNR.  Needs on ant checkout.
4)  ea06: RYH side has 80 MHz ripple, weak RFI SNR.  Needs on ant checkout.
5)  ea08: bandpasses look OK.
6)  ea11: dipole was rotated.  Pol s/b OK. How are the amps?
7)  ea13: bandpasses look OK.
8)  ea14: LXV side has weak RFI SNR at low end.
9)  ea16: RYH side has 80 MHz ripple, weak RFI SNR.  Needs on ant checkout.
10) ea17: RYH side has 80 MHz ripple, weak RFI SNR.  Needs on ant checkout.
11) ea18: has odd image and noise on IFD.
12) ea19: has odd image and noise on IFA & IFC

-Mert




On 9/16/2014 2:38 PM, Huib Intema (NRAO) wrote:
> Dear P-banders,
>
> 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:
>
> + EA20 no longer shows the huge bandpass ripple on LCP (thanks for the fix!)
>
> ~ EA23 no longer shows the large bandpass ripple on RCP
>    Was this fixed or is this intermittent?
>
> - EA04 has very low gain in RCP, and low gain in LCP
> - EA08 has large bandpass ripple in LCP
> - EA11 has either loose / rotated feed, or swapped polarizations + huge
> polarization leakage
> - EA13 has large bandpass ripple in LCP
> - EA14 has low gain in RCP
> - EA16 has low gain and erratic bandpass in RCP (Sept 13 only)
> - EA17 has swapped polarizations and low gain in LCP (after software swap)
> - EA18 has low gain in RCP
> - EA19 has low gain in RCP
> - EA28 has fast bandpass ripple on LCP
>
> -- Huib
>
>
>
> 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).
>
> * Swapped polarizations:
> - EA11 (or possibly a rotated feed)
> - EA17 (after the dipole fix)
>
> * Antenna power levels (determined from gain calibration):
> Most antennas have similar (healthy) power levels, within ~30 percent of the
> median, except:
> - EA04 RCP: P = 0.05
> - EA04 LCP: P = 0.40
> - EA14 RCP: P = 0.35
> - EA16 RCP: P = 0.35
> - EA18 RCP: P = 0.45
> - EA19 RCP: P = 0.45
> (P = power level relative to median)
>
> * Bandpass ripples (determined from bandpass calibration):
> Most antennas have (healthy) smooth bandpass amplitude structure and linear
> phase structure across frequency (224-480 MHz; ignoring the ranges with known
> RFI), except:
> - EA02 RCP: A = 0.15, F = 5.9 MHz, L = 25.5 m
> - EA02 LCP: A = 0.15, F = 6.2 MHz, L = 24.0 m
> - EA08 LCP: A = 0.30, F = 17. MHz, L = 8.7 m
> - EA13 LCP: A = 0.35, F = 20. MHz, L = 7.5 m
> - EA14 RCP: possible large ripple, F ~ 75. MHz, L = 2.0 m
> - EA16 RCP: erratic bandpass
> - EA17 LCP: upturn in upper 1/4th of the band
> - EA28 LCP: A = 0.25, F = 3.6 MHz, L = 42.0 m
> (A = relative ripple peak-peak amplitude, F = the ripple frequency width , L =
> associated cable length)
>
> * Polarization leakage (determined from a single, RFI-free 16 MHz subband):
> Most antennas show a non-zero (0.10-0.15, or 10-15 percent) amplitude in the
> crosshand correlations RL and LR, except:
> - EA11: A = 0.42(!)
> (A = polarization leakage, relative to the parallel hand signal)
>
>
>
>
>
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