[evlatests] WIDAR P-band status update: 01OCT2014

[Huib Intema (NRAO)]

Dear P-banders,


Here is the outcome of a short VLA WIDAR P-band status test (few minutes
on 3C295) we ran on Oct 1. EA26 was out. Major points of attention are:

+ EA11 now has normal gains & polarizations (thanks for the fix!)
+ EA17 now has normal gain and bandpass in LCP (thanks for the fix!)

~ EA04 has normal power in both polarizations (may be intermittent)
~ EA16 no longer has low gain and erratic bandpass in RCP (maybe
intermittent)
~ EA19 no longer has low gain in RCP (may be intermittent)

- EA17 has swapped polarizations (should be fixed now, but needs to be
checked)
- EA18 has low power in RCP
- EA28 has very high power, >3 times the median of the other antennas
(may be intermittent)


-- 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:
- EA17 (update: has been addressed on 04OCT, so should be OK now)

* Antenna power levels (determined from gain calibration):
Most antennas have similar (healthy) power levels, within ~30 percent of
the median, except:
- EA18 RCP: P = 0.21
- EA28 RCP: P = 3.30
- EA28 LCP: P = 4.09
(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
- 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 (0.05-0.10, or 5-10 percent) amplitude in
the crosshand correlations RL and LR, except:
- EA04: A = 0.13
- EA15: A = 0.13
- EA19: A = 0.13
- EA20: A = 0.13
- EA23: A = 0.15
- EA28: A = 0.14
(A = polarization leakage, relative to the parallel hand signal)