[evlatests] P-band status update: 15APR2014

[Huib Intema (NRAO)]

Dear testers,

Here are the outcomes of a short VLA P-band status test (few minutes on 
3C147) we ran today around noon. I've used the same analysis approach as 
previously (26MAR2014; see e-mail included below), therefore can be 
interpreted in the same way. Antenna EA14 was out of the array, while 
antenna EA03 was dead. The following polarization labeling convention 
applies: RCP = horizontal dipole(s), LCP = vertical dipole(s).

Improvements compared to the previous test:
- EA04 LCP had low power, now 'normal'
- EA05 RCP and LCP had low power, now 'normal'
- EA16 RCP had low power, now 'normal'
- EA07 LCP had bandpass ripple, now 'normal'
- EA10 LCP had bandpass ripple, now 'normal'
- EA16 RCP had bandpass ripple, now 'normal'
- EA22 had high cross-polarization, now 'normal'

These changes reflect the work that Paul, Mert, Greg and company have 
put into fixing things (thanks!).

-- Huib


* Antenna power levels (determined from gain calibration):

All antennas have similar (healthy) power levels, within a factor of two 
of the median. Taking the median of these power levels as the reference, 
I noticed a few marginally low outlier antenna / polarization pairs with 
the following relative power levels:
- EA06: LCP = 0.51
- EA13: RCP = 0.55
- EA19: RCP = 0.46


* 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. The following antenna/polarization pairs show 
clear evidence of ripples in amplitude and/or phase across frequency, 
indicating standing wave issues; for each the relative ripple peak-peak 
amplitude (A), the frequency width (F) and the associated cable length 
(L) are estimated:
- EA20 RCP: A = 0.65, F = 20.0 MHz, L = 7.5 m

Similarly, the following antenna/polarization pairs have smaller ripples:
- 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 RCP: A = 0.10, F = 3.4 MHz, L = 43.5 m
- EA11 RCP: A = 0.15, F = 3.3 MHz, L = 45.0 m
- EA11 LCP: A = 0.15, F = 3.8 MHz, L = 39.0 m
- EA28 LCP: A = 0.15, F = 3.8 MHz, L = 39.0 m


* Polarization leakage (determined from a single, RFI-free 16 MHz subband):

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 marginally higher crosshand signals (above 0.10):
- EA04: 0.12 in RL, 0.12 in LR
- EA17: 0.14 in RL, 0.13 in LR
- EA20: 0.13 in RL, 0.12 in LR
- EA26: 0.13 in RL, 0.12 in LR
- EA28: 0.13 in RL, 0.13 in LR








On 28-Mar-14 09:18, Huib Intema (NRAO) wrote:
> Dear testers,
>
>
> Here are the outcomes of a short P-band status test (few minutes on
> 3C147) we ran last Wednesday evening. Antennas EA14 and EA21 were out 
> of the
> array, while antenna EA17 was dead. The following polarization labeling
> convention applies: RCP = horizontal dipole(s), LCP = vertical dipole(s)
>
>
> * Antenna power levels (determined from gain calibration):
>
> Most antennas have similar (healthy) power levels, within a factor of
> two of their median. Taking the median of these power levels as the
> reference, I noticed a few low outlier antenna/polarization pairs with
> the following relative power levels:
> - EA04: LCP = 0.19
> - EA05: RCP = 0.08, LCP = 0.22
> - EA16: RCP = 0.02
>
> Similarly, the following antenna/polarization pairs have marginally low
> relative power levels:
> - EA06: LCP = 0.50
> - EA13: RCP = 0.45, LCP = 0.46
> - EA18: LCP = 0.44
>
>
> * 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. The following antenna/polarization pairs show
> clear evidence of ripples in amplitude and/or phase across frequency,
> indicating standing wave issues; for each the relative ripple peak-peak
> amplitude (A), the frequency width (F) and the associated cable length
> (L) are estimated:
> - EA16 RCP: A = 1.0, F = 87.5 MHz, L = 1.71 m
> - EA20 RCP: A = 0.65, F = 20.0 MHz, L = 7.5 m
>
> Similarly, the following antenna/polarization pairs have smaller ripples:
> - 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 RCP: A = 0.10, F = 3.4 MHz, L = 43.5 m
> - EA10 LCP: A = 0.20, F = 3.3 MHz, L = 45.0 m
> - EA11 RCP: A = 0.15, F = 3.3 MHz, L = 45.0 m
> - EA11 LCP: A = 0.15, F = 3.8 MHz, L = 39.0 m
>
>
> * Polarization leakage (determined from a single, RFI-free 16 MHz 
> subband):
>
> 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 antenna has significantly higher crosshand signals:
> - EA22: 0.26 in RL, 0.27 in LR
>
> Similarly, there was one antenna with a higher signal in just one
> crosshand:
> - EA18: 0.15 in RL, 0.06 in LR
>
>
>
> -- Huib
>
>
>
>
>