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

[Bryan Butler]

we may not be able to run a test this afternoon, but we'll run one as 
soon as we can.


Huib Intema (NRAO) wrote, On 9/18/14 12:55 :
> Hi Dan,
>
> Thanks for the list; I'm happy to see most things confirmed. Hopefully
> we'll run a P-band test this afternoon, so I can verify the EA11 fix.
>
> The ripples on EA08 and EA13 have gone mostly unnoticed so far because
> their frequency width is close to the 16 MHz spectral window width with
> which we observe in P-band (16 x 16MHz). The ripples are clearly there,
> but may be somewhat more difficult to see these in the plots you use.
>
> -- Huib
>
>
> On 18-Sep-14 11:58, Dan Mertely wrote:
>> 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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>>>
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