[evlatests] P-band receiver stability

[Rick Perley]

     Ooops ... the last antenna is ea26.

     Rick

On 10/17/2014 04:19 PM, Huib Intema (NRAO) wrote:
> Hi Rick,
>
> Thanks for this report. It is useful to have such a long observing run,
> which allows for uncovering some of the issues that are more difficult
> to spot in the few-minute test observations I usually analyze.
>
> Regarding the "two-gain-state" problem, I have seen antennas that
> misbehave in one test, but not in another. We have had quite a few
> issues with cables (and many thanks to the engineers that have fixed
> most of them), so maybe some of those have half-broken cables. At least
> both EA04 and EA16 have previously been reported as "likely
> intermittent" (e.g., see WIDAR P-band status update: 01OCT2014), as well
> as EA19 and EA28.
>
> I have also noted some time-variability in the gains of some antennas. A
> few also have strong bandpass ripples (like EA13-L/Y), also mostly cable
> issues, which may be what is causing these gain variations. If that is
> true it would be really bad, as it would NOT calibrate out (unless one
> resorts to time-variable bandpass calibration, which is highly
> undesirable).
>
> Note that your antenna list for Y-problems ends with ea2, which suggests
> that a number was dropped. Please confirm.
>
> -- Huib
>
>
>
>
>
> On 17-Oct-14 15:27, Rick Perley wrote:
>>       The 30-hour 'flux models/density' run, taken last weekend, gives
>> much information on receiver stability.  Here is a short report for P-band.
>>
>>       In general, receiver stability is extremely good.  Most
>> antennas/IFs have constant gain to within 5% over the 30 hour period.
>> Most are significant better than this.  (And this without applying the
>> switched power).
>>
>>       The exceptions to this (and some are quite extreme!) are given below:
>>
>>       For the 'X' polarization (to be more precise, that which is
>> labelled as 'X' in the data):
>>
>>       ea04, ea14 and ea21.  The first is especially bad, with two gain
>> states -- one good, the other very bad.  It was in the 'good' state for
>> about 6 continuous hours.
>>
>>       For the 'Y' polarization, the list of misbehaving antennas is longer:
>>
>>       ea03, ea04, ea12, ea13, ea16, ea19, and ea2
>>       ea04 is very very weak most of the time.  ea16 also has two gain
>> states, one normal, the other very not.  The rest show significant time
>> variable performance -- but sufficiently slow that it can be calibrated.
>>
>>       I can provide (next week) plots if these are useful.
>>
>>
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