[evlatests] Strange differential bandpasses

[Rick Perley]

So, on a probably drier day, the effect is nearly invisible. Support for 
the idea that water/dew on the window is a contributing factor ...

Rick

On 8/27/21 9:42 AM, Drew Medlin wrote:
> Here's an observation from a drier time of year. 2021-03-27, afternoon 
> observation, operator recorded Sky cover 40%. Cumuliform clouds.
>
>
> 20A-092.sb39518402.eb39548999.59300.832225300925.ms-J0303+4716-bb12-PHASE-amp_vs_freq-LL_RR.png
>
>
>
>
> Drew Medlin
> dmedlin at aoc.nrao.edu <mailto:dmedlin at aoc.nrao.edu>
>
> Scientific Data Analyst - VLA Scientific User Support Group
> National Radio Astronomy Observatory
>
>> On Aug 27, 2021, at 9:18 AM, rperley <rperley at nrao.edu 
>> <mailto:rperley at nrao.edu>> wrote:
>>
>> Certainly is reasonable.  In the case I analyzed, the start of the 
>> run was around sunrise, the end around noon.  The period of the 
>> oscillations (and the phase) did not appear to change, however.  The 
>> change in amplitude was quite obvious.
>>
>> I don't know if there was rain on the day I looked at -- but perhaps 
>> dew on the window would do the trick ...
>>
>> Rick
>>
>> On 2021-08-27 11:11, Ken Sowinski wrote:
>>> On Fri, 27 Aug 2021, Rick Perley via evlatests wrote:
>>>> Drew, et al.:
>>>> Perfect!  Period shown in that C-band plot is about 100 MHz, which 
>>>> corresponds pretty closely to the expected value corresponding to 
>>>> the length of the horn.  Good evidence for a mismatch between the 
>>>> window and the OMT….
>>> The change in the sinusoiid should correlate with temperature.
>>> Might the reflections have been exacerbated by moisture from
>>> all the recent rain?
>
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