[evlatests] More on noise for mode 'PA'

[Mark J Claussen]

Bryan,

I am quite sure that we tested polarization modes, but
the question is how extensive was our testing ... and
would we have noticed this.  Not sure we made too many
images in polarization spectral modes.

Mark


On Mon, April 14, 2008 8:37 pm, Bryan Butler wrote:
>
> as ken said in the coordination meeting this morning, the key date will
> be september 2006 - the point at which the new correlator controller was
> turned on for all observations.
>
> gustaaf & mark - did we not check polarization when we were testing the
> new controller?  i had it in my head that we did, but may be mistaken.
>
> 	-bryan
>
>
> George Moellenbrock wrote:
>>
>>> I then remembered that I had taken data in mode 'PA' for observations
>>> of
>>> 3C273, back in 1997, with the same BW (12.5 MHz) as the recent tests.
>>> I
>>> have loaded these data, and did a quick calibration.  The result of
>>> this
>>> is that there is *no* difference in the noise, as shown by the
>>> histrogram
>>> distributions in real and imaginary parts, of the four correlations.
>>>
>>> Thus, it appears that this problem is a relatively recent development.
>>>
>>
>> Among the most recent of my mode 'PA' instr pol stability and freq-dep
>> tests was an observation in Mar 2006.  In that observation (15ch,
>> L-band),
>> the noise in the cross hands and parallel hands appears to be the same
>> (I
>> am examining the calibrated data).  So I concur with Rick that the
>> problem
>> is a "relatively recent" development (though my definition of
>> "relatively"
>> is a little different than his...), i.e., the problem was introduced
>> AFTER
>> Mar 2006.
>>
>> -George
>>
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