[daip] [Fwd: ACCOR output]

[lincoln greenhill]

Thank you Craig.  Your detailed recollection is very helpful.

Best,
L.


Craig Walker wrote:
> I looked at the actual power levels in the BBCs for that run and they 
> were low, and variable, in channels 5 and 7 (higher frequencies LCP). 
> These are the power levels after the autoleveling and should be nearly 
> constant.  I'm not sure of the reason, but presumably the power coming 
> down from the antenna was lower than it should have been.  With low 
> autoleveled powers, the clipper levels will not be at the right fraction 
> of total power and you will see exactly what your plot shows.  Hopefully 
> the ACCOR corrections will do what is needed to fix things up.  There 
> will be a small loss of SNR, but I don't think it should be very bad. 
> But you might want to avoid using those channels as part of your 
> absolute amplitude calibration (ANTUSE in CALIB).
> 
> I checked a later run of your project and don't see any sign of the 
> problem.  I presume whatever the trouble was, it got fixed.  The system 
> does let the operators know about low power, but it is likely to take 
> site tech intervention to fix it and that would generally not be done 
> during a run.
> 
> Cheers,
> 
> Craig
> 
> 
> 
> 
> Ingyin Zaw wrote:
>> The expt was in Jan. 2008. Thanks,
>> Ingyin
>>
>> On Tue, 21 Apr 2009, lincoln greenhill wrote:
>>
>>> Dear Leonid, Craig,
>>>
>>>
>>> Attached is a plot showing output from ACCOR (3 VLBA stations, 8 IFs 
>>> overplotted) for a 22 GHz phase referencing expt in Nov. 2004.
>>>
>>> We used solint = -0.25 .
>>>
>>> I have not previously see the signature shown here for OV, where 2 of 
>>> 8 IFs
>>> show a rapid and systematic variation in sampler statistics.  Is the
>>> behavior familiar?  Do you know what could cause it?
>>>
>>> Best, L.
> 

-- 
Lincoln J. Greenhill               Harvard-Smithsonian Center for Astrophysics
Office:     1 617-495-7194         60 Garden St, Cambridge, MA 02138
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