0000278: 5cm: Correlation amplitude and phase versus time had a small scale irregular variation in all subbands
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ID Category Severity Reproducibility Date Submitted Last Update
0000278 [VLBI] 0.unknown/unspecified minor have not tried 05-07-10 10:08 11-11-10 11:05
Reporter Geert Kuper View Status public  
Assigned To Geert Kuper
Priority normal Resolution fixed  
Status resolved  
Summary 0000278: 5cm: Correlation amplitude and phase versus time had a small scale irregular variation in all subbands
Description Feedback from JIVE:

Network Monitoring Report: 5cm N10M2.

Wb, Westerbork: Correlation amplitude and phase versus time had a small scale irregular variation in all subbands on all the baselines to Wb
Additional Information WSRT uses one receiver in RT7 for 5cm VLBI.
We use the complete backend with TaduMax and only RT7 in the TAAM-word.
Check with Hans van der Marel.
Possible reasons: RT7 pointing;5cm receiver;IVC;ADC;TAAM;TaduMax
Attached Files

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- Notes
(0000294)
Geert Kuper
16-07-10 08:08

 Hi Bob,
 
About the Network Monitoring Report 5cm N10M1 and N10M2.
 
 
Problem:
-----------
 Jun mentioned the following problem for the wsrt in N10M1 and N10M2 (session 2010-1 and 2010-2) :
 
 'Wb, Westerbork: Correlation amplitude and phase versus time had a small scale irregular variation in all subbands on all the baselines to Wb'
 
 This problem was not found in session 2009-2, a previous 5cm (M-band) session.
 
 
WSRT vlbi 5cm setup description:
--------------------------------------
We have only one 5cm receiver. This receiver is always placed in RT7.
We use the complete backend but only RT7 is specified in the adding section.
The receivers in all telescopes get the same 5cm frequency steering.
Only RT7 will give proper output. The output of the receivers in the other RT's are undefined, and therefore they need to be attenuated.
 
Investigation:
---------------
I did some investigation to find the differences between 5cm sessions.
It turned out that for 5cm session 2009-2 proper attenuation settings had been used.
This was not the case for 5cm session 2010-1 and 2010-2.
 
 
Conclusion:
-------------
As this was the only difference that could be found, this may have been the cause of the problem. This was confirmed by Hans van der Marel .
Of course we can only be certain after the next 5cm NME feedback.
 
 
Prevention in the future:
---------------------------
All system parameter files for 5cm VLBI have been set on maximum attenuation for all RT's except RT7.
In the WSRT VLBI wiki there is now a clear remark to tune only the Total Power output of RT7.
 
 
Cheers
Geert.
 
 
 

- Issue History
Date Modified Username Field Change
05-07-10 10:08 Geert Kuper New Issue
05-07-10 10:08 Geert Kuper Assigned To  => Hans van der Marel
05-07-10 10:08 Geert Kuper Status new => assigned
06-07-10 12:55 Geert Kuper Assigned To Hans van der Marel => Geert Kuper
16-07-10 08:08 Geert Kuper Note Added: 0000294
16-07-10 08:08 Geert Kuper Resolution open => fixed
11-11-10 11:05 Geert Kuper Status assigned => resolved