[daip] [!7226]: AIPS - strange scaling of visibility amps & weights w/ DOBAND=1

[Eric Greisen]

Eric Greisen updated #7226
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              Status: Closed (was: Open)
                 Due: - Cleared - (was: 05 October 2015 03:45 PM)

strange scaling of visibility amps & weights w/ DOBAND=1
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           Ticket ID: 7226
                 URL: https://help.nrao.edu/staff/index.php?/Tickets/Ticket/View/7226
           Full Name: Michael Bietenholz
               Email: mbieten at yorku.ca
             Creator: User
          Department: AIPS Data Reduction
       Staff (Owner): Eric Greisen
                Type: Issue
              Status: Closed
            Priority: Default
      Template Group: Default
             Created: 08 September 2015 05:34 PM
             Updated: 01 October 2015 05:27 PM



Try looking at baseline 1-5.  I can confirm your numbers for 1-3
but it turns out that the average bandpass factor of 1-3 after
shifting the BPs as required by VLBI is about 3/8 so the weight
factor is about 0.13.  For baseline 1-5 it is 0.84 (after squaring).

Antenna 3 has a bandpass that grovels near zero much more than the
other antennas.  And the weight factor to apply has to do with the
average of the entire bandpass (since this is not an analog system but
one with limited bits).  In VLBI it is standard to use all channels, in
the VLA case we do limit to the inner 3/4 of the BP function.

Note that your case has revealed a real issue - the weight scaling
is not applied to the cross hands.  I will fix that.

Eric Greisen




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