[daip] [!16009]: AIPS - FRING FRNSRC: MIN FFT IN FREQ REQUESTED 1003040 MAX ALLOWED 262144

[NRAO Helpdesk]

Eric Greisen updated #16009
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       Staff (Owner): Eric Greisen (was: -- Unassigned --)
              Status: Closed (was: Response Overdue)
           Reply due: - Cleared - (was: 21 April 2020 06:04 AM)

FRING FRNSRC: MIN FFT IN FREQ REQUESTED 1003040 MAX ALLOWED 262144
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           Ticket ID: 16009
                 URL: https://help.nrao.edu/staff/index.php?/Tickets/Ticket/View/16009
                Name: Eskil Varenius
       Email address: varenius at chalmers.se
             Creator: User
          Department: AIPS Data Reduction
       Staff (Owner): Eric Greisen
                Type: Issue
              Status: Closed
            Priority: Default
      Template group: Default
             Created: 03 April 2020 05:52 AM
             Updated: 07 April 2020 05:07 AM
Hi Eric,
Thank you very much for the quick reply. Yes, the frequency setup is a mess. This is an unusual experiment, which I was not involved in before getting some data to look at. After iterating with colleagues we will probably re-correlate these data with different/smaller bands to avoid the overlap issues. But, I still wanted to try your good advice to learn if it works or not. 
I first tried NOIFS on the S/X data, but it refused with "FNDFRQ: AXIS11 CENTER FREQUENCY NOT ON CHANNEL"
I then did UVCOP to slice out the interesting X-bands, and reduce the overlap, which resulted in this frequency setup:

Frequency Table summary uses reference channel     9.00FQID IF#      Freq(GHz)      BW(kHz)   Ch.Sep(kHz)  Sideband  Bandcode   1   1       8.21091188    2125.0000    125.0000      1       2       8.21491188    2125.0000    125.0000      1       3       8.25491188    2125.0000    125.0000      1       4       8.45067188    2125.0000    125.0000      1       5       8.46607188    2125.0000    125.0000      1       6       8.46992188    2125.0000    125.0000      1       7       8.47377188    2125.0000    125.0000      1       8       8.48902188    2125.0000    125.0000      1
However, NOIFS still fail, now with message
FNDFRQ: AXIS 5 CENTER FREQUENCY NOT ON CHANNEL
NOIFs work for bif=1; eif=4 and bif=6;eif 8. But if I involve IF5 in any way, it fails. I was under the impression that NOIFs would deal with this tiny overlap? Perhaps it is because the IFs are not regularly spaced?
Re COVID-19: I hope you and your colleagues are safe and well.
Kind regards
Eskil

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