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    [PDBI\]SPECTRAL    iunit    bandwidth    fcent    /NARROW   1|2   [/BAND

    Select the width and position of each spectral unit of  the  narrow-band
      - 'iunit' is the correlator unit number (1 to 8)
      - 'bandwidth' is the bandwidth in MHz (20, 40, 80, 160, or 320)
      - 'fcent' is the center frequency (in MHz) of the unit in the
         third IF, i.e. the IF at the entry of the narrow-band correlator
         (in the range 100 to 1100 MHz).
    The  option  /NARROW  is mandatory, and is used to select which entry of
    the correlator the unit is connected to. The  SPECTRAL  command  updates
    the  current plot by drawing the position and width of the selected cor-
    relator unit. The list of the current correlator  setup,  including  the
    number of channels and resolution, is printed out.

    Alternatively,  the  command  "SPECTRAL  iunit"  with no other arguments
    calls the cursor and allows one to  define  interactively  the  spectral
      - Left hand click defines the central freuency and the narrow band
      - +/- increases/decreases the bandwidth
      - < and > shifts the position of the unit by 5 MHz
      - E is used to Exit this mode
    The plot is updated after each action.

    Option  /BAND  LSB|USB|SSB|DSB can be used to define the processing mode
    of the selected correlator unit. There is no  practical  difference  be-
    tween  LSB and USB tunings. The DSB mode provides twice as many channels
    than the LSB or USB modes for the same bandwidth, but the central  chan-
    nels  suffer from the Gibbs effect. This mode is therefore not optimized
    for spectroscopic studies. Choosing between an SSB or DSB mode is possi-
    ble  only  if a bandwidth of 160 or 80 MHz has been selected (320 MHz is
    only available in DSB mode; 40 and 20 MHz are only  available  in  SSB).
    Default is DSB for 320 MHz wide units, LSB for the other bandwidth.  The
    /BAND option has no consequences on the plot produced by ASTRO, but  af-
    fects  the  printout  (number  of channels and resolution) and the setup
    file produced by the PRINT command.

Gildas manager 2018-05-25