SPECTRAL

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

    Select the width and position of each spectral unit of  the  narrow-band
    correlator.
      - '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
    unit:
      - Left hand click defines the central freuency and the narrow band
        unit
      - +/- 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|DSB  can be used to define the processing mode of
    the selected correlator unit. There is no practical  difference  between
    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  channels
    suffer  from  the Gibbs effect. This mode is therefore not optimized for
    spectroscopic studies. Choosing between an SSB or DSB mode  is  possible
    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).   De-
    fault  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.