next up previous contents
Next: LINE /FIXED_FREQ Up: PDBI and ALMA language Previous: FREQUENCY   Contents


LINE

        [PDBI\]LINE Name Frequency Band [Lock [Center [Harm]]]

    Define  and  plot the receiver frequency coverage of the Plateau de Bure
    Interferometer (with the receivers installed in winter 2006/2007).   The
    command syntax is identical to that of the corresponding command in OBS:
        Name      is a line name to label the plot
        Frequency is the rest frequency in GHz
        Band      should be USB or LSB
        Lock      is LOW or HIGH [optional, default LOW]
        Center    is the IF1 frequency in MHz [optional, default 6500]
        Harm      is the harmonic number [optional]

    o The receiver band to be used (1 to 4) will be determined by the  soft-
    ware.

    o  Since  2015,  NOEMA observations are preferentially performed using a
    limited number of LO frequencies for which  receiver  performances  have
    been  optimized. Those frequencies are distributed all over the receiver
    bands every 500MHz. For latest states of NOEMA (from 2015 on),  this  is
    taken  into  account  in the ASTRO\LINE command. The command checks that
    the LO frequency is located on this grid. When this is not the case, the
    command  returns  an  error and a new IF center frequency is proposed to
    ensure a tuning frequency that matches the grid.  The option /ONGRID can
    be  used  in  order  to let the command use this suggested frequency and
    avoid to return an error.  The tuning frequency is computed  using  only
    the  source  LSR  velocity.  With the Doppler tracking, the actual LO is
    slightly different from the tuning frequency.  Both tuned and tracked LO
    frequencies  are  given  in output when the LINE command arguments match
    the tuning grid.  With the option /FIXED_FREQ, the command  ignores  the
    tuning grid.

    o The center frequency is expressed in the first IF (4-8 GHz = 4000-8000
    MHz). WARNING: it is highly not recommended to center the line frequency
    at  6 GHz. This is because the correlator analyses quarters of the 4 GHz
    bandwidths, and 6 GHz is very precisely at the limit  between  two  such
    adjacents quarters.

    o  The plot displays the four "quarters" Q1...Q4 that can be selected as
    input for the correlator (see NARROW_INPUT command):
      Q1 = 4.2-5.2 GHz, Q2 = 5.0-6.0 GHz
      Q3 = 6.0-7.0 GHz, Q4 = 6.8-7.8 GHz

    o Commands NARROW and SPECTRAL are available to setup the  IF  processor
    and  the  spectral  units  of the narrow-band correlator (see the corre-
    sponding help). A typical ASTRO session would look like:

    line toto 100 usb           ! choice of rx tuning
    narrow q1 q3                ! choice of the correlator windows
    spectral 1  20 320 /nar 1   ! correlator unit 1
    spectral 2 320 200 /nar 2   ! correlator unit 2
    spectral 2 320 210 /nar 2   ! new def. of unit 2 --> plot is updated

    o Command PLOT can be used to plot the full receiver coverage,  that  of
    the NARROW band correlator, or that or the WIDEX correlator.

    o  LINE  can  also be used to produce plots of the frequency coverage of
    the old receivers (replaced in 2006/2007). The command OBSERVATORY  PDBI
    year allows one to select the instrument as of the selected year:
    - 1995: 3 and 1.3 mm receivers, 500 MHz bandwidth
    - 2000: 3 and 1.3 mm receivers, 580 MHz bandwidth
    - 2006: new generation receivers (NGR: 4 GHz bandwidth, 2 polar.)
    - 2010 NGR +  modifications in the LO system
    - 2013 = 2010 + additional slight modification in the LO system
    - 2015 = 2013 + Optimized tuning on a LO grid [default]
    For  the  OLD  receivers (years 1995 & 2000), the commands NARROW, SPEC-
    TRAL, PLOT are not active. Please enter HELP LINE OLD for a  description
    of the behaviour of the LINE command in that case.


Subsections

Gildas manager 2018-05-25