Documentation on uvspect

Task: uvspect
Purpose: Analyse uvdata spectra and plot amplitude   phase spectra
Categories: uv analysis, plotting

        UVSPECT is a Miriad task to analyse and plot visibility spectra.
        Plot Amplitude and Phase versus channel, frequency or velocity.
        The default is to average the selected uvdata for all baselines
        and polarizations. UVSPECT does not apply the gains, or bandpass
        corrections when plotting the data.

Key: vis
        The input visibility file. No default.

Key: device
        PGPLOT device (e.g. /retro, plot.plt/im for hardcopy on a Vax,
        or  /sunview, plot/ps for harcopy on a Sun).  No default.
        See documentation on the device keyword for more information.

Key: interval
        Averaging interval in minutes. Default is no averaging.

Key: select
        Standard uvdata selection. Default is all visibilities. See
        documentation on the select keyword for more information.

Key: line
        Line type of the data in the format
          type,nchan,start,width,step
        Here "type" can be `channel', `wide' or `velocity'.
        Default is all channels.

Key: fmode
        Flagging type to plot. Set fmode=a to plot flagged and unflagged
        data. fmode=u to plot unflagged data, fmode=f to plot flagged data.
        Default is to plot all data.

Key: fft
        fft is a character string describing the FFT processing options.
        Default fft=' ' does no FFT processing. Other options take the
        complex FFT for each record and each spectral window before
        averaging the data.
           +	The sign of the exponent in the FFT.
           -	The sign of the exponent in the FFT.
           s	Add a phase gradient of pi per channel before the FFT
        	This produces a half channel shift after the FFT.
           q	Quad swap the input to move the center to the 1st point.
           h	Hanning smooth the output.
        Use fft=-qsh to make frequency spectra from HATCREEK correlator
        lag data with the lsb and usb of LO1 adjacent for each corf.
        The input uvdata must be the default all spectral channels with
        the number of channels in each window being a power of 2.
        Other options to take the FFT of any input line type are possible
        but not yet implemented.

Key: hann
       Hanning smoothing length (an odd integer  15). Is applied after
       averaging over time. Default is no smoothing (hann=1).

Key: xrange
        Plot range in the x-direction (in channels or km/s according to
        the linetype selected). Default	is to self-scale.

Key: amprange
        Plot range for amplitude in the y-direction (in intrinsic units).
        Default is to self-scale.

Key: phirange
        Plot range for phase in the y-direction (in degrees).
        Default is (-180,180) degrees.

Key: mode
        Mode can be 'inter' or 'batch'. Default is inter. In either mode,
        the user is prompted for options after each plot on a non-hardcopy
        device. The options are applied to the current spectrum, which can
        then be replotted. mode=inter displays the cursor. Type the first
        character and  cr  to select option. The cursor handling is device
        dependent, and the character and  cr  may need to given several times.
        Options:
          Device - enter new plot device.
          Limits - change plot limits.
          Channel - change x-axis to channel number in the line keyword.
          Velocity - change x-axis to velocity.
          Frequency - change x-axis to frequency.
          Replot - replot current spectrum.
          Position - display cursor position. (if device supports a cursor)
          Write - write out current spectrum to an ascii file.
          Quit - stop processing and exit from task.
          End - end of options, get next average.
           cr  - go to next time average.
        The original inputs are restored for the next time average.