Documentation on uvfft

Task: uvfft
Purpose: Fourier transform a sequence of selected uv-data.
Categories: uv analysis

        UVFFT takes a 1-D Fourier transform of a uv-data sequence. 
        If the sequence is a time series, then the FFT is a fringe
        rate spectrum. If the sequence steps the delay center, then
        the FFT is a bandpass.

Key: vis
        The input UV dataset name. No default.

Key: select
        This selects the data to be processed, using the standard uvselect
        format. Default is all data. Selecting more than one baseline
        does not make much sense.

Key: line
        Standard linetype of data to be tranformed, in the form:
          type,nchan,start,width,step
        where type can be `channel'  `wide' or `velocity'.
        The default is wide,2,1,1,1. The maximum number of channels
        which can be processed is 8.

Key: size
        The length of the sequence for the Fourier transform.
        uv-data points in excess of the size of the transform are omitted.
        Must be a power of 2. The default is 128.

Key: log
        The list output file name. The default is the terminal.

Key: device
        standard PGPLOT device, e.g. /xw

Key: delay
        Step size for stepped delay center. FFT is bandpass function.
        Default=0  Delay center not stepped. FFT is fringe frequency spectrum.