In spectral-like mode (SET MODE SPECTRAL), the only X variables
allowed are Channel number, IF frequency, RF rest frequency, and Velocity,
while Y variables are the components of the visibilities, or
autocorrelations (SET Y AUTO). SET ANTENNA may be used, but
only with autocorrelations. Some SET keywords
have a different meaning:
SET SUBBAND: here groups linked be the keyword TO indicate concatenation rather than averaging. For instance SET SUBBAND C01 TO C06 will form a single broad band spectrum with the 6 continuum sub-band visibilities; or SET SUBBAND L01 TO L02 will concatenate the first two line sub-bands to form a single spectrum, plotted in a single box.
SET AVERAGING TIME or SCAN or NONE has no meaning; all data in the current index is averaged to form a single spectrum in any case.
Use of SET DROP and SET GIBBS is the same as in time mode, but their effect here is more obvious on the plots since the channels are plotted individually.