A useful listing of the spectral windows can be obtained with uvlist
% uvlist vis=cx012.SS433.2006sep07.1.miriad options=spectra rest frequency : 92.46875 92.46875 92.46875 92.46875 92.46875 92.46875 starting channel : 1 16 31 46 61 76 number of channels : 15 15 15 15 15 15 starting frequency : 92.46875 93.46875 92.96875 97.53125 96.53125 97.03125 frequency interval : -0.03125 -0.03125 -0.03125 0.03125 0.03125 0.03125 starting velocity : 0.000 -3242.095 -1621.047-16413.105-13171.010-14792.058 ending velocity : 1418.416 -1823.678 -202.631-17831.522-14589.427-16210.474 velocity interval : 101.315 101.315 101.315 -101.315 -101.315 -101.315
where you can see the 3 lower sideband windows and 3 upper sideband windows. Notice the rest frequency in this example appear a little odd, being identical in all windows. See also Section 6.5.3 for a discussion on this. Note that uvlist only displays the first selected frequency setting. If your source and calibrator have a different setup, add select=source() to look at the appropriate setting for each object.