CRDBW is used in the main schedule when using either CRDFREQ or CRDDOP to set frequencies on the VLBA for the legacy system that are different from what is set for the RDBE. This is mainly to allow Doppler setting for masers for reference pointing, which is recommended at 86 GHz. See CRDFREQ for more details.
The channels should correspond to the channels in the current setup file because configuration information like the IF, first LO, sideband, etc will be taken from the setup. Only 8 channels will actually get used as, when the RDBE is in use, for bookkeeping ease, only one channel will be assigned to each bbc.
This parameter is equivalent to BW, but is only for use when using the RDBE but wanting different settings in the old system. It will be ignored except on the VLBA using the RDBE.
Any unset values will be set to the same as the first channel. It is good practice to set to 0.D0 when not in use, which may require setting all channels explicitly.