This parameter is equivalent to FREQ, 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. The main use will be for 86 GHz observations using the PFB personality of the RDBE. With the PFB, the bandwidth per channel can only be 32 MHz and the frequencies are not flexible. To reference point on masers, it is necessary to use the legacy BBCs with narrower bandwidths and with frequencies that are not closely related to the main setup frequencies. Such settings can be determined from Doppler calculatoins using CRDDOP or set explicitly using CRDFREQ. Note that CRDBW must also be set if either of these options is used.
When CRDFREQ or CRDDOP is used, the resulting frequencies appear in the xxcrd.ss files that control the VLBA legacy system. They do not appear in the VEX file. As of this writing, they also don't appear on the summary file, although changes can trigger specification of a new setup group that may not obviously be different from another group, if the only change is in the setup parameters.
Any unset values of CRDFREQ will be set to the same as the first channel' value. It is good practice to set to 0.D0 when not in use, which may require setting all channels explicitly.
It is expected that this capability will be retired when the new control system takes over antenna pointing. At that time, any projects requiring reference pointing on masers will need to use the DDC personality of the RDBE, which allows fine tuning and narrow bandwidths.