FREQ specifies the LO sum observing frequencys for the baseband channels in MHz. When not specified, the last value specified is used. If 0 is specified, or FREQ is never given in the schedule, the default from the setup file is used. Any channels not specified will be set to the same frequency as the first. This defaulting only works when that channel was not previously set to an explicity value. The defaulting to the first channel is usually not what is desired. Whenever the frequencies change, a comment appears in the operator schedule file; the appropriate changes are made to the BBC frequencies for antennas using VLBA or VEX control files; and for snap files, dummy video converter commands are written without the correct video converter number and with the full LO sum (personnel at ``snap'' sites must edit in the correct video converter numbers and subtract the first LO). Since both the VLBA and Mark IV systems can only set frequencies to the nearest 10 kHz and the Mark III video converters are often used for Mark II projects, do not try to set a frequency that is not an even 10 kHz. Actually, SCHED will round to this value, or to DOPINCR, if it is given.