This section covers the scheduling of wide bandwidth observations. With the older tape and MARK5A systems, that means 512 or 1024 Mbps using or using a large number of "tracks" on disk. With the digital backends (RDBE and DBBC) and newer recording systems (MARK5C for now, maybe X cube or MARK6 later), completely new systems are involved. The first couple of paragraphs below are about the old systems. Then the section goes into more detail about the new digital systems.
With the Mark5A recording system, the maximum bit rate that can normally be recorded is 1024 Mbps on a Mark IV system and 512 Mbps on a VLBA system. These rates are recorded on a single module, unlike in the tape era when 2 drives or 2 heads were required.
SCHED can make schedules for the 512 Mbps and 1Gbps modes. See the examples eg512.key for a VLBA only case and eg2head.key for a PCFS (MarkIV) case. Since the advent of disk recordings, for the user, these modes are not much different from other modes. The VLBA telescope schedules indicate use of the wide band mode simply through the specification of track numbers above 64. Note that the two examples do either only VLBA or only Mark IV, but it is ok to mix them.
New digital backends and a new recording system started to be used for science in 2012. These increase the available bit rate to significantly higher values. The RDBE/Mark5C system developed at Haystack and NRAO records 2048 Mbps. Higher rates may eventually be provided. The DBBC system, developed in Italy and also using the Mark5B or Mark5C recording systems, is being deployed on a similar time scale and has similar bandwidths. Other, even wider bandwidth, recording systems are under development but will not be discussed here yet.