DBBC:

The DBBC being developed for the EVN and many geodesy stations is also a system that samples at 512 or 1024 MHz and digitally filters the signals to the desired bandwidths. But it has a different design where, like with the old BBCs, the frequency can be set flexibly anywhere in the IF band without concern about crossover frequencies etc. The DBBC design has a module for each output baseband, so they are more directly comparable to BBCs. Support for the DDC personality of the DBBC has recently been implemented in SCHED, but should be used with caution. The PFB personality is not yet supported.

The DDC personality is selected by default, and can be selected explicitly by setting the DBE parameter to DBBC_DDC in the setup file. SCHED will also accept a value of DBBC_PFB but this is not properly supported and will simply mimic the PFB personality of the RDBE. There are several different versions of the DBBC being deployed with slightly different components. The major difference is in the patching of IFs (aka conditioning modules) to particular BBCs (this may become fully switchable with future upgrades). Three variants are recognised by SCHED. The variant is specified in the stations file with the DBBCVER parameter. Each conditioning module (IF) has up to 4 switchable inputs. The signal available on each input is station dependent, so IF names (IFNAME, IFCHAN) should be assigned with due reference to the particular station's wiring.

Currently 2 IF filters are supported. One in the range 10-512 MHz and a second in the range 512-1024 MHz. A suite of additional IF filters will be enabled with a future firmware release but are not available yet and so are not yet supported by SCHED. SCHED will warn you if your selected frequencies attempt to use both the 10-512 MHz and 512-1024 filters at the same time.

Baseband filter widths of 1, 2, 4, 8 or 16 MHz are possible. 32 MHz will be enabled with a future firmware upgrade. The frequencies for the band edges in the DDC personality can be set to any multiple of 10 kHz. (There is also a binary tuning mode which allows band edges to be set to a multiple of $1024/2^{31} {\rm MHz} = 0.476 {\rm Hz}$, but its use is not advised and it is not currently supported by SCHED.)

Sampling is done with 2 bits at Nyquist rate only (1 bit sampling can be emulated by channel selection on the recorder).