Backends

There are 3 types of spectral line backends which can be individually connected to any receiver.

• The 1 MHz filter bank, consisting of 4 units with 256 MHz each. The units can be connected to different or the same receivers (giving bandwidths between 256 MHz and 1024 MHz, the latter only usable with 230G2). For example, two receivers could use 512 MHz each, or four receivers 256 MHz each, or combinations. Each unit can be shifted by steps of 32 MHz relative to the center frequency of the connected receiver. If all four units are combined to 1024 MHz and connected to 230G2, no other backend can be connected to 230G2.
• The 100 kHz filter bank, consisting of 256 channels of 100 kHz (splittable into two halves movable inside the 500 MHz instantaneous bandwidth, and connectable to two different receivers)
• The autocorrelator: The software treats the autocorrelator as one unit although physically it consists of two identical machines. The following numbers are to be understood for the complete autocorrelator setup. Available resolutions are 10, 20, 40, 80, 320 and 1250 kHz. The bandwidth is between 20 MHz and MHz, depending on resolution. The correlator can be split into 8 independent subbands, each of which can be configured individually and connected to the same or different receivers. For the larger bandwidths (i.e. more than one subband of 80 MHz) usually a problem of platforming exists (i.e. baselines from the different subbands have slightly different levels). This makes the autocorrelator not adequate for observations of broad, weak lines (typically extragalactic sources).