Overview
A ‘zoom’ mode is available for higher resolution spectral line observations. It is designated as NE_107M for ‘narrowband extended’, and has a bandwidth of 107 MHz with 32k channels (with ~13.5 MHz rolloff on either side, giving an effective bandwidth of ~80 MHz – see Figure 1). This gives a channel width of 3.3 kHz or 0.7 km/s at 1.4 GHz. It runs concurrently with the wideband 4k channel correlator mode, providing simultaneous wideband continuum observations. It is being successfully used for the L-band LSPs MHONGOOSE and Fornax.
The NE_54M mode (twice the frequency resolution of NE_107M) is available in shared risk mode at L band. Users interested in this capability should contact SARAO to discuss possible use cases.
Unfortunately the filter response causes 50% of the NE_54M mode band to be lost, giving an effective bandwidth of 27 MHz.
Commissioning results for the 107 MHz narrowband mode
In Figure 3 below we show the results of observations of M83 in both wideband and 107 MHz narrowband mode. The correlator is performing as expected and the expected sensitivity is achieved.
For more details see the commissioning reports from the Large Survey Projects Fornax and MHONGOOSE, which have been conducting extensive observations using this mode since August 2020:
MHONGOOSE commissioning: narrowband observations of NGC 5068