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Overview
A ‘zoom’ mode is Two ‘zoom’ modes, designated NE_107M and NE_54M, are available for higher resolution spectral line observations.
Only one zoom window can be activated. It runs concurrently with the wideband 4k channel correlator mode, providing simultaneous wideband continuum observations.
The filter roll-off has a width of ~13.5 MHz for both modes, thus ~27 MHz of the digitized band is not usable. Please see bandpass response plots below.
The NE_107M mode
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.
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info
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.
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Commissioning results
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In Figure 3 2 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.
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MeerKAT 32k zoom mode commissioning: NGC 1365
The NE_54M mode
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Unfortunately the filter response causes 50% of the NE_54M mode band to be lost, giving an effective bandwidth of 27 MHz. Please see typical bandpass response in Figure 3 below. |
Users interested in observing hydroxyl lines should note that while the 1665- and 1667-MHz lines can be observed simultaneously, the bandpass response is not wide enough to encompass the 1612 MHz line as well. The centre frequency cannot be adjusted during an observation.
