Wideband Observing

by stephanw — last modified Dec 05, 2013 by Gustaaf Van Moorsel

The wideband observing setups provide the widest possible bandwidth for a given observing band, with channel spacing depending on the number of polarization products.

Wideband & Subarray Correlator Options(all but L band)

Polarization products Channel spacing
Full (RR, RL, LR, LL) 2   MHz
Dual (RR, LL) 1   MHz
Single (RR or LL) 0.5 MHz

8-bit wideband setups are available for all observing bands, providing a total of 2 GHz of bandwidth per polarization (1 GHz per polarization at L-band).  3-bit setups are available for all bands above S-band, providing total bandwidths per polarization of 4 GHz (C/X bands), 6 GHz (Ku band), or 8 GHz (K/Ka/Q bands). In all cases but L band each of the subbands is 128 MHz wide (at L band the default is 64 MHz/subband, yielding channels twice as narrow as those listed in the table above). Recent tests suggest use of the 3-bit samplers yields higher continuum sensitivity; see the section on VLA Samplers for details.

In many frequency bands the total processed bandwidth is less than that delivered by the front-end. In those cases the observer may independently tune two 1 GHz baseband pairs when using the 8-bit samplers, or four 2 GHz baseband pairs when using the 3-bit samplers. The (fairly mild) tuning restrictions are described in the section on VLA Frequency Bands and Tunability.