Wideband Observing
The wideband observing setups provide the widest possible bandwidth for a given observing band, with channel spacing depending on the number of polarization products as listed in the following table:
|
Wideband & Subarray Correlator Options (all but P- and L-bands) | |
|---|---|
| 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, and 256 MHz per polarization at P-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 P- and 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, while at P-band the default is 16 MHz/subband, resulting in 125 kHz channel spacing.
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, or choose to have a mix 8-bit and 3-bit samplers. The tuning restrictions are described in the section on VLA Frequency Bands and Tunability, and the 8-bit and 3-bit samplers are described in the section on VLA Samplers.
