The array file contains information applicable to the whole array, mainly time parameters, and includes three card images. The first card image contains time information; the second, the coordinates of the pole; and the third, control information for various devices such as the correlator and de-icers. The third card image is of particular interest to VLBI observers. Columns 1 and 2 specify which subarrays control the correlator and the integration time, respectively. Because the VLA can observe simultaneously in multiple subarrays and because the necessary or desired synthesizer frequencies for continuum, VLBI, spectral-line, and/or 0.33-GHz observations are usually incompatible, a second, complete set of Fluke synthesizers is available. Columns 3-10 on the third card image specify which subarray controls each Fluke synthesizer, with columns 3-6 for Fluke set 1 and Fluke synthesizers A, B, C, and D, and columns 7-10 for Fluke set 2 and Fluke synthesizers AA, BB, CC, and DD. Single-antenna VLBI usually uses Fluke set 2. When more than two subarrays are being used, some will be using Fluke sets controlled by another subarray and observer.
The SUBi file for subarray 
, where 
1, 2, 3, 4, or 5,
contains names of source list files, local oscillator and receiver
settings, and antenna control and calibration parameters. The
parameters for standard VLBI observations are kept in the standard
subarray file called SYSSUB, which the VLA operator copies into
the appropriate subarray file prior to the start of the observations.
SYSSUB includes the default ALIAS, LO, FI, and
DS cards for the VLBI observing bands described in Section
7. The ALIAS cards xxALxx identify the VLBI bands
as variations on the VLA standard continuum bands. The LO cards
(xxLO) specify the values of 
in GHz and 
rounded to the
nearest MHz appropriate for the VLBI observing bands and also point to
the SYSxIF and VLBxROT files. The FIne-tuning cards
(xxFI) include an ``S'' to tell the Modcomp computers to set the A
and B Fluke synthesizers (actually twice the B Fluke synthesizer) to
the values given, and a ``1'' or ``2'' to tell the Modcomp computers
to use Fluke set 1 or 2 for this subarray. By default, the DS or
data-selection card tells the Modcomp computers to use an integration
time of 10 s.
The IF files contain gain calibration and antenna efficiency parameters for each antenna.
The standard SYSxROT files include control parameters for each antenna, such as subreflector rotation and focus, and collimation errors; and control parameters for each frontend. For a VLBI program, the VLA operator uses the standard SYSxROT files to create VLBxROT files that also identify the VLBI reference antenna. Specifying a reference antenna for phased-array VLBI observations is highly recommended, to avoid reference antenna changes that degrade the VLA correlator data in two ways. First, reference antenna changes will introduce phase jumps that are difficult to correct. Second, reference antenna changes will complicate polarization calibration.
The antennas file file contains miscellaneous information about each antenna, including digital communication system (DCS) address, station ID, and the control parameter for over-the-top pointing. Column 45 has the number of the subarray to which the antenna is assigned. A ``T'' in column 57 means exclude this antenna from the analog sum. A ``T'' in column 58 means that during a VLA+PT program, this is the donor antennna to be used for single-antenna VLBI during a concurrent VLBA program.
The baseline file contains the positions of the antenna stations and delay constants.
The pointing file contains the parameters specifying the azimuth and elevation pointing corrections.