The VLA parameters generated using this command are apparently are no longer used as of 2007 or earlier. The capability to specify the parameter has been left in place, but should not be used.
Description for historical interest:
VLAIF gives the name of the VLA IF file that contains gain calibration and efficiency information.
Note that, if any of FLUKEA, FLUKEB, VLAFEAB, VLAFECD, VLASYNA, VLASYNB, VLAIF, FEFILTER, or VLAROT are specified, both LO and FI cards will be made. In such cases, any other parameters allowed to default will be set to the standard value for the specified VLABAND.