The EVLA can reach many frequencies that the VLA cannot. Such frequencies can be specified to the VLA using the same VLASYNA etc parameters as before, but with values that would be outside the range that would be allowed for the VLA. Since SCHED checks the ranges of these settings, that checking has to be overridden. Setting EVLA to a non-zero value will cause such checking. It is an integer to allow for possible future varients with different values. Note that the VLASYNA etc frequencies must still conform to the patterns like 50*N +- 10.1 MHz. When EVLA is set, the VLAFEAB and VLAFECD parmeters are not checked at all.