As explained by Jester2138, in HAS mode no range information about the enemy SAM is available.
The AGM-88 locks on to the enemy radar emitter and upon launch simply goes after the emitting signal in a more or less ballistic trajectory.
For the ballistic trajectory, the range of the AGM-88 mainly depends on it's launch altitude and angle, the aircraft speed (M) and the missile speed (M_missile).
The higher and faster the aircraft flies, the higher the range of the missile will be.
In DCS, the AGM-88 appears to be modeled as a missile in the Mach 2 regime (M_missile=2,0).
The graph below is a simple estimation of the maximum ballistic range of the AGM-88, depending on the launch altitude and two exemplary aircraft flight speeds (M=0,9 and M=1,3).
No LOFT mode is considered here, just a simple horizontal launch.
At altitude (>30000ft) a maximum range of 25nm or more should be possible, which is sufficient to keep out of the missile range of medium range SAM systems like an SA-11.
However, its probably not a good idea to go up against a long range SAM system like an S-300.
Happy SEADing!
