An update on what I've discovered. Distance away makes no difference, unless you're out of range of what you are trying to salvage. The Convergence of the beams only happens when they are connected with a secondary system (Salvage Beam + AMC).
Another change (bug) with 0.154, Salvager beams with no secondary weapon system connected can not salvage anything at all. I've tried with 5 ships, online, offline. You get the animation that it's going to salvage, but no blocks are gathered or disappear. Tested on asteroids, non-factioned default stations and pirate ships with overheating cores.