Not a Number, on 06 December 2012 - 10:47 AM, said:
I don't believe ECM actually makes a mech invisible according to the BT rules. It only really affects anything within its range of 180M. Correct me if I'm wrong. If it would also prevent missiles from being tracked all the way to the target – without a TAG countering that – like I and some others suggested, it would still be effective against missile attacks for both the ECM equipped mech its nearby allies inside the bubble.
You are not correct.
In the tabletop by normal game rules, if your opponent does not mount Artemis or NARC or C3 or Beagle, then Guardian ECM does nothing. Nothing at all. Not even a little bit. It *only* counters dedicated electronic warfare equipment. It has no effect on TAG or targeting computers (see Total Warfare page 134, the current iteration of the tabletop rules).
A guidebook for additional rules called Tactical Operations offers additional rules for double-blind games (page 220-224), where it is possible to have unidentified sensor blips and the like. This is closer to what we are using in MWO. Under double-blind rules, if you have line of sight to a target then you can see it and spot it and target it with LRMs and the like, at no penalty, regardless of ECM. Visual spotting range (Mk1 eyeball) is pegged at 1800m under normal daylight conditions, and 900m under light fog or snowfall.
Under double-blind rules, it is possible to get a sensor blip for an enemy unit that is not in anyone's LOS. This is unreliable, but can go out as far as 720m (1080m with a Beagle Active Probe). Hills, but not other kinds of obstruction, block this indirect sensor blips completely. Hills do not block a Beagle Active Probe. Other forms of obstruction make it more difficult to detect things without LOS, even affecting Beagle (Hills don't even slow Beagle down, but trees/buildings make it harder, yes I know it's weird). Under foggy or rainy or dark conditions it is possible to not have LOS to a target even if there are no obstructions in the way, but sensors can be used to find such hidden units anyway.
In double-blind, ECM makes it harder to acquire sensor blips without LOS, but only so long as the spotting unit is within the jamming radius of the ECM suite. If the spotting unit has LOS, then ECM does nothing. If the spotting unit does not have LOS but is outside jamming range (180m), then ECM does nothing.