We have a new guide up by Ryysa, detailing the wonderful world of Electronic Warfare, specifically the use of ECM modules. Excerpt:

As you probably noticed, jammers now also have an optimal range and a falloff range (both of which can be increased by skills, but more to that later on).
The falloff works pretty much the same as the falloff of the guns.
For example: Let's say you have an optimal range of 100km and a falloff range of 30km on your jammer. This means that at a range of 130km your jammer will only hit 50% of the time. At 160+ km it will not hit at all....

Be sure to check it out.