I was thinking about building several small active sensors, with different resolutions for small med and large ships instead of one large active sensor.
The idea is size one sensors, with a resolution at 2, 60, and 120. maybe larger sizes for dedicated sensor ships SWAKs or whatnots. I wonder however how effective this would be, will trying to cover the size gaps with a number of smaller and therefore shorter range active sensors be more a hinderence than a larger sensor with some weakness? what about going with two sensors, one larger with say a 100 resolution and one smaller with the 2 resolution
The changes Steve made a few releases ago play pretty heavily against this idea, unless the ratio of resolutions is really big (like in your second example). The issue is that the max range only goes up like sqrt(Resolution), but the range penalty for too big a resolution goes like Resolution^2. So if you've got a resolution that's just right for a particular target, making the resolution 4x larger will cut the range you can detect that target by a factory of 4^(3/2) = 8! (sqrt(4) improvement for bigger resolution/4^2 harm for too big resolution).
This leads to the following comments:
1) Let's say you've got a resolution R sensor of size S. You're
never better off (modulo redundancy/research cost arguments) if you add a sensor of the same size and resolution less than or equal to 4R instead of just doubling the size of the orginal sensor. The reason is that doubling the size doubles the range; in order for the second sensor to compete it needs at least 2x the range, which means it needs 4x the resolution (since range goes like sqrt(R)). From a practical point of view, this means you probably need a resolution of at least ~10R to make it worthwhile - otherwise the benefit of longer range vs. small targets will outweigh the reduction in range vs. large targets.
2) This means you should never build a resolution 2 sensor (actually, you should never build one with resolution <=4). The reason is that resolution 1 sensors are special - they're what you use to see missiles. There's nothing at resolution 2 you might want to shoot at (unless someone's built a fighter that's all engine, or a ridiculously large missile).
3) The other magic size is R=20, since that's the largest size of ship that doesn't require a bridge. A LOT of FAC will be this size. And R=20x1 is bigger than R=10x1. So far in my fleet this game I've got R=1 and R=20 sensors. I've debated adding an R=200, but there are lots of ships out there that come in around 6ktons, so that would only notice the really big ones (plus I've already got pretty good range with my R=20 sensors). One might want to go with R=15 or so (to pick up smaller FAC designs) instead of R=20, but even then unless and until you find a threat will really big ships that you want to see a loooong way away, making an R150-R200 is iffy in my opinion.
So the upshot is that you've got the right idea, you just need to tune the resolutions some.
John