OK after about 9 hours of testing and fooling with these settings I
think I know this much. this is for a radar (the F15R) set for pulse doppler
"speed above" seems to be a velocity filter, the lower you set it the slower the target aircraft can fly and still show up in a head on attack, when set to 24 an aircraft coming at you at 200kts doesnt show up(the piloted plane is moving at 400kts and the closure rate seems to mean nothing at all to these settings)
The only other thing I noticed for sure is that if you set the "minimum range" to 25(and apparently ONLY 25) then an aircraft flying slow enough to not show up on RARAR will "burn through" about 5 miles away, other wise they never show.
One nice thing I noticed is that RCS seems to mean nothing to the settings, I tested at first with other F-15s with an RCS set to 100, then began adding and mixxing in other aircraft such as SU-27 with an RCS of 80 and a B-52 with an RCS of 200, all at different altitudes and speeds, and speed makes a MUCH larger difference to these settings than the alt(unlike what the "help" files would lead you to believe).
The bad things are that, once you've got a lock with a weapon , then you got your lock even if the plane falls off your RADAR(this was with AMRAAMS, SARH missles may have a problem). Also, in combat it tends to make no differance because once engaged of course the enemy turns toward you so the "notching" effect never comes into play except while searching for aircraft.
If you use these settings "speed above-24, speed below-10,minimum range-25, with aspect and look down set to 0, you'll get head on attacks above 200kts will show (but not below, makes huntin helos VERY tough LOL) angled flights will show, but crossing or "beaming" aircraft will dissapear as they cross your nose, up untill they are 20 miles or so away.
If you play with the "aspect" numbers you can get a plane to dissapear as it comes at you but re-appear as it turns and runs away(unfortunatly this is EXACTLY the wrong thing for a doppler RADAR).
I aint done with this yet (plus I got some cool RWR/LOCK and explosion sounds LOL) but I have a feeling this doppler stuff will be more frustration than benifit.