Please, can anyone share the design of a STO unit that is PD-able?
Or is it enough to select the PD option for whatever unit we design?
The last PD STO I made was with a gauss turret. The PD checkbox quadruples the fire control tracking speed at the expense of range if I recall correctly, so the basic way to make a PD STO would be to design and research a gauss cannon (or meson or laser), then design and research a turret for that weapon whose tracking speed should be about 4x your racial tracking speed, then select point defence when you design the unit in the ground forces window.
Thank you, Supernovy.
I’ve done a fast test, using a “Triple 30cm C10 Soft X-ray Laser Turret”, with a range of 1,440,000 km and a tracking speed of 60,000 km/s: when it is included in a STO unit, the range decreases to 400,000 km and the TS to my Racial Tracking Speed (6,250 km/s); while if the PD option is on, the range goes to 100,000 km, and the TS rises to 25,000 km/s… not exactly what I expected, but I go with it. 
Just for info, à 30cm laser is generally considered à main gun, it’s really not going to be ideal as a PD weapon in most cases. In particular it’s going to be really big for the volume of PD shots brought to bear and will have a slow reload rate. Not a problem against reduced rate launchers but if your colony is ever attacked by something with small, full size/high reload rate launchers then you won’t be able to intercept every salvo, since your guns will not be ready to fire.
Ideally, you want to use either turretted gauss cannons for close-in point défense or smaller lasers to defend against laser warheads (though I haven’t seen a NPR using those myself yet).
But with these two the important thing you’re getting compared to 30cm lasers is volume of PD fire per ton and per cost. It’s going to be much, much more efficient than using main guns for the job.
Thank you, GrandNord.
I considered only the capacitor value, that is the same for all my recent lasers, and not read the ROF, that indeed is much shorter for smaller calibers.
OP is asking about STO’s not ship PD. So range doesn’t actually matter. Can’t hit a planet with a Laser Warhead that STO PD doesn’t get a shot at.
OP: Turreted STO’s is the only way to get full “bonuses” to tracking, and since mass doesn’t really matter…
10cm laser is enough for PD work, range is determined by wavelength tech, not aperture size.