Thanks for your comment.
The MFC is a bit short ranged as the missile is the improved version of the first version of the missile, I will effectively improved it later.
About the active sensor, I thought I had to increase it to follow target out of the planetary range of my sensor during if he runs for the jump point which are far away from earth. Isn't it a good idea?
That's not necessary for targeting purposes. If the target leaves either your FC range or Active Scanner range your missiles will lose their lock and fail to hit their target.
That said having a larger Active Scanner range can still be helpful for other purposes. Maybe you still want to be able to see the enemy even if you can't shoot them (although at most tech levels this can be better accomplished with a thermal sensor) or you want to have your tempting target of a sensor ship much farther away from your enemies than your fighting ships are. This is especially tempting for Gunboats like you have designed. At their small size the enemy may not be able to see them at their firing range. So they may just see your sensor ship and not even know your other ships are there until the missiles start hitting them.