[PavelKirilovich]

German radars get a bad rap during WWII for some reason. They had some systems which were quite good by the standards of the time and other systems on par with Allied and Soviet technology. And of course, a few subpar systems. The problem is not so much the technology fitted to the boat, as the platform to which the technology is fitted.

The radar horizon is pretty limited from a U-boat. You've only got the emitter a few metres above the ocean's surface and the emitter is space-constrained, the number of transmit and receive modules that can be fitted to the array is limited by the need to field a compact system. Power aperture and power aperture product is thus limited; but peak power was reasonable. The Germans did pretty well with this set, the key problem is what I mentioned earlier, it's only a few metres above the water.

The reason we see radars and lookouts stationed on the highest points of a ship is to artificially increase the distance to the horizon. It's a trigonometry thing. The higher a radar, the further it can see because geography (earth curvature) doesn't prohibit the signal from propagating back to the receivers. However, the enemy's radar warning receivers and direction finders only need to detect the signal, whereas we need to send a signal out AND get it back. Sod's law applies: the more **** you need to do, the less likely all of it is going to get done.

So what the radar does for you, in effect, is act as a "I'm over here" beacon to enemy ASW efforts. You want to run under full emissions control. Manually check every time you surface to make sure the radar operator/radio operator isn't running the radar of his own initiative. Nothing is more painful than being bounced by a hunter-killer group when your batteries badly needed a recharge and your CO2 levels are dangerously high.

It's OK to ping capitol ships with your sonar. It's not OK to ping ASW vessels with your sonar. Capitol ships are escorted by ASW vessels. The reason it's OK to ping the big gun big tonnage targets is because we don't have good shock dampening systems, sonars weren't typically fitted to large gun combatants because of space constraints and shock damage that would be caused by the gun's recoil to the system. Same reason full broadsides aren't fired: they'll shake the boat apart.