ASDIC display
According to the observations of Grand Admiral, the escort escort of the British often consisted of not the newest ships, distinguished by weak protection and not the most advanced sonar. Therefore, the Germans decided to attack escort ships at night and from a surface position, in which the ASDIC could not locate submarines at a sufficient distance. And the night well hid the Germans sticking out the felling from observers both from the air and from ships. And the tactics of Doenitz gave abundant fruits - boats of the U series with impunity sent more and more new ships to the bottom with enviable regularity.
One of the episodes of the Battle of the Atlantic
Any war is very similar to a chess game - every move of the enemy forces the opposing side to look for reciprocal steps. And the UK responded by installing Mark I-type special anti-submarine radars on ships and planes of the Coast Guard. In particular, the Bristol Beaufighter Mk IF two-seater heavy fighter aircraft was the first aircraft in the world to be equipped with the 270 kg locator version. But this radar was not entirely suitable for detecting a submarine on the surface, and at the beginning of 1941, it was replaced by the Mark II. This equipment has already allowed to “look out” for the protruding wheelhouse at a distance of 13 km, but there were difficulties with it too. The fact is that at night the plane could not go on the bombing of a German submarine, since the interference from the sea surface masked the location of the submarine. The plane had to fly at altitudes that did not exceed 850 meters, otherwise radar signals reflected from the water lit up the screens. But such a technique did play its part - the Germans diminished their speed in the attacks, and the losses of the British Navy decreased, especially within the range of the Coast Command.
Bristol Beaufighter Mk IF - the world's first winged radar carrier
From that moment on, the German submariners receive a response - a massive attack on convoys of the "wolf pack" from all sides. Moreover, the Germans began to do this far from the coast of Britain, which excluded the detection of aircraft with their ubiquitous locators. Then the Americans got it too - in May and June, the Nazis sank 1942 of the Yankee merchant ships around 200.
The answer was not long in coming. On the heavy and long-range aircraft of the Consolidated B-24 Liberator type, the allies installed new radars operating at 1-2 GHz frequencies, as well as powerful searchlights Leigh Light.
Leigh Light under the wing of the B-24 Liberator
The latter made it possible to illuminate a German submarine that surfaced for attack with a beam from a distance of 1,5 km, which greatly simplified the attack on it. As a result, the German U-boats went down much faster and more fun. In the fight against such British tricks on German submarines, locator detectors of the FuMB1942 Methox model appeared in mid-1, later FuMB9 Wanze and FuMB10 Borkum, developed too late by FuMB7 Naxos, and so on until the very end of the war. The Germans only changed the operating range of the received radio emission and sensitivity. It is noteworthy that the Germans borrowed the receivers for Metox ready-made from the warehouses of the French company. The only thing that had to be invented was the receiving antennas, which were built in haste around the wooden cross, for which they received the nickname "Cross of Biscay." Early detection of radiation was the key advantage of such receivers. aviation locators of British forces. As soon as the submarine commander received a signal from Metox (or later versions), he immediately urgently submerged the boat under water. And all this happened before the detection of boats by aircraft radars.
FuMB1 Metox control equipment
The British decided to fight Metox in a simple and proven way - by changing the frequency and length of the radio wave of the locator. At the beginning of the 1943 of the year, the Mark III with a frequency of 3 GHz with a wavelength of 10, appeared. Now the planes could fly to an unsuspecting submarine, which, for example, surfaced to recharge the batteries. Metox was silent in such a situation. And the Germans in this stories at first seriously missed the assumptions about the reasons for the discovery of U-boats. The surviving commanders said that they did not hear the alarm from Metox before the night raid, but for some reason the engineers did not listen to the sailors. Instead, they decided that the British were looking for submarines on ... thermal radiation from diesel engines! As a result, they spent a lot of time and money on the equipment of thermal insulation of the motor compartments of submarines. On the submarines installed special heat shields, which yielded nothing, except for reducing the speed of the underwater vessels. Naturally, nothing sensible came out of this action, and in May-June 1943, the Germans lost about a hundred submarines. The insight to the Germans came after parts of the H2S radar (magnetron lamp) were found on a downed British aircraft in Rotterdam. In the end, all the forces threw on the development of a new radar receiver with a wavelength of 10 cm.
The Germans tried to mislead "flying radar" with the help of balloons, which were left hanging at an altitude of 10 meters above the sea. Such traps under the code name Bold were equipped with steel cables to reflect the signals of the Allied radar and were attached to the drifting buoys. But their effectiveness was expectedly low — the Bold had a significantly lower dispersion area than the submarine, which was easily recorded on the radar screen. Snorkel, which embarked on many German submarines at the end of the 1943 of the year, was an unexpected way out - it could be used to recharge batteries by simply sticking it out of the water. The Germans even covered them with a special radio-absorbing material - here the locators were almost powerless. When the submarines began to be equipped with FuMB7 Naxos, capable of effectively determining the exposure of 10 radar radars, it was too late - the Germans lost the submarines too much.
But not only with the help of locators were hunting for “wolf packs” Dozen. To communicate with large German land, submarines were forced to surface, determine their coordinates and radiate to the command or neighboring vessels. This is where they were directed by forces fleet allies, passed the coordinates to the hunters and drowned the Germans. Typically, a group of hunters included a couple of destroyers or frigates, which left little chance for the enemy. To avoid such losses, the Germans gained know-how - “syringe” transmissions, which were pre-recorded in accelerated form, and then transmitted in just a fraction of a second. At the receiving station, one had only to slow down the recording of the radiogram.
Automatic radio finder Huff-Duff and his antenna on a warship
The answer was the automatic radio finder Huff-Duff, sharpened to intercept and determine the bearing of such "rapid-fire" radio programs. They were put both on the ships and on the coastal posts, which simplified triangulation. This became another modest stud in the coffin cover of the German kriegsmarine.
In general, according to the results of the war, it can be stated that the German command of the Air Force and Navy often neglected electronic intelligence. Meanwhile, regular interception of electromagnetic radiation in the sky of Britain would tell the Germans a lot about the intricacies of war.
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