Chapter 385: Operation Hunger (9)
Submarines, as the core of underwater forces, often engage in dealings and competitions with powerful enemies under the seemingly calm sea surface.
However, this also leads to a very obvious problem.
You must know that seawater is equivalent to a huge conductor with a good electromagnetic shielding effect. Therefore, submarines diving underwater can hardly receive any TV signals, mobile phone signals, wireless network signals, or most military radio communications.
So how can submarines keep in touch with the headquarters? Surface up to receive and send telegrams?
This was a dead end in the late World War II. As long as it surfaced, the submarine had a high probability of being targeted by anti-submarine aircraft.
Therefore, the communication problem of submarines has become a global problem.
At the beginning when submarines became independent combat forces, in order to solve the communication problem of submarines, the navies of some countries used the surface warships escorting submarines as relay information stations. After the radio transmitted the information to the surface warships, the warships sent sound to the underwater through knocking and other means, and received it through the sonar on the submarine. This method was gradually abandoned after World War I because of its high distortion rate and almost no confidentiality.
There is also a method of sending and receiving information through radio buoys, but when using radio buoys, the submarine needs to remain relatively still in the ocean, and then send the buoy connected to the communication equipment on the boat through a wire to the sea surface, and then receive the radio signal through the buoy.
This device solves the problem of submarine communication with the outside world, but it is still subject to great limitations: the submarine needs to remain suspended underwater, so it is easier to be discovered and attacked, which reduces the submarine's survivability. In addition, radio buoys are relatively fragile and may be damaged in harsh environments.
At the end of World War II, communication experts discovered a way for submarines to receive communications underwater: long-wave stations.
Seawater has a strong absorption effect on electromagnetic wave energy, but it is different for electromagnetic waves of different wavelengths. The shorter the wavelength and the higher the frequency, the greater the attenuation in seawater. But electromagnetic waves with longer wavelengths can penetrate a little bit of seawater. The longer the wavelength, the stronger the penetration of electromagnetic waves. The signals sent by very long wave and ultra-long wave radio stations can enter water from tens of meters to more than a hundred meters.
Long-wave radio is a general term. In fact, electromagnetic waves with a wavelength of 1,000 to 10,000 meters are called long waves, electromagnetic waves with a wavelength of 100,000 to 1 million meters are called very long waves, and electromagnetic waves with a wavelength of 1 million to 10 million meters (10,000 kilometers) are called ultra-long waves.
Very long wave radio stations can penetrate more than 20 meters of seawater. At the end of World War II, the German Navy had already begun to develop a very long wave communication system. Submarines do not need to surface and can receive very long wave telegrams sent by the command center at the periscope depth. However, the periscope depth is still not safe enough for submarines.
Ultra-long wave radio stations can penetrate 100 meters of seawater, which is also the navigation depth of submarines in normal combat readiness cruises.
Therefore, the long-wave radio stations that people collectively call are actually the most commonly used very long wave and ultra-long wave radio stations.
But the problem is that building a long-wave radio station is not a small project. How big is the antenna of a long-wave radio station?
It can only be said that it is a very large and huge thing; if you build a tower more than 100 meters high, it is only a small part of the long-wave radio antenna!
The antenna of the long-wave station is too long, so it is not vertical, but "lying horizontally". The role of the iron tower over 100 meters high is to isolate the antenna body from the ground as much as possible to prevent the signal quality from being interfered by ground waves when the long-wave station sends a message.
In 1986, the United States built a long-wave radio station. The radio station consists of two parts, one in Wisconsin and the other in Michigan, 258 kilometers apart. The two parts can work together or separately. The total length of its antenna is 135 kilometers, and there are 8 transmitters, half of which are working and half are standby, with a total power of 28 megawatts.
It takes more than an hour to drive 135 kilometers.
Why is it so long... Because the wavelength of the radio waves sent by the long-wave station is very long; the length of the antenna is generally one-tenth of the integer multiple of the wavelength, and the length of the antenna is closely related to the quality of signal transmission.
Ultra-long-wave radio stations with a wavelength of 1,000 kilometers generally use 1/8 wavelength antennas, which means that the antenna length is... 1000÷8=125 kilometers. It is not impossible to use an antenna with a wavelength of 1/16, but the signal quality will not be that high.
Yannick hesitated again and again before agreeing to build a long-wave radio station.
At this time, all the German submarines cruising in the North Atlantic received telegrams from the Wolf Pack Command.
"Captain! The command called and found prey again."
The captain took the telegram, took a look, and his eyes lit up. "Nearly two hundred transport ships? It's really a big guy." After comparing the distance on the nautical chart, he leaned in front of the periscope to observe the surroundings and gave an order. "Surface! Go full speed!" The location they are now is a little far from the ambush point, and they will definitely not catch up with the underwater navigation.
With waves of shaking, the submarine slowly surfaced, shaking with the waves on the sea, ups and downs.
"Be careful to be alert around!"
A sailor stepped forward to unscrew the hatch of the bridge, and the remaining seawater mixed with the fierce sea breeze poured down, and the people around shuddered suddenly. The temperature inside the submarine is kept above 30 degrees all year round due to the operation of power and mechanical equipment, just like the hot Sahara Desert.
The sailors put on their winter coats, climbed out of the bridge and onto the deck along the ladder, smoking and observing the sea conditions around them.
And the cold sea breeze kept pouring into the submarine, sweeping away the unpleasant smell inside the submarine.
The submarines during World War II did not have the advanced air filtration devices of later generations, and the smell inside was quite unpleasant. The smoke produced by diesel engines, the smell of rotten and spoiled food, the stink in the toilet and the sweat odor of the crew... It is not difficult to understand why cologne is so popular on German U-boats.
"It's so cold!" The two shirtless sailors in the submarine power compartment shuddered suddenly and hurriedly found a piece of clothing to put on.
The high faith and fighting spirit of the officers and soldiers of the German Navy submarine force are the basis for maintaining their high level of self-discipline and mutual trust. In this case, military discipline itself is often not so important. Some German captains who are known for their strict discipline also have a relatively loose standard for the implementation of discipline on the boat.
The combat uniforms of the crew of the German Navy submarine force were originally traditional navy blue uniforms, but they were not comfortable to wear in such a small space as a submarine. Therefore, in the eyes of most German captains, as long as the crew can effectively perform their combat missions and are highly competent, they can choose what they want to wear.