11/7/2023 0 Comments Rc mini submarineIf two-way communication is needed, the boat must ascend nearer to the surface and raise an antenna mast to communicate on higher frequencies, usually HF and above.īecause of the narrow bandwidths available, voice transmission is impossible only slow data is supported. Hence, VLF is always one-way, from land to boat. This precludes submarines from transmitting VLF, but a relatively simple antenna (usually a long trailing wire) will suffice for reception. This implies high transmitter powers and very large antennas covering square kilometres. Worse, small antennas (relative to a wavelength) are inherently inefficient. Natural background noise increases as frequency decreases, so a lot of radiated power is required to overcome it. However these depth requirements restrict submarines to short reception periods, and antisubmarine warfare technology may be capable of detecting the sub or antenna buoy at these shallow depths. The buoy rises to a few metres below the surface, and may be small enough to remain undetected by enemy sonar and radar. A deeper vessel can use a buoy equipped with an antenna on a long cable. VLF radio waves (3–30 kHz) can penetrate seawater to a few tens of metres and a submarine at shallow depth can use them to communicate. An underwater telephone sometimes called Gertrude is also used to communicate with submersibles. If a submarine hides near such a device, it can stay in contact with its headquarters. Apparently, both the American ( SOSUS) and the Russian navies have placed sonic communication equipment in the seabed of areas frequently travelled by their submarines and connected it by underwater communications cables to their land stations. Sound travels far in water, and underwater loudspeakers and hydrophones can cover quite a gap. Main article: Underwater acoustic communication Other techniques that have been used include sonar and blue lasers. A few nations have built transmitters which use extremely low frequency (ELF) radio waves, which can penetrate seawater to reach submarines at operating depths, but these require huge antennas. Very low frequency (VLF) radio waves can penetrate seawater just over one hundred feet (30 metres), and many navies use powerful shore VLF transmitters for submarine communications. Transmitting messages to these submarines is an active area of research. In the event of a nuclear war, submerged ballistic missile submarines have to be ordered quickly to launch their missiles. During the Cold War, however, nuclear-powered submarines were developed that could stay submerged for months. Submarines can surface and raise an antenna above the sea level, or float a tethered buoy carrying an antenna, then use ordinary radio transmissions however, this makes them vulnerable to detection by anti-submarine warfare forces.Įarly submarines during World War II mostly travelled on the surface because of their limited underwater speed and endurance, and dove mainly to evade immediate threats or for stealthy approach to their targets. Because radio waves do not travel well through good electrical conductors like salt water, submerged submarines are cut off from radio communication with their command authorities at ordinary radio frequencies.
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