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134-578: During the Handelskrieg (German war on trade) Allied ships travelled independently prior to the introduction of the convoy system and were vulnerable to attacks by U-boats operating as 'lone wolves'. By gathering up merchant ships into convoys the British Admiralty denied them targets and presented a more defensible front if found and attacked. The logical remedy for the U-boat Arm

268-471: A directional antenna transmits radio waves in a beam in a particular direction, or receives waves from only one direction. Radio waves travel at the speed of light in vacuum and at slightly lower velocity in air. The other types of electromagnetic waves besides radio waves, infrared , visible light , ultraviolet , X-rays and gamma rays , can also carry information and be used for communication. The wide use of radio waves for telecommunication

402-418: A microphone , a video signal representing moving images from a video camera , or a digital signal consisting of a sequence of bits representing binary data from a computer. The modulation signal is applied to a radio transmitter . In the transmitter, an electronic oscillator generates an alternating current oscillating at a radio frequency , called the carrier wave because it serves to generate

536-497: A radar screen . Doppler radar can measure a moving object's velocity, by measuring the change in frequency of the return radio waves due to the Doppler effect . Radar sets mainly use high frequencies in the microwave bands, because these frequencies create strong reflections from objects the size of vehicles and can be focused into narrow beams with compact antennas. Parabolic (dish) antennas are widely used. In most radars

670-632: A transmitter connected to an antenna which radiates oscillating electrical energy, often characterized as a wave . They can be received by other antennas connected to a radio receiver ; this is the fundamental principle of radio communication. In addition to communication, radio is used for radar , radio navigation , remote control , remote sensing , and other applications. In radio communication , used in radio and television broadcasting , cell phones, two-way radios , wireless networking , and satellite communication , among numerous other uses, radio waves are used to carry information across space from

804-474: A " push to talk " button on their radio which switches off the receiver and switches on the transmitter. Or the radio link may be full duplex , a bidirectional link using two radio channels so both people can talk at the same time, as in a cell phone. One way, unidirectional radio transmission is called simplex . This is radio communication between a spacecraft and an Earth-based ground station, or another spacecraft. Communication with spacecraft involves

938-803: A "shock effect". Though the Germans had only 21 submarines available, not all of which were operational, they were now primarily based at Ostend in Belgium, giving the submarines better access to the sea lanes around England. In January, before the declaration of "unrestricted submarine warfare" as the submarine blockade was called, 43,550 tonnes of shipping had been sunk by U-boats. The number of sinkings then steadily increased, with 168,200 tonnes going down in August. Attacking sometimes without warning, German U-boats sank nearly 100,000 GRT per month, an average of 1.9 ships daily. The economic and military effect

1072-627: A Service Regulation specifying that "Radiotelegrams shall show in the preamble that the service is 'Radio ' ". The switch to radio in place of wireless took place slowly and unevenly in the English-speaking world. Lee de Forest helped popularize the new word in the United States—in early 1907, he founded the DeForest Radio Telephone Company, and his letter in the 22 June 1907 Electrical World about

1206-550: A chute at the stern of the ship. The first success was the sinking of U-68 off County Kerry , Ireland, on 22 March 1916 by the Q-ship Farnborough . Germany became aware of the depth charge following unsuccessful attacks on U-67 on 15 April 1916, and U-69 on 20 April. UC-19 and UB-29 were the only other submarines sunk by depth charges during 1916. In 1916 the German Navy again tried to use

1340-412: A controller device control the actions of a remote device. The existence of radio waves was first proven by German physicist Heinrich Hertz on 11 November 1886. In the mid-1890s, building on techniques physicists were using to study electromagnetic waves, Italian physicist Guglielmo Marconi developed the first apparatus for long-distance radio communication, sending a wireless Morse Code message to

1474-402: A convoy (waiting for the cover of night to attack). Some sources refer to different wolfpacks by name or provide lists of named wolfpacks, though this can be a misnomer. Donitz’s pack tactic envisaged a patrol line of six to ten boats (later, twenty to thirty or more) across a convoy route to search for targets. If a convoy was found the boats would form a pack, to mount a simultaneous attack. At

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1608-487: A convoy and alerted the BdU . A Rudel (pack) consisted of as many U-boats as could reach the scene of the attack. With the exception of the orders given by the BdU , U-boat commanders could attack as they saw fit. Often they were given a probable number of U-boats that would arrive and when they were in contact with the convoy, make call signs to see how many had arrived. If their number were sufficiently high compared to

1742-597: A device called the High Frequency Direction Finder (HF/DF or Huff-Duff ), which allowed Allied naval forces to determine the location of the enemy boats transmitting and attack them. The pack tactic was able to bring about a force concentration against a convoy but no tactics for co-ordinated attack were developed; each commander present was left to move against the convoy as he saw fit. The escort groups developed group tactics against U-boat attack, gaining an advantage. As packs got larger

1876-474: A favorable impact on US public opinion. She made a second equally successful voyage in autumn of that year. Her sister, Bremen , was less fortunate; she disappeared on her maiden voyage, the cause of her loss unknown. Radio Radio is the technology of communicating using radio waves . Radio waves are electromagnetic waves of frequency between 3  hertz (Hz) and 300  gigahertz (GHz). They are generated by an electronic device called

2010-421: A given bandwidth than analog modulation , by using data compression algorithms, which reduce redundancy in the data to be sent, and more efficient modulation. Other reasons for the transition is that digital modulation has greater noise immunity than analog, digital signal processing chips have more power and flexibility than analog circuits, and a wide variety of types of information can be transmitted using

2144-548: A government license, such as the general radiotelephone operator license in the US, obtained by taking a test demonstrating adequate technical and legal knowledge of safe radio operation. Exceptions to the above rules allow the unlicensed operation by the public of low power short-range transmitters in consumer products such as cell phones, cordless phones , wireless devices , walkie-talkies , citizens band radios , wireless microphones , garage door openers , and baby monitors . In

2278-440: A huge expenditure of effort and material, but met with little success for the time being. Though eventually mines would be one of the most common causes of U-boat loss, only two U-boats were sunk by these measures in 1915. In 1917 Britain and in 1918 America also adopted dazzle camouflage to attempt to reduce shipping losses to torpedoes. The results in both cases were inconclusive. The biggest obstacle to early German efforts

2412-440: A large and expensive armored warship with one torpedo , they needed to be in position before an attack took place. Their fastest speed, while surfaced, of around 15 knots, was less than the cruising speed of most warships and only two-thirds that of the most modern dreadnoughts. Their chief advantage was to submerge, because surface ships had no means to detect a submarine underwater, and no means to attack. However, while submerged,

2546-587: A large economic cost, but it can also be life-threatening (for example, in the case of interference with emergency communications or air traffic control ). To prevent interference between different users, the emission of radio waves is strictly regulated by national laws, coordinated by an international body, the International Telecommunication Union (ITU), which allocates bands in the radio spectrum for different uses. Radio transmitters must be licensed by governments, under

2680-595: A metal conductor called an antenna . As they travel farther from the transmitting antenna, radio waves spread out so their signal strength ( intensity in watts per square meter) decreases (see Inverse-square law ), so radio transmissions can only be received within a limited range of the transmitter, the distance depending on the transmitter power, the antenna radiation pattern , receiver sensitivity, background noise level, and presence of obstructions between transmitter and receiver . An omnidirectional antenna transmits or receives radio waves in all directions, while

2814-427: A more limited information-carrying capacity and so work best with audio signals (speech and music), and the sound quality can be degraded by radio noise from natural and artificial sources. The shortwave bands have a greater potential range but are more subject to interference by distant stations and varying atmospheric conditions that affect reception. In the very high frequency band, greater than 30 megahertz,

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2948-710: A named group formed and mounted a pack attack on a convoy, referring to it by name as a wolfpack is appropriate. In the Pacific the United States Navy (USN) used individual patrol and pack tactics; the South West Pacific command (SoWePac) under Rear-Admiral Ralph Christie , based at Brisbane and Fremantle favoured the individual patrol, while the Central Pacific command, under Rear Admiral Charles Lockwood at Pearl Harbor (SubPac) used

3082-470: A primitive spark-gap transmitter . Experiments by Hertz and physicists Jagadish Chandra Bose , Oliver Lodge , Lord Rayleigh , and Augusto Righi , among others, showed that radio waves like light demonstrated reflection, refraction , diffraction , polarization , standing waves , and traveled at the same speed as light, confirming that both light and radio waves were electromagnetic waves, differing only in frequency. In 1895, Guglielmo Marconi developed

3216-420: A public audience. Analog audio is the earliest form of radio broadcast. AM broadcasting began around 1920. FM broadcasting was introduced in the late 1930s with improved fidelity . A broadcast radio receiver is called a radio . Most radios can receive both AM and FM. Television broadcasting is the transmission of moving images by radio, which consist of sequences of still images, which are displayed on

3350-459: A radio signal is usually concentrated in narrow frequency bands called sidebands ( SB ) just above and below the carrier frequency. The width in hertz of the frequency range that the radio signal occupies, the highest frequency minus the lowest frequency, is called its bandwidth ( BW ). For any given signal-to-noise ratio , an amount of bandwidth can carry the same amount of information ( data rate in bits per second) regardless of where in

3484-661: A range of arguments. This only exacerbated the massive outrage in Britain and America. US President Woodrow Wilson refused to overreact, though some believed the massive loss of life caused by the sinking of Lusitania required a firm response from the US. When Germany began its U-boat campaign against Britain, Wilson had warned that the US would hold the German government strictly accountable for any violations of American rights. Backed by State Department second-in-command Robert Lansing , Wilson made his position clear in three notes to

3618-489: A receiver that is typically colocated with the transmitter. In radio navigation systems such as GPS and VOR , a mobile navigation instrument receives radio signals from multiple navigational radio beacons whose position is known, and by precisely measuring the arrival time of the radio waves the receiver can calculate its position on Earth. In wireless radio remote control devices like drones , garage door openers , and keyless entry systems , radio signals transmitted from

3752-533: A recipient over a kilometer away in 1895, and the first transatlantic signal on 12 December 1901. The first commercial radio broadcast was transmitted on 2 November 1920, when the live returns of the Harding-Cox presidential election were broadcast by Westinghouse Electric and Manufacturing Company in Pittsburgh, under the call sign KDKA . The emission of radio waves is regulated by law, coordinated by

3886-673: A reference to the radiotelegraph and radiotelegraphy . The use of radio as a standalone word dates back to at least 30 December 1904, when instructions issued by the British Post Office for transmitting telegrams specified that "The word 'Radio'... is sent in the Service Instructions." This practice was universally adopted, and the word "radio" introduced internationally, by the 1906 Berlin Radiotelegraphic Convention, which included

4020-446: A screen on a television receiver (a "television" or TV) along with a synchronized audio (sound) channel. Television ( video ) signals occupy a wider bandwidth than broadcast radio ( audio ) signals. Analog television , the original television technology, required 6 MHz, so the television frequency bands are divided into 6 MHz channels, now called "RF channels". The current television standard, introduced beginning in 2006,

4154-589: A shortage of workers to complete U-boats for service in home waters, but it seemed justified by the successes in the Mediterranean in November, when 44 ships were sunk, for a total of 155,882 tons. The total in December fell to 17 ships (73,741 tons) which was still over half the total tonnage sunk in all theaters of operation at the time. In November 1915, U-38 caused a diplomatic incident when she sank

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4288-479: A single torpedo which struck the liner aft, and she sank within 10 minutes, with the loss of 44 passengers and crew, 3 of whom were American. Following speculation that the US would sever relations with Germany, on 28 August the Chancellor issued new orders to submarine commanders and relayed them to Washington. The new orders stated that until further notice, all passenger ships could only be sunk after warning and

4422-441: A smaller bandwidth than the old analog channels, saving scarce radio spectrum space. Therefore, each of the 6 MHz analog RF channels now carries up to 7 DTV channels – these are called "virtual channels". Digital television receivers have different behavior in the presence of poor reception or noise than analog television, called the " digital cliff " effect. Unlike analog television, in which increasingly poor reception causes

4556-416: A television (video) signal has a greater data rate than an audio signal . The radio spectrum , the total range of radio frequencies that can be used for communication in a given area, is a limited resource. Each radio transmission occupies a portion of the total bandwidth available. Radio bandwidth is regarded as an economic good which has a monetary cost and is in increasing demand. In some parts of

4690-402: A total of 63,848 tons. It was decided the same month that further reinforcements were called for, and the large U-boat, U-38 sailed for Cattaro. Since Germany was not yet at war with Italy, even though Austria was, German U-boats were ordered to refrain from attacking Italian shipping in the eastern Mediterranean. When operating in the west, up to the line of Cape Matapan , German U-boats flew

4824-400: A transmitter to a receiver, by modulating the radio signal (impressing an information signal on the radio wave by varying some aspect of the wave) in the transmitter. In radar, used to locate and track objects like aircraft, ships, spacecraft and missiles, a beam of radio waves emitted by a radar transmitter reflects off the target object, and the reflected waves reveal the object's location to

4958-652: A transmitter to control the actions of a device at a remote location. Remote control systems may also include telemetry channels in the other direction, used to transmit real-time information on the state of the device back to the control station. Uncrewed spacecraft are an example of remote-controlled machines, controlled by commands transmitted by satellite ground stations . Most handheld remote controls used to control consumer electronics products like televisions or DVD players actually operate by infrared light rather than radio waves, so are not examples of radio remote control. A security concern with remote control systems

5092-435: A variety of license classes depending on use, and are restricted to certain frequencies and power levels. In some classes, such as radio and television broadcasting stations, the transmitter is given a unique identifier consisting of a string of letters and numbers called a call sign , which must be used in all transmissions. In order to adjust, maintain, or internally repair radiotelephone transmitters, individuals must hold

5226-680: A warship traveling in this manner. Overall, the German Navy was unable to erode the Grand Fleet's advantage as hoped. In the two main surface actions of this period, the U-boat was unable to have any effect, and the High Seas Fleet was unable to draw the Grand Fleet into a U-boat trap. The first attacks on merchant ships had started in October 1914. At that time there was no plan for a concerted U-boat offensive against Allied trade. It

5360-413: Is amplified in the transmitter and applied to a transmitting antenna which radiates the energy as radio waves. The radio waves carry the information to the receiver location. At the receiver, the radio wave induces a tiny oscillating voltage in the receiving antenna which is a weaker replica of the current in the transmitting antenna. This voltage is applied to the radio receiver , which amplifies

5494-703: Is spoofing , in which an unauthorized person transmits an imitation of the control signal to take control of the device. Examples of radio remote control: Radio jamming is the deliberate radiation of radio signals designed to interfere with the reception of other radio signals. Jamming devices are called "signal suppressors" or "interference generators" or just jammers. During wartime, militaries use jamming to interfere with enemies' tactical radio communication. Since radio waves can pass beyond national borders, some totalitarian countries which practice censorship use jamming to prevent their citizens from listening to broadcasts from radio stations in other countries. Jamming

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5628-445: Is a digital format called high-definition television (HDTV), which transmits pictures at higher resolution, typically 1080 pixels high by 1920 pixels wide, at a rate of 25 or 30 frames per second. Digital television (DTV) transmission systems, which replaced older analog television in a transition beginning in 2006, use image compression and high-efficiency digital modulation such as OFDM and 8VSB to transmit HDTV video within

5762-433: Is an audio transceiver , a receiver and transmitter in the same device, used for bidirectional person-to-person voice communication with other users with similar radios. An older term for this mode of communication is radiotelephony . The radio link may be half-duplex , as in a walkie-talkie , using a single radio channel in which only one radio can transmit at a time, so different users take turns talking, pressing

5896-410: Is called "tuning". The oscillating radio signal from the desired station causes the tuned circuit to resonate , oscillate in sympathy, and it passes the signal on to the rest of the receiver. Radio signals at other frequencies are blocked by the tuned circuit and not passed on. A modulated radio wave, carrying an information signal, occupies a range of frequencies . The information ( modulation ) in

6030-427: Is called an uplink , while a link that transmits data from the spacecraft to the ground is called a downlink. Radar is a radiolocation method used to locate and track aircraft, spacecraft, missiles, ships, vehicles, and also to map weather patterns and terrain. A radar set consists of a transmitter and receiver. The transmitter emits a narrow beam of radio waves which is swept around the surrounding space. When

6164-565: Is in radio clocks and watches, which include an automated receiver that periodically (usually weekly) receives and decodes the time signal and resets the watch's internal quartz clock to the correct time, thus allowing a small watch or desk clock to have the same accuracy as an atomic clock. Government time stations are declining in number because GPS satellites and the Internet Network Time Protocol (NTP) provide equally accurate time standards. A two-way radio

6298-417: Is mainly due to their desirable propagation properties stemming from their longer wavelength. In radio communication systems, information is carried across space using radio waves. At the sending end, the information to be sent is converted by some type of transducer to a time-varying electrical signal called the modulation signal. The modulation signal may be an audio signal representing sound from

6432-524: Is the one-way transmission of information from a transmitter to receivers belonging to a public audience. Since the radio waves become weaker with distance, a broadcasting station can only be received within a limited distance of its transmitter. Systems that broadcast from satellites can generally be received over an entire country or continent. Older terrestrial radio and television are paid for by commercial advertising or governments. In subscription systems like satellite television and satellite radio

6566-788: The Atlantic and the Mediterranean , and to a lesser degree in both the Far East and South East Asia , and the Indian Ocean . However, the Allies were able to keep a fairly constant tonnage of shipping available, due to a combination of ship construction and countermeasures, particularly the introduction of convoys . In August 1914, a flotilla of ten U-boats sailed from their base in Heligoland to attack Royal Navy warships in

6700-560: The German Naval Command ; a significant proportion of British imports passed through it, it was critical to French and Italian trade, and submarines would be able to operate effectively in it even in autumn and winter when poor weather hampered Atlantic and North Sea operations. Additionally, there were certain choke points through which shipping had to pass, such as the Suez Canal , Malta, Crete , and Gibraltar . Finally,

6834-595: The International Telecommunication Union (ITU), which allocates frequency bands in the radio spectrum for various uses. The word radio is derived from the Latin word radius , meaning "spoke of a wheel, beam of light, ray". It was first applied to communications in 1881 when, at the suggestion of French scientist Ernest Mercadier  [ fr ] , Alexander Graham Bell adopted radiophone (meaning "radiated sound") as an alternate name for his photophone optical transmission system. Following Hertz's discovery of

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6968-645: The North Sea in the first submarine war patrol in history. Their aim was to sink capital ships of the British Grand Fleet, and so to reduce the Grand Fleet's numerical superiority over the German High Seas Fleet. The first sortie was not a success. One of SM  U-9 's engines broke down and she had to return to Heligoland. Only one attack was carried out, when U-15 fired a torpedo (which missed) at HMS  Monarch . Two of

7102-504: The ionosphere without refraction , and at microwave frequencies the high-gain antennas needed to focus the radio energy into a narrow beam pointed at the receiver are small and take up a minimum of space in a satellite. Portions of the UHF , L , C , S , k u and k a band are allocated for space communication. A radio link that transmits data from the Earth's surface to a spacecraft

7236-400: The radio spectrum into 12 bands, each beginning at a wavelength which is a power of ten (10 ) metres, with corresponding frequency of 3 times a power of ten, and each covering a decade of frequency or wavelength. Each of these bands has a traditional name: It can be seen that the bandwidth , the range of frequencies, contained in each band is not equal but increases exponentially as

7370-531: The 1920s with the introduction of broadcasting. Electromagnetic waves were predicted by James Clerk Maxwell in his 1873 theory of electromagnetism , now called Maxwell's equations , who proposed that a coupled oscillating electric field and magnetic field could travel through space as a wave, and proposed that light consisted of electromagnetic waves of short wavelength . On 11 November 1886, German physicist Heinrich Hertz , attempting to confirm Maxwell's theory, first observed radio waves he generated using

7504-486: The Allies developed counter-measures. The expansion of the escort force, and the development of well-trained and well-organized escort groups, led to more and more successes as the campaign went on. Time and again escort groups were able to fight off numerically superior packs and destroy attackers, until the rate of exchange became ruinous. Effective air cover from long-range aircraft with radar, and escort carriers and blimps , allowed U-boats to be spotted as they shadowed

7638-644: The Austrian flag, and a sinking without warning policy was adopted, since large merchant ships could be attacked on the suspicion of being transports or auxiliary cruisers. The German Admiralty also decided that the Type UB II submarine would be ideal for Mediterranean service. Since these were too large to be shipped in sections by rail to Pola like the Type UB I, the materials for their construction and German workers to assemble them were sent instead. This meant

7772-525: The British) or risk striking a growing array of minefields. While the word "blockade" was avoided in official pronouncements, this amounted to unprecedented restrictions on trade with the Central Powers, with even food considered "absolute contraband of war". Though at this point Germany was still receiving sufficient imports from neutral countries, Germans regarded this as a blatant attempt to starve

7906-716: The Caribbean, were conducted by U-boats on individual patrol, until the introduction of a convoy system there saw the U-boats withdraw to easier hunting grounds. In the South Atlantic and the Indian Ocean individual routing by the Allies and small numbers of U-boats active there again saw the employment of the lone wolf approach by the U-boat Arm. Although the wolfpacks proved a serious threat to Allied shipping,

8040-474: The Earth's atmosphere has less of an effect on the range of signals, and line-of-sight propagation becomes the principal mode. These higher frequencies permit the great bandwidth required for television broadcasting. Since natural and artificial noise sources are less present at these frequencies, high-quality audio transmission is possible, using frequency modulation . Radio broadcasting means transmission of audio (sound) to radio receivers belonging to

8174-605: The English Channel, laying 12 mines off Boulogne, one of which sank the steamship William Dawson the same day. UC-5 laid 6 more mines off Boulogne and Folkestone on 7 September, one of which sank the cable layer Monarch . Further mines were laid off the southeast coast by UC-1 , UC-3 , UC-6 , and UC-7 . On 19 August 1915, U-24 sank the White Star liner SS  Arabic , outward bound for America, 50 mi (80 km) south of Kinsale . He fired

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8308-437: The German government issued on 13 May, 9 June, and 21 July. The first note affirmed the right of Americans to travel as passengers on merchant ships of any nationality. As the Germans claimed it was impossible to use submarines "without an inevitable violation of many sacred principles of justice and humanity", it called for the Germans to abandon submarine warfare against commercial vessels, whatever flag they sailed under. In

8442-623: The German people into submission and wanted to retaliate in kind, and in fact the severity of the British blockade did not go over well in America either. This gave the Germans the pretext to act. The German Chancellor, Theobald von Bethmann Hollweg , felt that such a submarine blockade, based on "shoot without warning", would simply antagonise the United States and other neutrals and have little chance of achieving its objectives. However, he

8576-539: The German public, as by early 1915, all the combatants had lost the illusion that the war could be won quickly, and began to consider harsher measures in order to gain an advantage. The British, with their overwhelming sea power, had established a naval blockade of Germany immediately on the outbreak of war in August 1914, and in early November 1914 declared the North Sea to be a "Military Area". Any ships entering were advised to pass through specific lanes (inspected by

8710-527: The Germans became aware of these tactics, successes were much less common. Efforts were made to use nets to find submerged U-boats, and explosive sweeps to destroy them, but these were largely failures. Attempts were also made to close routes like the Straits of Dover with boom nets and minefields, the so-called Dover Barrage ; to lay minefields around U-boat bases, and station submarines on patrol to catch them leaving or entering port. These measures required

8844-576: The Germans were now bound to the strategy to avoid political embarrassment. The measure was subject to fierce internal debate amongst the German government as neutral nations and the Kaiser reacted strongly negatively, and a compromise was put in place whereby neutral shipping (which the admiralty wished to attack as well) would be spared. In a February 12 directive, von Pohl's replacement as Admiralty Chief Gustav Bachmann however noted that enemy passenger vessels should be deliberately targeted, so as to create

8978-737: The Italian steamer SS  Ancona while sailing under the Austrian flag, and the loss of nine American citizens caused the "sinking without warning" policy to be suspended in April 1916 until the resumption of unrestricted submarine warfare in 1917. A similar incident in March 1916 became a contributing factor in Italy's decision to declare war on Germany in August 1916. Allied countermeasures during this period had mixed success. The navy advised merchant vessels on evading U-boats: to zig-zig, to keep away from

9112-459: The Mediterranean offered the advantage that fewer ships of neutral powers (such as the US or Brazil) would be encountered. Throughout the summer, the German navy assembled a force of 4 U-boats at Cattaro for operations against commerce in the Mediterranean. The campaign got underway in October 1915, when U-33 and U-39 , followed later by U-35 , were ordered to attack the approaches to Salonika and Kavalla . That month, 18 ships were sunk, for

9246-486: The Royal Navy due to the waters being very busy, and was blamed initially on neutral fishing boats. However, on 2 July the small coaster Cottingham accidentally ran down the small coastal U-boat UC-2 off Great Yarmouth , and when she was salvaged she was found to be a submarine minelayer, fitted with twelve mines in six launching chutes. On 21 August UC-5 became the first submarine minelayer to penetrate into

9380-667: The U-boat campaign in the Mediterranean comprised the actions by the Austro-Hungarian Navy 's U-boat force against the French, who were blockading the Straits of Otranto . At the start of hostilities, the Austro-Hungarian Navy had seven U-boats in commission; five operational, two training; all were of the coastal type, with limited range and endurance, suitable for operation in the Adriatic. However during

9514-418: The U-boat was virtually blind and immobile, as early submarines had limited underwater speed and endurance. The U-boats scored a number of impressive successes early in the war, but warships adopted tactics to counter them. Whilst warships were traveling at speed and on an erratic zigzag course they were relatively safe, and for the remainder of the war, the U-boats were unable to mount a successful attack on

9648-429: The U-boats to erode the Grand Fleet's numerical superiority; they staged operations to lure the Grand Fleet into a U-boat trap. Because the U-boats were much slower than the battle fleet, these operations required U-boat patrol lines to be set up in advance; then the battle fleet manoeuvred to draw the Grand Fleet onto them. Several of these operations were staged, in March and April 1916, but with no success. Ironically,

9782-596: The US, these fall under Part 15 of the Federal Communications Commission (FCC) regulations. Many of these devices use the ISM bands , a series of frequency bands throughout the radio spectrum reserved for unlicensed use. Although they can be operated without a license, like all radio equipment these devices generally must be type-approved before the sale. Below are some of the most important uses of radio, organized by function. Broadcasting

9916-405: The air simultaneously without interfering with each other because each transmitter's radio waves oscillate at a different rate, in other words, each transmitter has a different frequency , measured in hertz (Hz), kilohertz (kHz), megahertz (MHz) or gigahertz (GHz). The receiving antenna typically picks up the radio signals of many transmitters. The receiver uses tuned circuits to select

10050-483: The battle away from the ground chosen by his enemy, and forcing any U-boats present to surface if they intended to follow. During 1916 the commerce war continued in the Mediterranean, albeit under cruiser rules after April 24 due to the Sussex incident . Allied countermeasures were largely ineffective; the complex arrangements for co-operation between the various navies meant a fragmented and unco-ordinated response, while

10184-414: The beam strikes a target object, radio waves are reflected back to the receiver. The direction of the beam reveals the object's location. Since radio waves travel at a constant speed close to the speed of light , by measuring the brief time delay between the outgoing pulse and the received "echo", the range to the target can be calculated. The targets are often displayed graphically on a map display called

10318-620: The commander in the HQ boat would co-ordinate the attack. This proved easier to propose than to carry out and proved disastrous when tried. In May 1918 six U-boats under the command of KL Rucker, in U-103 , were operating in the English Channel ; U-103 made contact with a troop convoy but was rammed and sunk by the troopship Olympic before she could attack. U-70 found convoy HS 38 but managed only one torpedo attack, which missed. UB 72

10452-668: The continuous waves which were needed for audio modulation , so radio was used for person-to-person commercial, diplomatic and military text messaging. Starting around 1908 industrial countries built worldwide networks of powerful transoceanic transmitters to exchange telegram traffic between continents and communicate with their colonies and naval fleets. During World War I the development of continuous wave radio transmitters, rectifying electrolytic, and crystal radio receiver detectors enabled amplitude modulation (AM) radiotelephony to be achieved by Reginald Fessenden and others, allowing audio to be transmitted. On 2 November 1920,

10586-877: The convoy attack was unsuccessful, while three U-boats were lost in the operation. A second attempt the following month also failed. A further attempt in June 1940 following the Norwegian campaign ( Rösing's wolfpack ) also failed, leading to a re-think of German tactics. The revised approach saw Dönitz micromanaging operations at sea from his headquarters in occupied France, relying on the supposedly unbreakable Enigma code to transmit and receive orders and co-ordinate movements. U-boat movements were controlled by U-boat Command ( BdU ) from Kerneval. U-boats usually patrolled separately, often strung out in lines across likely convoy routes to engage merchant ships and small vulnerable destroyers, being ordered to congregate only after one located

10720-466: The customer pays a monthly fee. In these systems, the radio signal is encrypted and can only be decrypted by the receiver, which is controlled by the company and can be deactivated if the customer does not pay. Broadcasting uses several parts of the radio spectrum, depending on the type of signals transmitted and the desired target audience. Longwave and medium wave signals can give reliable coverage of areas several hundred kilometers across, but have

10854-464: The death of Leon C. Thrasher , drowned when U-28 sank Falaba on 28 March 1915. On 7 May 1915, the liner RMS  Lusitania was torpedoed by U-20 , 13 mi (21 km) off the Old Head of Kinsale , Ireland, and sank in just 18 minutes. Of the 1,960 people aboard, 1,197 were killed, 124 of them US citizens. Following the incident, the German government attempted to justify it with

10988-482: The effect that the US would regard any subsequent sinkings that harm American citizens as "deliberately unfriendly", but signaling an acceptance of submarine warfare under cruiser rules. While the American public and leadership were not ready for war, a rule on what is acceptable and what is not had been set as a result of the sinking. The appearance of new minefields off the east coast of Britain in June 1915 puzzled

11122-408: The end of June 1915, the Germans had assembled a further three prefabricated Type UB I submarines at Pola, two of which were to be transferred to the Austro-Hungarian Navy. They were also assembling three Type UC I minelaying submarines, which were ordered converted into transports to carry small quantities of critical supplies to Turkey. The Mediterranean was an attractive theater of operations to

11256-510: The event of a full-scale war, fleet operations. The USN deploys its attack submarines on individual patrols, with the exception of one or (rarely) two attack submarines in each carrier strike group . American ballistic missile submarines have always operated alone, while Soviet ballistic missile submarines operated in well-protected bastions . To date the world's navies continue to deploy their submarines on individual patrols. Handelskrieg The U-boat campaign from 1914 to 1918

11390-570: The existence of radio waves in 1886, the term Hertzian waves was initially used for this radiation. The first practical radio communication systems, developed by Marconi in 1894–1895, transmitted telegraph signals by radio waves, so radio communication was first called wireless telegraphy . Up until about 1910 the term wireless telegraphy also included a variety of other experimental systems for transmitting telegraph signals without wires, including electrostatic induction , electromagnetic induction and aquatic and earth conduction , so there

11524-460: The expected threat of the escorts, they would attack. This led to a series of successful pack attacks on Allied convoys in the latter half of 1940 (known as " the Happy Time " to the U-boat men). While the German pack tactic was effective, it had several drawbacks. Most notably, wolfpacks required extensive radio communication to coordinate the attacks. This left the U-boats vulnerable to

11658-413: The first commercial radio broadcast was transmitted by Westinghouse Electric and Manufacturing Company in Pittsburgh, under the call sign KDKA featuring live coverage of the Harding-Cox presidential election . Radio waves are radiated by electric charges undergoing acceleration . They are generated artificially by time-varying electric currents , consisting of electrons flowing back and forth in

11792-592: The first radio communication system, using a spark-gap transmitter to send Morse code over long distances. By December 1901, he had transmitted across the Atlantic Ocean. Marconi and Karl Ferdinand Braun shared the 1909 Nobel Prize in Physics "for their contributions to the development of wireless telegraphy". During radio's first two decades, called the radiotelegraphy era, the primitive radio transmitters could only transmit pulses of radio waves, not

11926-618: The frequency increases; each band contains ten times the bandwidth of the preceding band. The term "tremendously low frequency" (TLF) has been used for wavelengths from 1–3 Hz (300,000–100,000 km), though the term has not been defined by the ITU. The airwaves are a resource shared by many users. Two radio transmitters in the same area that attempt to transmit on the same frequency will interfere with each other, causing garbled reception, so neither transmission may be received clearly. Interference with radio transmissions can not only have

12060-467: The group Shark , Seadragon , and Blackfish were "Blakely's Behemoths". Wolfpacks fell out of use during the Cold War as the role of the submarine changed. With trade returned to peacetime conditions and the end of convoying, the submarine ceased to be a commerce raider and moved to a range of more traditional military roles, such as scouting, intelligence-gathering, clandestine transport and in

12194-443: The highest scoring commander of all, Lothar von Arnauld de la Perière . In 1916 the Germans completed two submarine merchant vessels , to be used as blockade runners . The aim was to use them to carry high value goods to neutral nations such as the US, which still maintained a strict neutrality, and was prepared to trade with Germany as with any other nation. The first of these vessels, Deutschland , sailed in summer 1916 and made

12328-488: The hunting tactics of wolves and submarines were known by their nickname of graue Wölfe (grey wolves). With the outbreak of the Second World War the U-boat Arm found the success of the pre-war trials had created some complacency; when these tactics were first tried in October 1939 ( Hartmann's wolfpack ) they were a failure; Hartmann found he was unable to exercise any tactical control from his boat at sea and

12462-513: The last day of the year SM  U-24 sank the pre-dreadnought battleship Formidable . By the end of the initial campaign, the U-boats had sunk nine warships while losing five of their own number. Due to fears of submarine attack, the Grand Fleet spent much of the first year dispersed on the West coast, while their home base at Scapa Flow had defenses installed. The initial phase of

12596-402: The longest transmission distances of any radio links, up to billions of kilometers for interplanetary spacecraft . In order to receive the weak signals from distant spacecraft, satellite ground stations use large parabolic "dish" antennas up to 25 metres (82 ft) in diameter and extremely sensitive receivers. High frequencies in the microwave band are used, since microwaves pass through

12730-533: The main remedy favored by the Allies for the U-boat menace, the Otranto Barrage , was of little value. Just two U-boats were caught in the barrage in all the time it was in operation; meanwhile merchant shipping suffered huge losses. In 1916 the Allies lost 415 ships, of 1,045,058 GRT, half of all Allied ships sunk in all theatres. Eight of the top dozen U-boat aces served in the Pola flotilla, including

12864-517: The major fleet action which did take place, the Battle of Jutland , in May 1916, saw no U-boat involvement at all; the fleets met and engaged largely by chance, and there were no U-boat patrols anywhere near the battle area. A further series of operations, in August and October 1916, were similarly unfruitful, and the strategy was abandoned in favor of resuming commerce warfare. The British were well aware of

12998-473: The misuse of neutral flags, it may not always be possible to prevent attacks on enemy ships from harming neutral ships. (3) Navigation to the north of Shetland, in the eastern parts of the North Sea and through a zone at least thirty nautical miles wide along the Dutch coast is not exposed to danger. Von Pohl breached protocol by acting without proper consultation with the Kaiser and the other naval offices, but

13132-472: The need for legal restrictions warned that "Radio chaos will certainly be the result until such stringent regulation is enforced." The United States Navy would also play a role. Although its translation of the 1906 Berlin Convention used the terms wireless telegraph and wireless telegram , by 1912 it began to promote the use of radio instead. The term started to become preferred by the general public in

13266-450: The next step was arming ships for the purpose of seeking out and engaging the U-boats in gun battles; two U-boats were sunk in 1915 whilst attacking trawlers so fitted. The following step was to arm and man ships with hidden guns to bait in submarines, the so-called Q ship . A variant on the idea was to equip small vessels with a submarine escort. In 1915, two U-boats were sunk by Q-ships, and two more by submarines accompanying trawlers. Once

13400-577: The other hand, serious offence had been given to neutrals such as Norway and the Netherlands, and brought the United States to the brink of war. This failure, and the various restrictions imposed on the U-boat Arm in the Atlantic area largely brought the campaign there to a halt, although it continued with little hindrance in the Mediterranean and elsewhere, where there was less likelihood of offending neutrals. The depth charge, or "dropping mine" as it

13534-566: The outbreak of the Second World War Germany had had 27 sea- and ocean-going U-boats, enough to mount a single patrol line in the Atlantic. Patrol lines were not named and if a pack was formed it was referred to by the name of the skipper who had found the target. This situation improved with the fall of France and the occupation of the French Atlantic ports but U-boat construction had barely kept pace with losses and it

13668-453: The pack tactic. American wolfpacks, called coordinated attack groups , usually comprised three boats that patrolled in close company and organized before they left port under the command of the senior captain of the three. "Swede" Momsen devised the tactics and led the first American wolfpack – composed of Cero , Shad and Grayback – from Midway on 1 October 1943. In this way the USN

13802-505: The picture quality to gradually degrade, in digital television picture quality is not affected by poor reception until, at a certain point, the receiver stops working and the screen goes black. Government standard frequency and time signal services operate time radio stations which continuously broadcast extremely accurate time signals produced by atomic clocks , as a reference to synchronize other clocks. Examples are BPC , DCF77 , JJY , MSF , RTZ , TDF , WWV , and YVTO . One use

13936-451: The radio frequency spectrum it is located, so bandwidth is a measure of information-carrying capacity . The bandwidth required by a radio transmission depends on the data rate of the information (modulation signal) being sent, and the spectral efficiency of the modulation method used; how much data it can transmit in each kilohertz of bandwidth. Different types of information signals carried by radio have different data rates. For example,

14070-409: The radio signal desired out of all the signals picked up by the antenna and reject the others. A tuned circuit (also called resonant circuit or tank circuit) acts like a resonator , similar to a tuning fork . It has a natural resonant frequency at which it oscillates. The resonant frequency of the receiver's tuned circuit is adjusted by the user to the frequency of the desired radio station; this

14204-451: The radio spectrum, the right to use a frequency band or even a single radio channel is bought and sold for millions of dollars. So there is an incentive to employ technology to minimize the bandwidth used by radio services. A slow transition from analog to digital radio transmission technologies began in the late 1990s. Part of the reason for this is that digital modulation can often transmit more information (a greater data rate) in

14338-456: The radio waves that carry the information through the air. The modulation signal is used to modulate the carrier, varying some aspect of the carrier wave, impressing the information in the modulation signal onto the carrier. Different radio systems use different modulation methods: Many other types of modulation are also used. In some types, a carrier wave is not transmitted but just one or both modulation sidebands . The modulated carrier

14472-426: The risk of U-boat traps to the Grand Fleet, although they had no means of knowing where these might lie. However Jellicoe had developed a tactical response to the problem (which, in the event, was never tested). Faced with a German fleet that turned away, he would assume a submarine trap, and decline to follow, but would move at high speed to the flank, before deploying or opening fire; the aim of this would be to fight

14606-428: The risks from this lack of co-ordination increased, such as overlapping attacks, collision or friendly fire incidents (in May 1943 for example, two U-boats stalking a Gibraltar convoy, U-439 and U-659 collided, with the loss of both). Away from the Atlantic, the U-boat Arm had less scope for pack attacks; Operation Drumbeat against US shipping in early 1942, off the US eastern coast, and Operation Neuland in

14740-481: The same digital modulation. Because it is a fixed resource which is in demand by an increasing number of users, the radio spectrum has become increasingly congested in recent decades, and the need to use it more effectively is driving many additional radio innovations such as trunked radio systems , spread spectrum (ultra-wideband) transmission, frequency reuse , dynamic spectrum management , frequency pooling, and cognitive radio . The ITU arbitrarily divides

14874-720: The saving of passengers and crews. On September 1 the unrestricted submarine warfare doctrine was essentially abandoned. This proved unacceptable to the Naval High Command, and on 18 September the High Seas flotillas were withdrawn from the commerce war. The German Navy sent their first submarines to the Mediterranean in response to the Anglo-French Dardanelles campaign , after it became obvious that their Austro-Hungarian allies could do little against it with their small submarine force, which nevertheless

15008-513: The second note Wilson rejected German defenses, rebutting some false claims and asserting that all that mattered was that the Lusitania did not defend herself, but was attacked without warning in such a way that endangered innocent civilian lives. Secretary of State William Jennings Bryan considered Wilson's second note too provocative and resigned in protest after failing to have it moderated. The third note, of 21 July, issued an ultimatum, to

15142-420: The shore, to turn away and run from spotted submarines if possible, or to turn towards submarines in front of them to force them to submerge. A system of defensively armed merchant ships were also employed with stern mounted guns to discourage pursuit by U-boats operating on the surface. Such defensive measures were the most effective. Offensive measures were less effective. From arming ships for self-defence,

15276-414: The ten U-boats were lost. Later in the month, the U-boats achieved success, when U-21 sank the cruiser HMS  Pathfinder . In September, SM  U-9 sank three armoured cruisers ( Aboukir , Hogue , and Cressy ) in a single action. Other successes followed. In October U-9 sank the cruiser Hawke and U-27 sank the submarine E3 , the first time one submarine sank another, and on

15410-431: The transmitting antenna also serves as the receiving antenna; this is called a monostatic radar . A radar which uses separate transmitting and receiving antennas is called a bistatic radar . Radiolocation is a generic term covering a variety of techniques that use radio waves to find the location of objects, or for navigation. Radio remote control is the use of electronic control signals sent by radio waves from

15544-472: The war new larger U-boats came into service plus Germany shipped several overland. The Austro-Hungarian U-boats had a number of successes. On 21 December 1914 U-12 torpedoed the French battleship  Jean Bart (beyond Otranto), causing her to retire to Malta for serious repairs, and on 27 April 1915 U-5 sank the French cruiser  Léon Gambetta , with a heavy loss of life. While U-boats could sink

15678-475: The war, yet eager to demonstrate a role for itself. Throughout 1914, figures like Hermann Bauer , Alfred von Tirpitz and Hugo von Pohl argued that submarine commerce raiding provided a means of quickly defeating Britain. Perhaps influenced by the appearance of submarines in fiction , naval officials proposed extremely optimistic views of how effective even a very a small U-boat (with as few as 4–20 vessels) blockade could be. Such views were readily taken up by

15812-510: The weak radio signal so it is stronger, then demodulates it, extracting the original modulation signal from the modulated carrier wave. The modulation signal is converted by a transducer back to a human-usable form: an audio signal is converted to sound waves by a loudspeaker or earphones, a video signal is converted to images by a display , while a digital signal is applied to a computer or microprocessor, which interacts with human users. The radio waves from many transmitters pass through

15946-475: The whole of the English Channel, are hereby declared to be a War Zone. From February 18 onwards every enemy merchant vessel encountered in this zone will be destroyed, nor will it always be possible to avert the danger thereby threatened to the crew and passengers. (2) Neutral vessels also will run a risk in the War Zone, because in view of the hazards of sea warfare and the British authorization of January 31 of

16080-663: Was Seewolf , a seven boat operation against the North American coast, countered by the USN with Operation Teardrop . The codename applied to the group or to the patrol line that they formed. Not all groups so named were involved in pack tactics; the Goeben group was formed to enter the Mediterranean and support operations there; Eisbär group were dispatched to the waters off South Africa, where they operated independently. Of those groups forming patrol lines not all found convoys or were able to form packs if they did. Where

16214-490: Was a need for a more precise term referring exclusively to electromagnetic radiation. The French physicist Édouard Branly , who in 1890 developed the radio wave detecting coherer , called it in French a radio-conducteur . The radio- prefix was later used to form additional descriptive compound and hyphenated words, especially in Europe. For example, in early 1898 the British publication The Practical Engineer included

16348-439: Was able to make command at sea work; by forming stable groups of three submarines, these groups were able to develop group tactics for attack on Japanese convoys. Part of this development, and to promote an esprit de corps , was naming the groups as they formed. These names were based on that of the group commander; the group comprising Growler (Cdr. "Ben" Oakley), Sealion and Pampanito were known as "Ben's Busters";

16482-408: Was caught on the surface by British submarine D4 , torpedoed and sunk. During the period of operation, 19 homeward and 11 outward convoys passed through the patrol area without loss and two U-boats (a third of the force) had been destroyed. In October 1918 another attempt at a co-ordinated attack was made in the Mediterranean, when two U-boats attempted a co-ordinated attack on a convoy. One of them

16616-595: Was however, virtually nothing. Britain alone had around 20 million GRT in shipping at the start of the war and production managed to keep pace with losses. On 10 April 1915 the British steamer Harpalyce , a Belgian relief ship and clearly marked as such, was torpedoed without warning by SM  UB-4 near the North Hinder lightship, just outside the strip of sea declared safe by von Pohl. The ship had been en route for America to collect food for starving Belgians, and its sinking outraged US citizens already unhappy at

16750-808: Was initially named, was first mooted in 1910, and developed into practicality when the British Royal Navy's Commander in Chief, Admiral of the Fleet Sir George Callaghan , requested its production in 1914. Design work was carried out by Herbert Taylor at HMS Vernon Torpedo and Mine School in Portsmouth , England, and the first effective depth charge, the "Type D", became available in January 1916. Anti-submarine vessels initially carried only two depth charges, to be released from

16884-615: Was not until the summer of 1941 that several patrol groups were possible, creating the need to differentiate them. At first this was by location (West, Centre, South, Greenland) but in August BdU began to assign codenames, chosen for their historical or cultural value. This continued until the end of the campaign, though after the spring of 1944 the UbW had moved away from pack attacks to its inshore campaign of individual patrols operating in British coastal waters. The last named U-boat group

17018-457: Was recognised that the U-boat had several drawbacks as a commerce raider, and such a campaign risked alienating neutral opinion. In the six months to the opening of the commerce war in February 1915, U-boats had sunk 19 ships, totalling 43,000  GRT . Because Germany could not possibly deal with British naval strength on an even basis, the German navy was relatively inactive at the start of

17152-514: Was simply the small size of the submarine fleet relative to their task. At the beginning of this period the British Merchant Marine had a shipping fleet totaling of 21 million GRT . In six months of unrestricted submarine warfare U-boats sank 3 ⁄ 4  million tons of Allied shipping, scarcely denting the British merchant fleet; whilst new building, and additions from ships seized, had more than made up this loss. On

17286-598: Was successful in defending the Adriatic . The first U-boats sent, U-21 and the two small coastal boats, UB-7 and UB-8 , achieved initial success, U-21 sinking the Royal Navy pre-dreadnought battleships HMS  Triumph and HMS  Majestic on 25 and 27 May, respectively, on her way to Constantinople, but ran into severe limitations in the Dardanelles, where swarms of small craft and extensive anti-submarine netting and booms restricted their movements. By

17420-486: Was sunk and its commander, ObLt Karl Dönitz , was taken prisoner. During the interwar years the German Navy was forbidden to have U-boats but began to re-arm in 1935. Under Karl Dönitz as FdU developed co-ordinated attack tactics based on Bauer's plan and his own experience and trials of the new tactics in 1936 proved successful. Dönitz called his strategy of submarine warfare Rudeltaktik , which literally translates as " pack tactic" but referred specifically to

17554-628: Was superior in numbers and could operate on most of the world's oceans because of the British Empire , whereas the Imperial German Navy surface fleet was mainly restricted to the German Bight , and used commerce raiders and submarine warfare to operate elsewhere. German U-boats sank almost 5,000 ships with over 12 million gross register tonnage , losing 178 boats and about 5,000 men in combat. U-boats operated in

17688-726: Was the World War I naval campaign fought by German U-boats against the trade routes of the Allies , largely in the seas around the British Isles and in the Mediterranean , as part of a mutual blockade between the German Empire and the United Kingdom . Both Germany and Britain relied on food and fertilizer imports to feed their populations, and raw materials to supply their war industry. The British Royal Navy

17822-735: Was to gather U-boats similarly into attacking formations. In early 1917 Hermann Bauer , the Commander of the High Seas U-boats ( Führer der Unterseeboote [FdU]) proposed establishing patrol lines of U-boats across convoy routes, in order to mass for attack on any convoy reported. These boats would be supported by a forward base on land and a headquarters and supply vessel, such as the Deutschland -class converted U-cruisers equipped with radio and supplies of fuel and torpedoes. The shore station would monitor radio transmissions and

17956-646: Was unable to hold back the pressures for taking such a step. The Chancellor and the Admiralty came to an agreement on 1 February and directives were sent out the next day. On 4 February 1915 Admiral Hugo von Pohl , commander of the German High Seas Fleet and Head of the Admiralty Staff until 1 Feb, published a warning in the Deutscher Reichsanzeiger (Imperial German Gazette): (1) The waters around Great Britain and Ireland, including

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