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99-588: The Aichi D3A was the first Japanese aircraft to bomb American targets in the war, commencing with Pearl Harbor and U.S. bases in the Philippines , such as Clark Air Force Base . They sank more Allied warships than any other Axis aircraft. In mid-1936, the Japanese Navy issued the 11-Shi specification for a monoplane carrier-based dive bomber to replace the existing D1A biplane then in service. Aichi , Nakajima , and Mitsubishi all submitted designs, with

198-763: A US Navy sailor killed two civilian workers and wounded another, before shooting himself at the Pearl Harbor Naval Shipyard . On October 14, 1992, the US Environmental Protection Agency added the Pearl Harbor Naval Complex as a superfund to the so-called National Priorities List . 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

297-471: 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

396-418: 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

495-414: A propeller spinner , it became a standard with D3A2. The pilot position was equipped with a Type 95 telescopic gunsight in the earlier models and a Type 99 in the later models, which were used for aiming the bomb during the dive. The observer / navigator position was equipped with a Type 97 Mk1 drift sight , which was a long vertical tube located in the front-left of the observer's seat. In addition,

594-492: 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

693-632: 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

792-474: 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

891-606: 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

990-412: 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

1089-466: A faster diving speed of 240 knots (440 km/h) The second aircraft was extensively modified before delivery to try to address the problems. Power was increased by replacing the Hikari with the 626 kW (839 hp) Mitsubishi Kinsei 3 in a redesigned cowling , and the vertical tail was enlarged to help with the directional instability. The wings were slightly larger in span and the outer sections of

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1188-421: 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

1287-545: 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

1386-572: 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

1485-595: 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

1584-427: 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,

1683-470: 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

1782-420: 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

1881-459: 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

1980-489: 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

2079-521: 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

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2178-644: 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

2277-446: 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,

2376-441: 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

2475-416: 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

2574-466: A token force. During the reign of King Kalākaua the United States was granted exclusive rights to enter Pearl Harbor and to establish "a coaling and repair station". Although this treaty continued in force until August 1898, the U.S. did not fortify Pearl Harbor as a naval base. As it had for 60 years, the shallow entrance constituted a formidable barrier against the use of the deep protected waters of

2673-400: 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

2772-652: 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

2871-435: 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

2970-413: 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

3069-703: 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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3168-445: 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

3267-433: 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

3366-721: Is an American lagoon harbor on the island of Oahu , Hawaii, west of Honolulu . It was often visited by the naval fleet of the United States , before it was acquired from the Hawaiian Kingdom by the U.S. with the signing of the Reciprocity Treaty of 1875 . Much of the harbor and surrounding lands are now a United States Navy deep-water naval base. It is also the headquarters of the United States Pacific Fleet . The U.S. government first obtained exclusive use of

3465-410: 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

3564-427: 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

3663-954: Is currently under restoration at the Planes of Fame Museum in Chino, California . There are two unrestored D3As on display at the National Museum of the Pacific War in Fredericksburg, Texas. In 2022, the Pearl Harbor Aviation Museum began acquiring the remains of a D3A from Papua New Guinea for eventual exhibit. Data from Japanese Aircraft of the Pacific War General characteristics Performance Armament Aircraft of comparable role, configuration, and era Related lists Pearl Harbor Pearl Harbor

3762-553: 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

3861-417: 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

3960-642: Is that the tide of events rushes on to annexation to the United States." From the conclusion of the Civil War , to the purchase of Alaska , to the increased importance of the Pacific states, the projected trade with countries in Asia and the desire for a duty-free market for Hawaiian staples, Hawaiian trade expanded. In 1865, the North Pacific Squadron was formed to embrace the western coast and Hawaii. Lackawanna in

4059-524: 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

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4158-690: The Battle of the Coral Sea , Yorktown at the Battle of Midway and Hornet at the Battle of the Santa Cruz Islands . In addition, they damaged the carrier Enterprise both at the Battle of the Eastern Solomons and at the Battle of the Santa Cruz Islands . Besides carrier-based units, D3A dive bombers also operated from land bases during the Solomon Islands campaign, where they participated in

4257-532: The Guadalcanal Campaign , Operation I-Go , Operation SE and Operation RO, and during the New Guinea campaign , where they participated in the Battle of Milne Bay and Battle of Buna–Gona . The main land-based unit to operate D3A dive bombers during these campaigns and battles was the 2nd/582nd Air Group . During the course of the war, D3A dive bombers often combined their attacks upon enemy warships with

4356-526: The Hawaiians . Puʻuloa was regarded as the home of the shark goddess, Kaʻahupahau, and her brother (or son), Kahiʻuka, in Hawaiian legends. According to tradition, Keaunui , the head of the powerful Ewa chiefs, is credited with cutting a navigable channel near the present Puʻuloa saltworks, by which he made the estuary, known as "Pearl River", accessible to navigation. Making due allowance for legendary amplification,

4455-591: 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

4554-675: The Model 12 . The extra power reduced range, so the design was further modified with additional fuel tanks to bring the total tankage to 900 L (240 US gal), giving it the range needed to fight effectively over the Solomon Islands . Known to the Navy as the Model 22 , it began to replace the Model 11 in front-line units in the autumn of 1942, and most Model 11s were then sent to training units. While some late production models of D3A1 were fitted with

4653-497: The Philippines in 1944, land-based D3A2s took part in the fighting, but were hopelessly outdated and losses were heavy. By then, many D3A1s and D3A2s were operated by training units in Japan, and several were modified with dual controls as Navy Type 99 Bomber Trainer Model 12 s (D3A2-K). During the last year of the war, the D3A2s were pressed back into combat for kamikaze missions. A D3A2

4752-497: 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

4851-632: The leading edges had wash-out to combat the snap rolls, and strengthened dive brakes were fitted. These changes cured all of the problems except the directional instability, and it was enough for the D3A1 to win over the Nakajima D3N 1. In December 1939, the Navy ordered the aircraft as the Navy Type 99 Carrier Bomber Model 11 ( kanjō bakugekiki , usually abbreviated to 艦爆 kanbaku .). The production models featured slightly smaller wings and increased power in

4950-400: 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

5049-531: 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

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5148-592: The D3A1 took part in all major Japanese carrier operations in the first 10 months of the war. They achieved their first major success against the Royal Navy during their Indian Ocean raid in April 1942. D3A1 dive bombers scored over 80% hits with their bombs during attacks on two heavy cruisers and an aircraft carrier during the operation. Before the Indian Ocean raid, the established doctrine regarding attacks against ships

5247-474: 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

5346-652: The IJN Nakajima B5N Kate torpedo bomber; consequently enemy vessels were often sunk by a combination strike of bombs and torpedoes. However, there were occasions when just the D3A's would make the attacks, or at least score the sinking hits. Discounting the Pearl Harbor strike, which also used the B5N for level bombing and torpedo attacks, D3A dive bombers were credited with sinking the following Allied warships (partial list): As

5445-580: The Navy Type 99 dive bomber. Nakajima sent several examples to the 14th Air group operating at Haikou on Hainan island in South China . These D3A1s were commanded by Lieutenant Sadamu Takahashi and supported the Imperial Japanese Army in the capture of Nanning , which was intended to cut the supplies coming from French Indochina . After the capture of Nanning , they continued to be operated in

5544-469: The Navy and the Air Force merged their two nearby bases; Pearl Harbor joined with Hickam Air Force Base to create Joint Base Pearl Harbor–Hickam . In December 2016, Japanese Prime Minister Shinzo Abe made a joint visit to Pearl Harbor with US President Barack Obama . This trip marked the 75th anniversary of the attack and was the first official visit by a sitting Japanese leader. On December 4, 2019,

5643-580: 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

5742-595: The United States for Commerce and Seamen" was appointed to look after American business in the Port of Honolulu . These commercial ties to the American continent were accompanied by the work of the American Board of Commissioners for Foreign Missions . American missionaries and their families became an integral part of the Hawaiian political body. Throughout the 1820s and 1830s, many American warships visited Honolulu. In most cases,

5841-542: The air defense of Hawaii, for American commanders thought the Japanese would attack either Wake Island or the Philippines and had no understanding of the capabilities and proper employment of air power. As it was, had the Pacific Fleet acted on the war warnings, it undoubtedly would have sortied and been at sea on December 7, where the major ships would have been sunk in deep water, making salvage impossible. Shortly after

5940-405: 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

6039-464: The area in 1940. In May 1940, 12th Air Group became the second front-line unit to be equipped with the new D3A1 dive bombers. They first participated in the capture of Yichang and conducted anti-shipping operations on Yangtze river, west of Yichang , in order to cut the Chinese supplies coming from Chongqing . In September, D3A1 from the 12th Air Group started to fly missions against Chongqing , which

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6138-414: 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

6237-520: The commander of a dive bomber. For example, Petty Officer First Class Kiyoto Furuta was serving as a pilot to Lieutenant Takehiko Chihaya during the Attack on Pearl Harbor , and later on to Lieutenant Keiichi Arima during the two carrier battles of the Solomon Islands campaign , both of whom were observers. The D3A1 first saw combat operation in November 1939, one month prior to its official acceptance as

6336-572: The commanding officers carried letters from the U.S. Government giving advice on governmental affairs and of the relations of the island nation with foreign powers. In 1841, the newspaper Polynesian , printed in Honolulu, advocated that the U.S. establish a naval base in Hawaii for the protection of American citizens engaged in the whaling industry. The British Hawaiian Minister of Foreign Affairs Robert Crichton Wyllie , remarked in 1840 that, "... my opinion

6435-668: 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,

6534-466: 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

6633-602: The desire for the United States to have a permanent presence in the Pacific both contributed to the decision. Following the overthrow of the Hawaiian Kingdom, the United States Navy established a base on the island in 1899. On December 7, 1941, the base was attacked by the Imperial Japanese Navy airplanes and midget submarines, causing the American entry into World War II . There was no meaningful plan for

6732-463: The devastating Japanese surprise attack at Pearl Harbor, two American military commanders, Lt. Gen. Walter Short and Adm. Husband Kimmel , were demoted of their full ranks. The two American commanders later sought to restore their reputations and full ranks. Over the years, Pearl Harbor remained a main base for the US Pacific Fleet after World War II along with Naval Base San Diego . In 2010,

6831-404: The dive brakes. Initially, D3A dive bombers were painted in silver. During the summer of 1941, the paint finish changed to light olive grey. The color changed again in early 1942 to dark green. An individual D3A dive bomber was commanded by the senior ranking crew member aboard, which could be the observer rather than the pilot. This was in contrast to US Navy , where the pilot was almost always

6930-480: The estuary already had an outlet for its waters where the present gap is; but Keaunui is typically given the credit for widening and deepening it. During the early nineteenth century, Pearl Harbor was not used for large ships due to its shallow entrance. The United States' interest in the Hawaiian Islands grew as a result of its whaling, shipping and trading activity in the Pacific. As early as 1820, an "Agent of

7029-570: 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

7128-413: 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

7227-580: 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

7326-550: The following year was assigned to cruise among the islands, "a locality of great and increasing interest and importance". This vessel surveyed the Northwestern Hawaiian Islands toward Japan. As a result, the United States claimed Midway Island . The Secretary of the Navy was able to write in his annual report of 1868, that in November 1867, 42 American flags flew over whaleships and merchant vessels in Honolulu to only six of other nations. This increased activity caused

7425-429: The form of the 746 kW (1,000 hp) Kinsei 43 or 798 kW (1,070 hp) Kinsei 44. The directional instability problem was finally cured with the fitting of a long dorsal fin -strake which started midway down the rear fuselage, and the aircraft actually became highly maneuverable. In June 1942, an improved version of D3A1, powered by a 969 kW (1,299 hp) Kinsei 54, was tested and designated as D3A2 or

7524-488: The former two subsequently being asked for two prototypes each. The Aichi design started with low-mounted elliptical wings inspired by the Heinkel He 70 Blitz . It flew slowly enough that the drag from the landing gear was not a serious issue, so the fixed gear was used for simplicity. The aircraft was to be powered by the 529  kW (709  hp ) Nakajima Hikari 1 nine-cylinder radial engine . The first prototype

7623-615: 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

7722-496: The inlet and the right to maintain a repair and coaling station for ships here in 1887. The surprise attack on the harbor by the Imperial Japanese Navy on December 7, 1941, led the United States to declare war on the Empire of Japan , marking the United States' entry into World War II . Pearl Harbor was originally an extensive shallow embayment called Wai Momi (meaning 'Waters of Pearl') or Puʻuloa (meaning 'long hill') by

7821-484: The inner harbor. The United States and the Hawaiian Kingdom signed the Reciprocity Treaty of 1875 as supplemented by Convention on December 6, 1884. This treaty was ratified in 1887. On January 20, 1887, the United States Senate allowed the Navy the exclusive right to maintain a coaling and repair station at Pearl Harbor. (The US took possession on November 9 that year). The Spanish–American War of 1898 and

7920-536: The islands and to the mainland aboard U.S. warships were arranged for members of the Hawaiian royal family and important island government officials. When King Lunalilo died in 1873, negotiations were underway for the cession of Pearl Harbor as a port for the duty-free export of sugar to the U.S. With the election of King Kalākaua in March 1874, a riot prompted landing of sailors from USS Tuscarora and Portsmouth . The British warship, HMS  Tenedos , also landed

8019-402: 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

8118-466: 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

8217-503: The observer position was equipped with a drift meter that was mounted on the floor in the front-right of the observer's seat. The observer also operated a Type 96 Mk2 radio set that was mounted in front of the observer's seat and behind the pilot's seat. On top of the radio set was a Type 3 reflector compass for precise navigation. Armament was two fixed forward-firing 7.7 mm (0.303 in) Type 97 machine guns , and one flexible 7.7 mm (.303 in) Type 92 machine gun at

8316-629: The permanent assignment of at least one warship to Hawaiian waters. It also praised Midway Island as possessing a harbor surpassing Honolulu's. In the following year, Congress approved an appropriation of $ 50,000 on March 1, 1869, to deepen the approaches to this harbor. After 1868, when the Commander of the Pacific Fleet visited the islands to look after American interests, naval officers played an important role in internal affairs. They served as arbitrators in business disputes, negotiators of trade agreements and defenders of law and order. Periodic voyages among

8415-505: 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

8514-451: 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,

8613-409: 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

8712-451: 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

8811-456: 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

8910-406: The rear end of cockpit , which was operated by the observer. Normal bomb load was a single 250 kg bomb (e.g., Type 99 No 25 semi-AP or Type 98 No 25 land bomb) carried under the fuselage, swung out under the propeller on release by a trapeze. Two additional 60 kg bombs (e.g., Type 99 No 6 semi-AP or Type 2 No 6 land bomb) could be carried on wing racks located under each wing outboard of

9009-639: The reserve force was sent with a portion of D3A1 dive bombers armed with land bombs. In the subsequent attack, land bombs unintentionally proved very effective in suppressing the anti-aircraft fire from the ships. As a result, the doctrine was modified in order to intentionally equip the first few D3A1 dive bombers with land bombs. This new method was already implemented for the attack that sank HMS  Hermes just four days later, and continued to be used from then on. During 1942, dive bombing attacks by carrier-based D3A1 and D3A2 bombers significantly contributed to sinking of three US fleet carriers: Lexington at

9108-481: 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

9207-431: 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

9306-483: The war progressed, there were instances when the dive bombers were pressed into duty as fighters in the interceptor role, their maneuverability being enough to allow them to survive in this role. When the Yokosuka D4Y Suisei became available, the D3A2s ended up with land-based units or operating from the smaller carriers, which were too small to handle the fast-landing Suisei . When American forces recaptured

9405-510: 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

9504-585: 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

9603-467: Was completed in December 1937, and flight trials began a month later, after which it was designated as D3A1. Initial tests were disappointing. The aircraft was underpowered and suffered from directional instability in wide turns, and in tighter turns it tended to snap roll . The dive brakes vibrated heavily when extended at their design speed of 200 knots (370 km/h), and the Navy was already asking for

9702-421: Was the Chinese capital at the time. After the invasion of Indochina in autumn 1940, 14th Air Group operated at Hanoi and flew missions against Kunming and Burma Road . The D3A1 commenced carrier qualification trials aboard the aircraft carriers Akagi and Kaga during 1940, while a small number of aircraft made their combat debut from land bases over China . Starting with the attack on Pearl Harbor,

9801-421: Was to arm all D3A1 dive bombers with semi-AP bombs. On 5 April 1942, an IJN carrier force attacked Colombo on Ceylon with half of its complement, while the other half was kept in reserve for strikes against ships. Since a second strike against Colombo was deemed necessary, the dive bombers of the reserve force were rearmed from semi-AP bombs to land bombs. When British heavy cruisers were spotted soon afterwards,

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