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171-421: RDF systems can be used with any radio source, although very long wavelengths (low frequencies) require very large antennas, and are generally used only on ground-based systems. These wavelengths are nevertheless used for marine radio navigation as they can travel very long distances "over the horizon", which is valuable for ships when the line-of-sight may be only a few tens of kilometres. For aerial use, where

342-411: A local wavelength . An example is shown in the figure. In general, the envelope of the wave packet moves at a speed different from the constituent waves. Using Fourier analysis , wave packets can be analyzed into infinite sums (or integrals) of sinusoidal waves of different wavenumbers or wavelengths. Louis de Broglie postulated that all particles with a specific value of momentum p have

513-520: A 14-month circumnavigation of the world. Ordered by President Theodore Roosevelt , it was a mission designed to demonstrate the Navy's capability to extend to the global theater. By 1911, the U.S. had begun building the super-dreadnoughts at a pace to eventually become competitive with Britain. The 1911 also saw the first naval aircraft with the navy which would lead to the informal establishment of United States Naval Flying Corps to protect shore bases. It

684-647: A change in their rating from their previous rating (i.e., MMCM) to CMDCM. The stars for Command Master Chief are silver, while stars for Fleet, and gold stars for Force. Additionally, CMCs wear a badge, worn on their left breast pocket, denoting their title (Command/Fleet/Force). Insignia and badges of the United States Navy are military "badges" issued by the Department of the Navy to naval service members who achieve certain qualifications and accomplishments while serving on both active and reserve duty in

855-455: A circular aperture, the diffraction-limited image spot is known as an Airy disk ; the distance x in the single-slit diffraction formula is replaced by radial distance r and the sine is replaced by 2 J 1 , where J 1 is a first order Bessel function . The resolvable spatial size of objects viewed through a microscope is limited according to the Rayleigh criterion , the radius to

1026-621: A common center point. A movable switch could connect opposite pairs of these wires to form a dipole, and by rotating the switch the operator could hunt for the strongest signal. The US Navy overcame this problem, to a point, by mounting antennas on ships and sailing in circles. Such systems were unwieldily and impractical for many uses. A key improvement in the RDF concept was introduced by Ettore Bellini and Alessandro Tosi in 1909 (U.S. Patent 943,960). Their system used two such antennas, typically triangular loops, arranged at right angles. The signals from

1197-459: A crystal lattice vibration , atomic positions vary. The range of wavelengths or frequencies for wave phenomena is called a spectrum . The name originated with the visible light spectrum but now can be applied to the entire electromagnetic spectrum as well as to a sound spectrum or vibration spectrum . In linear media, any wave pattern can be described in terms of the independent propagation of sinusoidal components. The wavelength λ of

1368-530: A directional antenna is used which is more sensitive in certain directions than in others. Many antenna designs exhibit this property. For example, a Yagi antenna has quite pronounced directionality, so the source of a transmission can be determined by pointing it in the direction where the maximum signal level is obtained. Since the directional characteristics can be very broad, large antennas may be used to improve precision, or null techniques used to improve angular resolution. A simple form of directional antenna

1539-503: A directional antenna pattern, then the amplitude may be included in the comparison. Typically, the correlative interferometer DF system consists of more than five antenna elements. These are scanned one after the other via a specific switching matrix. In a multi-channel DF system n antenna elements are combined with m receiver channels to improve the DF-system performance. Radio direction finding , radio direction finder , or RDF ,

1710-441: A few tens of kilometres. For aircraft, where the horizon at altitude may extend to hundreds of kilometres, higher frequencies can be used, allowing much smaller antennas. An automatic direction finder, often capable of being tuned to commercial AM radio transmitters, is a feature of almost all modern aircraft. For the military, RDF systems are a key component of signals intelligence systems and methodologies. The ability to locate

1881-639: A fleet of mobile DF vehicles around the UK. If a transmitter was identified by the fixed DF stations or voluntary interceptors, the mobile units were sent to the area to home in on the source. The mobile units were HF Adcock systems. By 1941 only a couple of illicit transmitters had been identified in the UK; these were German agents that had been "turned" and were transmitting under MI5 control. Many illicit transmissions had been logged emanating from German agents in occupied and neutral countries in Europe. The traffic became

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2052-466: A formidable force in the years prior to World War II , with battleship production being restarted in 1937, commencing with USS  North Carolina  (BB-55) . Though ultimately unsuccessful, Japan tried to neutralize this strategic threat with the surprise attack on Pearl Harbor on 7 December 1941. Following American entry into the war , the U.S. Navy grew tremendously as the United States

2223-651: A frequent actor in American foreign and military policy. The United States Navy is part of the Department of the Navy , alongside the United States Marine Corps , which is its coequal sister service. The Department of the Navy is headed by the civilian secretary of the Navy . The Department of the Navy is itself a military department of the Department of Defense , which is headed by the secretary of defense . The chief of naval operations (CNO)

2394-437: A known wave angle (reference data set). For this, at least three antenna elements (with omnidirectional reception characteristics) must form a non-collinear basis. The comparison is made for different azimuth and elevation values of the reference data set. The bearing result is obtained from a correlative and stochastic evaluation for which the correlation coefficient is at a maximum. If the direction finding antenna elements have

2565-447: A landfall. In the United States, commercial AM radio stations were required to broadcast their station identifier once per hour for use by pilots and mariners as an aid to navigation. In the 1950s, aviation NDBs were augmented by the VOR system, in which the direction to the beacon can be extracted from the signal itself, hence the distinction with non-directional beacons. Use of marine NDBs

2736-407: A larger electronic warfare suite. Early radio direction finders used mechanically rotated antennas that compared signal strengths, and several electronic versions of the same concept followed. Modern systems use the comparison of phase or doppler techniques which are generally simpler to automate. Early British radar sets were referred to as RDF, which is often stated was a deception. In fact,

2907-468: A linear system the sinusoid is the unique shape that propagates with no shape change – just a phase change and potentially an amplitude change. The wavelength (or alternatively wavenumber or wave vector ) is a characterization of the wave in space, that is functionally related to its frequency, as constrained by the physics of the system. Sinusoids are the simplest traveling wave solutions, and more complex solutions can be built up by superposition . In

3078-642: A major effect on naval planning is the Pivot to East Asia . In response, the Secretary of the Navy Ray Mabus stated in 2015 that 60 percent of the total U.S. fleet will be deployed to the Pacific by 2020. The Navy's most recent 30-year shipbuilding plan, published in 2016, calls for a future fleet of 350 ships to meet the challenges of an increasingly competitive international environment. A provision of

3249-399: A multiple channel receiver system. One form of radio direction finding works by comparing the signal strength of a directional antenna pointing in different directions. At first, this system was used by land and marine-based radio operators, using a simple rotatable loop antenna linked to a degree indicator. This system was later adopted for both ships and aircraft, and was widely used in

3420-635: A national navy was debated in the Second Continental Congress . Supporters argued that a navy would protect shipping, defend the coast, and make it easier to seek support from foreign countries. Detractors countered that challenging the British Royal Navy , then the world's preeminent naval power, was a foolish undertaking. Commander in Chief George Washington resolved the debate when he commissioned

3591-502: A navy able to reform those enemies to mankind or crush them into non-existence. Naval power . . . is the natural defense of the United States. The Navy was rooted in the colonial seafaring tradition, which produced a large community of sailors, captains, and shipbuilders. In the early stages of the American Revolutionary War , Massachusetts had its own Massachusetts Naval Militia . The rationale for establishing

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3762-523: A number of radio DF units located at civil and military airports and certain HM Coastguard stations. These stations can obtain a "fix" of the aircraft and transmit it by radio to the pilot. Radio transmitters for air and sea navigation are known as beacons and are the radio equivalent to a lighthouse . The transmitter sends a Morse Code transmission on a Long wave (150 – 400 kHz) or Medium wave (520 – 1720 kHz) frequency incorporating

3933-464: A number of small antennas fixed to a circular card, with all of the processing performed by software. Early British radar sets were also referred to as RDF, which was a deception tactic. However, the terminology was not inaccurate; the Chain Home systems used separate omnidirectional broadcasters and large RDF receivers to determine the location of the targets. In one type of direction finding,

4104-643: A number of unique capabilities, including Military Sealift Command , Naval Expeditionary Combat Command , and Naval Information Forces . The United States Navy has seven active numbered fleets – Second , Third , Fifth , Sixth , Seventh and Tenth Fleets are each led by a vice admiral , and the Fourth Fleet is led by a rear admiral . These seven fleets are further grouped under Fleet Forces Command (the former Atlantic Fleet), Pacific Fleet, Naval Forces Europe-Africa, and Naval Forces Central Command, whose commander also doubles as Commander Fifth Fleet;

4275-867: A quarter of whom are in ready reserve. Of those on active duty, more than eighty percent are enlisted sailors and around fifteen percent are commissioned officers ; the rest are midshipmen of the United States Naval Academy and midshipmen of the Naval Reserve Officer Training Corps at over 180 universities around the country and officer candidates at the Navy's Officer Candidate School . Enlisted sailors complete basic military training at boot camp and then are sent to complete training for their individual careers . Sailors prove they have mastered skills and deserve responsibilities by completing Personnel Qualification Standards (PQS) tasks and examinations. Among

4446-426: A regular lattice. This produces aliasing because the same vibration can be considered to have a variety of different wavelengths, as shown in the figure. Descriptions using more than one of these wavelengths are redundant; it is conventional to choose the longest wavelength that fits the phenomenon. The range of wavelengths sufficient to provide a description of all possible waves in a crystalline medium corresponds to

4617-432: A result, the change in direction upon entering a different medium changes with the wavelength of the wave. For electromagnetic waves the speed in a medium is governed by its refractive index according to where c is the speed of light in vacuum and n ( λ 0 ) is the refractive index of the medium at wavelength λ 0 , where the latter is measured in vacuum rather than in the medium. The corresponding wavelength in

4788-456: A ring and use electronic switching to rapidly select dipoles to feed into the receiver. The resulting signal is processed and produces an audio tone. The phase of that audio tone, compared to the antenna rotation, depends on the direction of the signal. Doppler RDF systems have widely replaced the huff-duff system for location of fleeting signals. The various procedures for radio direction finding to determine position at sea are no longer part of

4959-465: A senior non-commissioned officer in the other services, and must have a minimum 14 years in service. Sailors in pay grades E-1 through E-3 are considered to be in apprenticeships. They are divided into five definable groups, with colored group rate marks designating the group to which they belong: Seaman, Fireman, Airman, Constructionman, and Hospitalman. E-4 to E-6 are non-commissioned officers (NCOs), and are specifically called Petty officers in

5130-497: A service member may choose to further their career by becoming a Command Master Chief Petty Officer (CMC). A CMC is considered to be the senior-most enlisted service member within a command, and is the special assistant to the Commanding Officer in all matters pertaining to the health, welfare, job satisfaction, morale, use, advancement and training of the command's enlisted personnel. CMCs can be Command level (within

5301-404: A single unit, such as a ship or shore station), Fleet level (squadrons consisting of multiple operational units, headed by a flag officer or commodore), or Force level (consisting of a separate community within the Navy, such as Subsurface, Air, Reserves). CMC insignia are similar to the insignia for Master Chief, except that the rating symbol is replaced by an inverted five-point star, reflecting

Direction finding - Misplaced Pages Continue

5472-411: A sinusoidal waveform traveling at constant speed v {\displaystyle v} is given by where v {\displaystyle v} is called the phase speed (magnitude of the phase velocity ) of the wave and f {\displaystyle f} is the wave's frequency . In a dispersive medium , the phase speed itself depends upon the frequency of the wave, making

5643-597: A small loop's null. For much higher frequencies still, such as millimeter waves and microwaves , parabolic antennas or "dish" antennas can be used. Dish antennas are highly directional, with the parabolic shape directing received signals from a very narrow angle into a small receiving element mounted at the focus of the parabola. More sophisticated techniques such as phased arrays are generally used for highly accurate direction finding systems. The modern systems are called goniometers by analogy to WW II directional circuits used to measure direction by comparing

5814-430: A suitable oscilloscope, and he presented his new system in 1926. In spite of the system being presented publicly, and its measurements widely reported in the UK, its impact on the art of RDF seems to be strangely subdued. Development was limited until the mid-1930s, when the various British forces began widespread development and deployment of these " high-frequency direction finding ", or "huff-duff" systems. To avoid RDF,

5985-404: A traveling wave. For example, the speed of light can be determined from observation of standing waves in a metal box containing an ideal vacuum. Traveling sinusoidal waves are often represented mathematically in terms of their velocity v (in the x direction), frequency f and wavelength λ as: where y is the value of the wave at any position x and time t , and A is the amplitude of

6156-411: A valuable source of intelligence, so the control of RSS was subsequently passed to MI6 who were responsible for secret intelligence originating from outside the UK. The direction finding and interception operation increased in volume and importance until 1945. Wavelength In physics and mathematics , wavelength or spatial period of a wave or periodic function is the distance over which

6327-531: A wavelength λ = h / p , where h is the Planck constant . This hypothesis was at the basis of quantum mechanics . Nowadays, this wavelength is called the de Broglie wavelength . For example, the electrons in a CRT display have a De Broglie wavelength of about 10  m . To prevent the wave function for such a particle being spread over all space, de Broglie proposed using wave packets to represent particles that are localized in space. The spatial spread of

6498-489: A wider electronic warfare suite. Several distinct generations of RDF systems have been used over time, following new developments in electronics. Early systems used mechanically rotated antennas that compared signal strengths from different directions, and several electronic versions of the same concept followed. Modern systems use the comparison of phase or doppler techniques which are generally simpler to automate. Modern pseudo-Doppler direction finder systems consist of

6669-721: Is a distinct, separate service branch with its own uniformed service chief – the Commandant of the Marine Corps, a four-star general. The Marine Corps depends on the Navy for medical support (dentists, doctors , nurses, medical technicians known as corpsmen ) and religious support (chaplains). Thus, Navy officers and enlisted sailors fulfill these roles. When attached to Marine Corps units deployed to an operational environment they generally wear Marine camouflage uniforms, but otherwise, they wear Navy dress uniforms unless they opt to conform to Marine Corps grooming standards. In

6840-424: Is also responsible for the familiar phenomenon in which light is separated into component colours by a prism . Separation occurs when the refractive index inside the prism varies with wavelength, so different wavelengths propagate at different speeds inside the prism, causing them to refract at different angles. The mathematical relationship that describes how the speed of light within a medium varies with wavelength

7011-464: Is an undulatory motion that stays in one place. A sinusoidal standing wave includes stationary points of no motion, called nodes , and the wavelength is twice the distance between nodes. The upper figure shows three standing waves in a box. The walls of the box are considered to require the wave to have nodes at the walls of the box (an example of boundary conditions ), thus determining the allowed wavelengths. For example, for an electromagnetic wave, if

Direction finding - Misplaced Pages Continue

7182-403: Is called diffraction . Two types of diffraction are distinguished, depending upon the separation between the source and the screen: Fraunhofer diffraction or far-field diffraction at large separations and Fresnel diffraction or near-field diffraction at close separations. In the analysis of the single slit, the non-zero width of the slit is taken into account, and each point in the aperture

7353-495: Is described by the Jacobi elliptic function of m th order, usually denoted as cn ( x ; m ) . Large-amplitude ocean waves with certain shapes can propagate unchanged, because of properties of the nonlinear surface-wave medium. If a traveling wave has a fixed shape that repeats in space or in time, it is a periodic wave . Such waves are sometimes regarded as having a wavelength even though they are not sinusoidal. As shown in

7524-729: Is immediately under and reports to the Secretary of the Navy. At the same time, the Chief of Naval Operations is a member of the Joint Chiefs of Staff , which is the second-highest deliberative body of the armed forces after the United States National Security Council , although it plays only an advisory role to the President and does not nominally form part of the chain of command . The Secretary of

7695-457: Is known as radio direction finding or sometimes simply direction finding ( DF ). Using two or more measurements from different locations, the location of an unknown transmitter can be determined; alternately, using two or more measurements of known transmitters, the location of a vehicle can be determined. RDF is widely used as a radio navigation system, especially with boats and aircraft. RDF systems can be used with any radio source, although

7866-413: Is known as a dispersion relation . Wavelength can be a useful concept even if the wave is not periodic in space. For example, in an ocean wave approaching shore, shown in the figure, the incoming wave undulates with a varying local wavelength that depends in part on the depth of the sea floor compared to the wave height. The analysis of the wave can be based upon comparison of the local wavelength with

8037-427: Is large compared to the slit separation d ) then the paths are nearly parallel, and the path difference is simply d sin θ . Accordingly, the condition for constructive interference is: where m is an integer, and for destructive interference is: Thus, if the wavelength of the light is known, the slit separation can be determined from the interference pattern or fringes , and vice versa . For multiple slits,

8208-517: Is now only one position as the loop rotates 360° at which there is zero current. This acts as a phase reference point, allowing the correct null point to be identified, removing the 180° ambiguity. A dipole antenna exhibits similar properties, as a small loop, although its null direction is not as "sharp". The Yagi-Uda antenna is familiar as the common VHF or UHF television aerial. A Yagi antenna uses multiple dipole elements, which include "reflector" and "director" dipole elements. The "reflector"

8379-488: Is related to position x via a squared sinc function : where L is the slit width, R is the distance of the pattern (on the screen) from the slit, and λ is the wavelength of light used. The function S has zeros where u is a non-zero integer, where are at x values at a separation proportion to wavelength. Diffraction is the fundamental limitation on the resolving power of optical instruments, such as telescopes (including radiotelescopes ) and microscopes . For

8550-458: Is taken as the source of one contribution to the beam of light ( Huygens' wavelets ). On the screen, the light arriving from each position within the slit has a different path length, albeit possibly a very small difference. Consequently, interference occurs. In the Fraunhofer diffraction pattern sufficiently far from a single slit, within a small-angle approximation , the intensity spread S

8721-409: Is the loop aerial . This consists of an open loop of wire on an insulating frame, or a metal ring that forms the antenna's loop element itself; often the diameter of the loop is a tenth of a wavelength or smaller at the target frequency. Such an antenna will be least sensitive to signals that are perpendicular to its face and most responsive to those arriving edge-on. This is caused by the phase of

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8892-452: Is the longest dipole element and blocks nearly all the signal coming from behind it, hence a Yagi has no front vs. back directional ambiguity: The maximum signal only occurs when the narrowest end of the Yagi is aimed in the direction from which the radio waves are arriving. With a sufficient number of shorter "director" elements, a Yagi's maximum direction can be made to approach the sharpness of

9063-420: Is the most senior Navy officer serving in the Department of the Navy. To recruit, train, equip, and organize to deliver combat ready Naval forces to win conflicts and wars while maintaining security and deterrence through sustained forward presence. The U.S. Navy is a seaborne branch of the military of the United States . The Navy's three primary areas of responsibility: U.S. Navy training manuals state that

9234-417: Is used in the interferometer . A simple example is an experiment due to Young where light is passed through two slits . As shown in the figure, light is passed through two slits and shines on a screen. The path of the light to a position on the screen is different for the two slits, and depends upon the angle θ the path makes with the screen. If we suppose the screen is far enough from the slits (that is, s

9405-596: The 1966 Palomares B-52 crash incident and the subsequent search for missing hydrogen bombs, and Task Force 71 of the Seventh Fleet's operation in search for Korean Air Lines Flight 007 , shot down by the Soviets on 1 September 1983. The U.S. Navy continues to be a major support to U.S. interests in the 21st century. Since the end of the Cold War, it has shifted its focus from preparations for large-scale war with

9576-662: The American Civil War , in which the Union had a distinct advantage over the Confederacy on the seas. A Union blockade on all major ports shut down exports and the coastal trade, but blockade runners provided a thin lifeline. The Brown-water navy components of the U.S. navy control of the river systems made internal travel difficult for Confederates and easy for the Union. The war saw ironclad warships in combat for

9747-655: The Battle of Okinawa . By 1943, the navy's size was larger than the combined fleets of all the other combatant nations in World War II. By war's end in 1945, the U.S. Navy had added hundreds of new ships, including 18 aircraft carriers and 8 battleships, and had over 70% of the world's total numbers and total tonnage of naval vessels of 1,000 tons or greater. At its peak, the U.S. Navy was operating 6,768 ships on V-J Day in August 1945. Doctrine had significantly shifted by

9918-900: The Bureau of Naval Personnel , the Office of Naval Research , the Office of Naval Intelligence , the United States Naval Academy , the Naval Safety Command , the Naval Aviation Warfighting Development Center , and the United States Naval Observatory . Official Navy websites list the Office of the Chief of Naval Operations and the Chief of Naval Operations as part of the shore establishment, but these two entities effectively sit superior to

10089-426: The Chain Home systems used large RDF receivers to determine directions. Later radar systems generally used a single antenna for broadcast and reception, and determined direction from the direction the antenna was facing. The earliest experiments in RDF were carried out in 1888 when Heinrich Hertz discovered the directionality of an open loop of wire used as an antenna. When the antenna was aligned so it pointed at

10260-523: The Greek letter lambda ( λ ). The term "wavelength" is also sometimes applied to modulated waves, and to the sinusoidal envelopes of modulated waves or waves formed by interference of several sinusoids. Assuming a sinusoidal wave moving at a fixed wave speed, wavelength is inversely proportional to the frequency of the wave: waves with higher frequencies have shorter wavelengths, and lower frequencies have longer wavelengths. Wavelength depends on

10431-613: The Ready Reserve , the U.S. Navy is the third largest of the United States military service branches in terms of personnel. It has 299 deployable combat vessels and about 4,012 operational aircraft as of July 18, 2023. The United States Navy traces its origins to the Continental Navy , which was established during the American Revolutionary War and was effectively disbanded as a separate entity shortly thereafter. After suffering significant loss of goods and personnel at

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10602-526: The aviation world. Starting in the 1950s, these beacons were generally replaced by the VOR system, in which the bearing to the navigational aid is measured from the signal itself; therefore no specialized antenna with moving parts is required. Due to relatively low purchase, maintenance and calibration cost, NDBs are still used to mark locations of smaller aerodromes and important helicopter landing sites. Similar beacons located in coastal areas are also used for maritime radio navigation, as almost every ship

10773-422: The cosine phase instead of the sine phase when describing a wave is based on the fact that the cosine is the real part of the complex exponential in the wave The speed of a wave depends upon the medium in which it propagates. In particular, the speed of light in a medium is less than in vacuum , which means that the same frequency will correspond to a shorter wavelength in the medium than in vacuum, as shown in

10944-451: The ionosphere . The RDF station might now receive the same signal from two or more locations, especially during the day, which caused serious problems trying to determine the location. This led to the 1919 introduction of the Adcock antenna (UK Patent 130,490), which consisted of four separate monopole antennas instead of two loops, eliminating the horizontal components and thus filtering out

11115-439: The limited duty officer (LDO) in the Navy. Warrant officers perform duties that are directly related to their previous enlisted service and specialized training. This allows the Navy to capitalize on the experience of warrant officers without having to frequently transition them to other duty assignments for advancement. Most Navy warrant officers are accessed from the chief petty officer pay grades, E-7 through E-9, analogous to

11286-532: The relationship between wavelength and frequency nonlinear. In the case of electromagnetic radiation —such as light—in free space , the phase speed is the speed of light , about 3 × 10  m/s . Thus the wavelength of a 100 MHz electromagnetic (radio) wave is about: 3 × 10  m/s divided by 10  Hz = 3 m. The wavelength of visible light ranges from deep red , roughly 700  nm , to violet , roughly 400 nm (for other examples, see electromagnetic spectrum ). For sound waves in air,

11457-410: The sky waves being reflected down from the ionosphere. Adcock antennas were widely used with Bellini–Tosi detectors from the 1920s on. The US Army Air Corps in 1931 tested a primitive radio compass that used commercial stations as the beacon. A major improvement in the RDF technique was introduced by Robert Watson-Watt as part of his experiments to locate lightning strikes as a method to indicate

11628-443: The speed of sound is 343 m/s (at room temperature and atmospheric pressure ). The wavelengths of sound frequencies audible to the human ear (20  Hz –20 kHz) are thus between approximately 17  m and 17  mm , respectively. Somewhat higher frequencies are used by bats so they can resolve targets smaller than 17 mm. Wavelengths in audible sound are much longer than those in visible light. A standing wave

11799-406: The 1930s and 1940s. On pre- World War II aircraft, RDF antennas are easy to identify as the circular loops mounted above or below the fuselage. Later loop antenna designs were enclosed in an aerodynamic, teardrop-shaped fairing. In ships and small boats, RDF receivers first employed large metal loop antennas, similar to aircraft, but usually mounted atop a portable battery-powered receiver. In use,

11970-521: The 1960s, many of these radios were actually made by Japanese electronics manufacturers, such as Panasonic , Fuji Onkyo , and Koden Electronics Co., Ltd. In aircraft equipment, Bendix and Sperry-Rand were two of the larger manufacturers of RDF radios and navigation instruments. Single-channel DF uses a multi-antenna array with a single channel radio receiver. This approach to DF offers some advantages and drawbacks. Since it only uses one receiver, mobility and lower power consumption are benefits. Without

12141-418: The 2018 National Defense Authorization Act called for expanding the naval fleet to 355 ships "as soon as practicable", but did not establish additional funding nor a timeline. The U.S. Navy falls under the administration of the Department of the Navy , under civilian leadership of the Secretary of the Navy (SECNAV). The most senior naval officer is the Chief of Naval Operations (CNO), a four-star admiral who

12312-563: The Barbary pirates, blockaded the Barbary ports and executed attacks against the Barbary' fleets. The U.S. Navy saw substantial action in the War of 1812 , where it was victorious in eleven single-ship duels with the Royal Navy. It proved victorious in the Battle of Lake Erie and prevented the region from becoming a threat to American operations in the area. The result was a major victory for

12483-534: The Chief of Naval Operations, Admiral Elmo Zumwalt , authorized the Navy to celebrate its birthday on 13 October to honor the establishment of the Continental Navy in 1775. The United States was without a navy for nearly a decade, a state of affairs that exposed U.S. maritime merchant ships to a series of attacks by the Barbary pirates . The sole armed maritime presence between 1790 and the launching of

12654-563: The Coast Guard may be called upon to operate as a service within the Navy. At other times, Coast Guard Port Security Units are sent overseas to guard the security of ports and other assets. The Coast Guard also jointly staffs the Navy's naval coastal warfare groups and squadrons (the latter of which were known as harbor defense commands until late-2004), which oversee defense efforts in foreign littoral combat and inshore areas. The United States Navy has over 400,000 personnel, approximately

12825-577: The Germans had developed a method of broadcasting short messages under 30 seconds, less than the 60 seconds that a trained Bellini-Tosi operator would need to determine the direction. However, this was useless against huff-duff systems, which located the signal with reasonable accuracy in seconds. The Germans did not become aware of this problem until the middle of the war, and did not take any serious steps to address it until 1944. By that time huff-duff had helped in about one-quarter of all successful attacks on

12996-795: The Mediterranean, where it participated in the Second Barbary War that ended piracy in the region, South America, Africa, and the Pacific. From 1819 to the outbreak of the Civil War, the Africa Squadron operated to suppress the slave trade , seizing 36 slave ships, although its contribution was smaller than that of the much larger British Royal Navy. After 1840 several secretaries of the navy were southerners who advocated for strengthening southern naval defenses, expanding

13167-734: The Navy and Chief of Naval Operations are responsible for organizing, recruiting, training, and equipping the Navy so that it is ready for operation under the commanders of the unified combatant commands . There are nine components in the operating forces of the U.S. Navy: the United States Fleet Forces Command (formerly United States Atlantic Fleet), United States Pacific Fleet , United States Naval Forces Central Command , United States Naval Forces Europe , Naval Network Warfare Command , Navy Reserve , United States Naval Special Warfare Command , and Operational Test and Evaluation Force . Fleet Forces Command controls

13338-461: The Navy reactivated the Fourth Fleet to control operations in the area controlled by Southern Command, which consists of US assets in and around Central and South America. Other number fleets were activated during World War II and later deactivated, renumbered, or merged. Shore establishments exist to support the mission of the fleet through the use of facilities on land. Among the commands of

13509-424: The Navy. Petty Officers perform not only the duties of their specific career field but also serve as leaders to junior enlisted personnel. E-7 to E-9 are still considered Petty Officers, but are considered a separate community within the Navy. They have separate berthing and dining facilities (where feasible), wear separate uniforms, and perform separate duties. After attaining the rate of Master Chief Petty Officer,

13680-455: The N–S (North-South) and E–W (East-West) signals that will then be passed to the receiver. In the receiver, the bearing angle can then be computed by taking the arctangent of the ratio of the N–S to E–W signal. The basic principle of the correlative interferometer consists in comparing the measured phase differences with the phase differences obtained for a DF antenna system of known configuration at

13851-433: The RDF operator would first tune the receiver to the correct frequency, then manually turn the loop, either listening or watching an S meter to determine the direction of the null (the direction at which a given signal is weakest) of a long wave (LW) or medium wave (AM) broadcast beacon or station (listening for the null is easier than listening for a peak signal, and normally produces a more accurate result). This null

14022-723: The Soviet Union to special operations and strike missions in regional conflicts. The navy participated in Operation Enduring Freedom , Operation Iraqi Freedom , and is a major participant in the ongoing War on Terror , largely in this capacity. Development continues on new ships and weapons, including the Gerald R. Ford -class aircraft carrier and the Littoral combat ship . Because of its size, weapons technology, and ability to project force far from U.S. shores,

14193-659: The U-boat fleet. Several developments in electronics during and after the Second World War led to greatly improved methods of comparing the phase of signals. In addition, the phase-locked loop (PLL) allowed for easy tuning in of signals, which would not drift. Improved vacuum tubes and the introduction of the transistor allowed much higher frequencies to be used economically, which led to widespread use of VHF and UHF signals. All of these changes led to new methods of RDF, and its much more widespread use. In particular,

14364-755: The U.S. Army at the Niagara Frontier of the war, and the defeat of the Native American allies of the British at the Battle of the Thames . Despite this, the U.S. Navy could not prevent the British from blockading its ports and landing troops. But after the War of 1812 ended in 1815, the U.S. Navy primarily focused its attention on protecting American shipping assets, sending squadrons to the Caribbean,

14535-469: The U.S. Navy and its decisive victory over the outdated Spanish Navy in 1898 brought a new respect for American technical quality. Rapid building of at first pre-dreadnoughts, then dreadnoughts brought the U.S. in line with the navies of countries such as Britain and Germany. In 1907, most of the Navy's battleships, with several support vessels, dubbed the Great White Fleet , were showcased in

14706-614: The U.S. Navy's first warships in 1797 was the U.S. Revenue-Marine , the primary predecessor of the U.S. Coast Guard . Although the United States Revenue Cutter Service conducted operations against the pirates, the pirates' depredations far outstripped its abilities and Congress passed the Naval Act of 1794 that established a permanent standing navy on 27 March 1794. The Naval Act ordered the construction and manning of six frigates and, by October 1797,

14877-401: The U.S. economy and quality of life. This new strategy charts a course for the Navy, Coast Guard, and Marine Corps to work collectively with each other and international partners to prevent these crises from occurring or reacting quickly should one occur to prevent negative impacts on the U.S. In 2010, Admiral Gary Roughead, Chief of Naval Operations, noted that demands on the Navy have grown as

15048-412: The UK was installing sufficient DF stations to cover the entire area to receive skywave signals reflected back from the ionised layers in the upper atmosphere. Even with the expanded network, some areas were not adequately covered and for this reason up to 1700 voluntary interceptors (radio amateurs) were recruited to detect illicit transmissions by ground wave . In addition to the fixed stations, RSS ran

15219-454: The UK, and Search and Rescue helicopters have direction finding receivers for marine VHF signals and the 121.5 MHz homing signals incorporated in EPIRB and PLB beacons, although modern GPS-EPIRBS and AIS beacons are slowly making these redundant. A radio direction finder ( RDF ) is a device for finding the direction, or bearing , to a radio source. The act of measuring the direction

15390-438: The United States . It is the world's most powerful navy and the largest by tonnage, at 4.5 million tons in 2021 and in 2009 an estimated battle fleet tonnage that exceeded the next 13 navies combined. It has the world's largest aircraft carrier fleet, with 11 in service , one undergoing trials, two new carriers under construction, and six other carriers planned as of 2024. With 336,978 personnel on active duty and 101,583 in

15561-525: The United States Navy grew under an ambitious ship building program associated with the Naval Act of 1916 . Naval construction, especially of battleships, was limited by the Washington Naval Conference of 1921–22, the first arms control conference in history. The aircraft carriers USS  Saratoga  (CV-3) and USS  Lexington  (CV-2) were built on the hulls of partially built battle cruisers that had been canceled by

15732-450: The ability to compare the phase of signals led to phase-comparison RDF, which is perhaps the most widely used technique today. In this system the loop antenna is replaced with a single square-shaped ferrite core , with loops wound around two perpendicular sides. Signals from the loops are sent into a phase comparison circuit, whose output phase directly indicates the direction of the signal. By sending this to any manner of display, and locking

15903-400: The ability to look at each antenna simultaneously (which would be the case if one were to use multiple receivers, also known as N-channel DF) more complex operations need to occur at the antenna in order to present the signal to the receiver. The two main categories that a single channel DF algorithm falls into are amplitude comparison and phase comparison . Some algorithms can be hybrids of

16074-429: The aircraft's radio set. Bellini–Tosi direction finders were widespread from the 1920s into the 1950s. Early RDF systems were useful largely for long wave signals. These signals are able to travel very long distances, which made them useful for long-range navigation. However, when the same technique was being applied to higher frequencies, unexpected difficulties arose due to the reflection of high frequency signals from

16245-471: The antennas were sent into coils wrapped around a wooden frame about the size of a pop can , where the signals were re-created in the area between the coils. A separate loop antenna located in this area could then be used to hunt for the direction, without moving the main antennas. This made RDF so much more practical that it was soon being used for navigation on a wide scale, often as the first form of aerial navigation available, with ground stations homing in on

16416-399: The box has ideal conductive walls, the condition for nodes at the walls results because the conductive walls cannot support a tangential electric field, forcing the wave to have zero amplitude at the wall. The stationary wave can be viewed as the sum of two traveling sinusoidal waves of oppositely directed velocities. Consequently, wavelength, period, and wave velocity are related just as for

16587-679: The burden of retaliating against the Japanese on the small number of aircraft carriers. During World War II some 4,000,000 Americans served in the United States Navy. The potential for armed conflict with the Soviet Union during the Cold War pushed the U.S. Navy to continue its technological advancement by developing new weapons systems, ships, and aircraft. U.S. naval strategy changed to that of forward deployment in support of U.S. allies with an emphasis on carrier battle groups. The navy

16758-490: The capture of California with large-scale land operations coordinated with the local militia organized in the California Battalion . The Navy conducted the U.S. military's first large-scale amphibious joint operation by successfully landing 12,000 army troops with their equipment in one day at Veracruz , Mexico. When larger guns were needed to bombard Veracruz, Navy volunteers landed large guns and manned them in

16929-560: The central bright portion (radius to first null of the Airy disk ) of the image diffracted by a circular aperture, a measure most commonly used for telescopes and cameras, is: US Navy 13 October 1775 (249 years, 1 month) (as the Continental Navy ) The United States Navy ( USN ) is the maritime service branch of the United States Armed Forces and one of the eight uniformed services of

17100-449: The correct bearing and allowed the navigator to avoid plotting a bearing 180 degrees opposite the actual heading. The U.S. Navy RDF model SE 995 which used a sense antenna was in use during World War I. After World War II, there were many small and large firms making direction finding equipment for mariners, including Apelco , Aqua Guide, Bendix , Gladding (and its marine division, Pearce-Simpson), Ray Jefferson, Raytheon , and Sperry . By

17271-411: The current U.S. Navy remains an asset for the United States. Moreover, it is the principal means through which the U.S. maintains international global order, namely by safeguarding global trade and protecting allied nations. In 2007, the U.S. Navy joined with the U.S. Marine Corps and U.S. Coast Guard to adopt a new maritime strategy called A Cooperative Strategy for 21st Century Seapower that raises

17442-529: The differences in two or more matched reference antennas' received signals, used in old signals intelligence (SIGINT). A modern helicopter -mounted direction finding system was designed by ESL Incorporated for the U.S. Government as early as 1972. Time difference of arrival techniques compare the arrival time of a radio wave at two or more different antennas and deduce the direction of arrival from this timing information. This method can use mechanically simple non-moving omnidirectional antenna elements fed into

17613-569: The direction and wavenumber of a plane wave in 3-space , parameterized by position vector r . In that case, the wavenumber k , the magnitude of k , is still in the same relationship with wavelength as shown above, with v being interpreted as scalar speed in the direction of the wave vector. The first form, using reciprocal wavelength in the phase, does not generalize as easily to a wave in an arbitrary direction. Generalizations to sinusoids of other phases, and to complex exponentials, are also common; see plane wave . The typical convention of using

17784-509: The direction of thunderstorms for sailors and airmen. He had long worked with conventional RDF systems, but these were difficult to use with the fleeting signals from the lightning. He had early on suggested the use of an oscilloscope to display these near instantly, but was unable to find one while working at the Met Office . When the office was moved, his new location at a radio research station provided him with both an Adcock antenna and

17955-464: The end of the war. The U.S. Navy had followed in the footsteps of the navies of Great Britain and Germany which favored concentrated groups of battleships as their main offensive naval weapons. The development of the aircraft carrier and its devastating use by the Japanese against the U.S. at Pearl Harbor, however, shifted U.S. thinking. The Pearl Harbor attack destroyed or took out of action a significant number of U.S. Navy battleships. This placed much of

18126-526: The face of the expiration of budget relief offered by the Bipartisan Budget Act of 2013 and CNO Jonathan Greenert said that a ten ship carrier fleet would not be able to sustainably support military requirements. The British First Sea Lord George Zambellas said that the USN had switched from "outcome-led to resource-led" planning. One significant change in U.S. policymaking that is having

18297-407: The figure at right. This change in speed upon entering a medium causes refraction , or a change in direction of waves that encounter the interface between media at an angle. For electromagnetic waves , this change in the angle of propagation is governed by Snell's law . The wave velocity in one medium not only may differ from that in another, but the velocity typically varies with wavelength. As

18468-400: The figure, wavelength is measured between consecutive corresponding points on the waveform. Localized wave packets , "bursts" of wave action where each wave packet travels as a unit, find application in many fields of physics. A wave packet has an envelope that describes the overall amplitude of the wave; within the envelope, the distance between adjacent peaks or troughs is sometimes called

18639-471: The first null of the Airy disk, to a size proportional to the wavelength of the light used, and depending on the numerical aperture : where the numerical aperture is defined as N A = n sin ⁡ θ {\displaystyle \mathrm {NA} =n\sin \theta \;} for θ being the half-angle of the cone of rays accepted by the microscope objective . The angular size of

18810-654: The first three commands being led by four-star admirals. The United States First Fleet existed after World War II from 1947, but it was redesignated the Third Fleet in early 1973. The Second Fleet was deactivated in September 2011 but reestablished in August 2018 amid heightened tensions with Russia. It is headquartered in Norfolk, Virginia, with responsibility over the East Coast and North Atlantic. In early 2008,

18981-566: The first three were brought into service: USS  United States , USS  Constellation , and USS  Constitution . Due to his strong posture on having a strong standing Navy during this period, John Adams is "often called the father of the American Navy". In 1798–99 the Navy was involved in an undeclared Quasi-War with France. From 1801 to 1805, in the First Barbary War , the U.S. Navy defended U.S. ships from

19152-424: The first time at the Battle of Hampton Roads in 1862, which pitted USS  Monitor against CSS  Virginia . For two decades after the war, however, the U.S. Navy's fleet was neglected and became technologically obsolete . A modernization program beginning in the 1880s when the first steel-hulled warships stimulated the American steel industry, and "the new steel navy" was born. This rapid expansion of

19323-491: The first uniform regulations for officers were issued in 1802 on the formation of the Navy Department. The predominant colors of U.S. Navy uniforms are navy blue and white. U.S. Navy uniforms were based on Royal Navy uniforms of the time and have tended to follow that template. Navy officers serve either as a line officer or as a staff corps officer . Line officers wear an embroidered gold star above their rank of

19494-456: The fleet has shrunk and that in the face of declining budgets in the future, the U.S. Navy must rely even more on international partnerships. In its 2013 budget request, the navy focused on retaining all eleven big deck carriers, at the expense of cutting numbers of smaller ships and delaying the SSBN replacement. By the next year the USN found itself unable to maintain eleven aircraft carriers in

19665-705: The fleet, and making naval technological improvements. During the Mexican–American War the U.S. Navy blockaded Mexican ports, capturing or burning the Mexican fleet in the Gulf of California and capturing all major cities in Baja California peninsula. In 1846–1848 the Navy successfully used the Pacific Squadron under Commodore Robert F. Stockton and its marines and blue-jackets to facilitate

19836-415: The ground, and thereby provided excellent great circle route ground wave propagation that pointed directly to the transmitter. Methods of performing RDF on longwave signals was a major area of research during the 1900s and 1910s. Antennas are generally sensitive to signals only when they have a length that is a significant portion of the wavelength, or larger. Most antennas are at least 1 ⁄ 4 of

20007-588: The hands of the Barbary pirates from Algiers , the United States Congress passed the Naval Act of 1794 for the construction of six heavy frigates , the first ships of the Navy. The United States Navy played a major role in the American Civil War by blockading the Confederacy and seizing control of its rivers. It played the central role in the World War II defeat of Imperial Japan . The United States Navy emerged from World War II as

20178-431: The horizon may extend to hundreds of kilometres, higher frequencies can be used, allowing the use of much smaller antennas. An automatic direction finder , which could be tuned to radio beacons called non-directional beacons or commercial AM radio broadcasters, was in the 20th century a feature of most aircraft, but is being phased out. For the military, RDF is a key tool of signals intelligence . The ability to locate

20349-545: The incoming signal. The popular Watson-Watt method uses an array of two orthogonal coils (magnetic dipoles) in the horizontal plane, often completed with an omnidirectional vertically polarized electric dipole to resolve 180° ambiguities. The Adcock antenna array uses a pair of monopole or dipole antennas that takes the vector difference of the received signal at each antenna so that there is only one output from each pair of antennas. Two of these pairs are co-located but perpendicularly oriented to produce what can be referred to as

20520-413: The intersecting bearings, the navigator could locate the relative position of his ship or aircraft. Later, RDF sets were equipped with rotatable ferrite loopstick antennas, which made the sets more portable and less bulky. Some were later partially automated by means of a motorized antenna (ADF). A key breakthrough was the introduction of a secondary vertical whip or 'sense' antenna that substantiated

20691-405: The light is not altered, just where it shows up. The notion of path difference and constructive or destructive interference used above for the double-slit experiment applies as well to the display of a single slit of light intercepted on a screen. The main result of this interference is to spread out the light from the narrow slit into a broader image on the screen. This distribution of wave energy

20862-411: The local water depth. Waves that are sinusoidal in time but propagate through a medium whose properties vary with position (an inhomogeneous medium) may propagate at a velocity that varies with position, and as a result may not be sinusoidal in space. The figure at right shows an example. As the wave slows down, the wavelength gets shorter and the amplitude increases; after a place of maximum response,

21033-520: The location of the station and its transmitter, which can reduce the accuracy of the 'fix' when approaching the broadcast city. A second factor is that some AM radio stations are omnidirectional during the day, and switch to a reduced power, directional signal at night. RDF was once the primary form of aircraft and marine navigation. Strings of beacons formed "airways" from airport to airport, while marine NDBs and commercial AM broadcast stations provided navigational assistance to small watercraft approaching

21204-538: The maritime safety system GMDSS , which has been in force since 1999. The striking cross frame antenna with attached auxiliary antenna can only be found on the signal masts of some older ships because they do not interfere there and dismantling would be too expensive. Modern positioning methods such as GPS, DGPS, radar and the now-outdated Loran C have radio direction finding methods that are imprecise for today's needs. Radio direction finding networks also no longer exist. However rescue vessels, such as RNLI lifeboats in

21375-416: The medium (for example, vacuum, air, or water) that a wave travels through. Examples of waves are sound waves , light , water waves and periodic electrical signals in a conductor . A sound wave is a variation in air pressure , while in light and other electromagnetic radiation the strength of the electric and the magnetic field vary. Water waves are variations in the height of a body of water. In

21546-407: The medium is When wavelengths of electromagnetic radiation are quoted, the wavelength in vacuum usually is intended unless the wavelength is specifically identified as the wavelength in some other medium. In acoustics, where a medium is essential for the waves to exist, the wavelength value is given for a specified medium. The variation in speed of light with wavelength is known as dispersion , and

21717-468: The mission of the U.S. Armed Forces is "to be prepared to conduct prompt and sustained combat operations in support of the national interest." The Navy's five enduring functions are: sea control , power projection , deterrence , maritime security , and sealift . It follows then as certain as that night succeeds the day, that without a decisive naval force we can do nothing definitive, and with it, everything honorable and glorious. Would to Heaven we had

21888-529: The most common ground since aircrews are guided in their use of aircraft by standard procedures outlined in a series of publications known as NATOPS manuals. The United States Coast Guard , in its peacetime role with the Department of Homeland Security , fulfills its law enforcement and rescue role in the maritime environment. It provides Law Enforcement Detachments (LEDETs) to Navy vessels, where they perform arrests and other law enforcement duties during naval boarding and interdiction missions. In times of war,

22059-476: The most important is the "warfare qualification", which denotes a journeyman level of capability in Surface Warfare, Aviation Warfare, Information Dominance Warfare, Naval Aircrew, Special Warfare, Seabee Warfare, Submarine Warfare or Expeditionary Warfare. Many qualifications are denoted on a sailor's uniform with U.S. Navy badges and insignia . The uniforms of the U.S. Navy have evolved gradually since

22230-597: The most powerful navy in the world. The modern United States Navy maintains a sizable global presence, deploying in strength in such areas as the Western Pacific , the Mediterranean , and the Indian Ocean. It is a blue-water navy with the ability to project force onto the littoral regions of the world, engage in forward deployments during peacetime and rapidly respond to regional crises, making it

22401-495: The naval service dress uniform while staff corps officers and commissioned warrant officers wear unique designator insignias that denotes their occupational specialty. Warrant and chief warrant officer ranks are held by technical specialists who direct specific activities essential to the proper operation of the ship, which also require commissioned officer authority. Navy warrant officers serve in 30 specialties covering five categories. Warrant officers should not be confused with

22572-719: The notion of prevention of war to the same philosophical level as the conduct of war. The strategy was presented by the Chief of Naval Operations , the Commandant of the Marine Corps , and Commandant of the Coast Guard at the International Sea Power Symposium in Newport, Rhode Island on 17 October 2007. The strategy recognized the economic links of the global system and how any disruption due to regional crises (man-made or natural) can adversely impact

22743-410: The number two official in the Navy Department during World War I, appreciated the Navy and gave it strong support. In return, senior leaders were eager for innovation and experimented with new technologies, such as magnetic torpedoes, and developed a strategy called War Plan Orange for victory in the Pacific in a hypothetical war with Japan that would eventually become reality. The U.S. Navy grew into

22914-539: The ocean-going schooner USS Hannah to interdict British merchantmen and reported the captures to the Congress. On 13 October 1775, the Continental Congress authorized the purchase of two vessels to be armed for a cruise against British merchantmen; this resolution created the Continental Navy and is considered the first establishment of the U.S. Navy. The Continental Navy achieved mixed results; it

23085-427: The operational environment, as an expeditionary force specializing in amphibious operations, Marines often embark on Navy ships to conduct operations from beyond territorial waters. Marine units deploying as part of a Marine Air-Ground Task Force (MAGTF) operate under the command of the existing Marine chain of command. Although Marine units routinely operate from amphibious assault ships, the relationship has evolved over

23256-451: The other organizations, playing a coordinating role. In 1834, the United States Marine Corps came under the Department of the Navy. Historically, the Navy has had a unique relationship with the USMC, partly because they both specialize in seaborne operations. Together the Navy and Marine Corps form the Department of the Navy and report to the Secretary of the Navy. However, the Marine Corps

23427-413: The pattern is where q is the number of slits, and g is the grating constant. The first factor, I 1 , is the single-slit result, which modulates the more rapidly varying second factor that depends upon the number of slits and their spacing. In the figure I 1 has been set to unity, a very rough approximation. The effect of interference is to redistribute the light, so the energy contained in

23598-495: The position of an enemy transmitter has been invaluable since World War I , and it played a key role in World War II 's Battle of the Atlantic . It is estimated that the UK's advanced " huff-duff " systems were directly or indirectly responsible for 24% of all U-boats sunk during the war. Modern systems often use phased array antennas to allow rapid beam forming for highly accurate results. These are generally integrated into

23769-412: The position of an enemy transmitter has been invaluable since World War I, and played a key role in World War II's Battle of the Atlantic . It is estimated that the UK's advanced " huff-duff " systems were directly or indirectly responsible for 24% of all U-boats sunk during the war. Modern systems often used phased array antennas to allow rapid beamforming for highly accurate results, and are part of

23940-402: The radio waves could be arriving. This is called a null in the signal, and it is used instead of the strongest signal direction, because small angular deflections of the loop aerial away from its null positions produce much more abrupt changes in received current than similar directional changes around the loop's strongest signal orientation. Since the null direction gives a clearer indication of

24111-473: The received signal: The difference in electrical phase along the rim of the loop at any instant causes a difference in the voltages induced on either side of the loop. Turning the plane of the loop to "face" the signal so that the arriving phases are identical around the entire rim will not induce any current flow in the loop. So simply turning the antenna to produce a minimum in the desired signal will establish two possible directions (front and back) from which

24282-663: The senior command meant that naval forces were not contributed until late 1917. Battleship Division Nine was dispatched to Britain and served as the Sixth Battle Squadron of the British Grand Fleet. Its presence allowed the British to decommission some older ships and reuse the crews on smaller vessels. Destroyers and U.S. Naval Air Force units like the Northern Bombing Group contributed to the anti-submarine operations. The strength of

24453-1052: The shore establishment, as of April 2011 , are the Naval Education and Training Command , the Navy Installations Command , the Naval Meteorology and Oceanography Command , the Naval Information Warfare Systems Command , the Naval Facilities Engineering Command , the Naval Supply Systems Command , the Naval Air Systems Command , the Naval Sea Systems Command , the Bureau of Medicine and Surgery ,

24624-537: The short wavelength is associated with a high loss and the wave dies out. The analysis of differential equations of such systems is often done approximately, using the WKB method (also known as the Liouville–Green method ). The method integrates phase through space using a local wavenumber , which can be interpreted as indicating a "local wavelength" of the solution as a function of time and space. This method treats

24795-426: The signal direction – the null is "sharper" than the max – with loop aerial the null direction is used to locate a signal source. A "sense antenna" is used to resolve the two direction possibilities; the sense aerial is a non-directional antenna configured to have the same sensitivity as the loop aerial. By adding the steady signal from the sense aerial to the alternating signal from the loop signal as it rotates, there

24966-453: The signal it produced maximum gain, and produced zero signal when face on. This meant there was always an ambiguity in the location of the signal: it would produce the same output if the signal was in front or back of the antenna. Later experimenters also used dipole antennas , which worked in the opposite sense, reaching maximum gain at right angles and zero when aligned. RDF systems using mechanically swung loop or dipole antennas were common by

25137-401: The signal using PLL, the direction to the broadcaster can be continuously displayed. Operation consists solely of tuning in the station, and is so automatic that these systems are normally referred to as automatic direction finder . Other systems have been developed where more accuracy is required. Pseudo-doppler radio direction finder systems use a series of small dipole antennas arranged in

25308-402: The size of the receiver antennas are a function of the wavelength of the signal; very long wavelengths (low frequencies) require very large antennas, and are generally used only on ground-based systems. These wavelengths are nevertheless very useful for marine navigation as they can travel very long distances and "over the horizon", which is valuable for ships when the line-of-sight may be only

25479-420: The special case of dispersion-free and uniform media, waves other than sinusoids propagate with unchanging shape and constant velocity. In certain circumstances, waves of unchanging shape also can occur in nonlinear media; for example, the figure shows ocean waves in shallow water that have sharper crests and flatter troughs than those of a sinusoid, typical of a cnoidal wave , a traveling wave so named because it

25650-650: The station's identifier that is used to confirm the station and its operational status. Since these radio signals are broadcast in all directions (omnidirectional) during the day, the signal itself does not include direction information, and these beacons are therefore referred to as non-directional beacons , or NDBs . As the commercial medium wave broadcast band lies within the frequency capability of most RDF units, these stations and their transmitters can also be used for navigational fixes. While these commercial radio stations can be useful due to their high power and location near major cities, there may be several miles between

25821-588: The successful bombardment and capture of the city. This successful landing and capture of Veracruz opened the way for the capture of Mexico City and the end of the war. The U.S. Navy established itself as a player in United States foreign policy through the actions of Commodore Matthew C. Perry in Japan, which resulted in the Convention of Kanagawa in 1854. Naval power played a significant role during

25992-529: The system locally as if it were uniform with the local properties; in particular, the local wave velocity associated with a frequency is the only thing needed to estimate the corresponding local wavenumber or wavelength. In addition, the method computes a slowly changing amplitude to satisfy other constraints of the equations or of the physical system, such as for conservation of energy in the wave. Waves in crystalline solids are not continuous, because they are composed of vibrations of discrete particles arranged in

26163-482: The treaty. The New Deal used Public Works Administration funds to build warships, such as USS  Yorktown  (CV-5) and USS  Enterprise  (CV-6) . By 1936, with the completion of USS  Wasp  (CV-7) , the U.S. Navy possessed a carrier fleet of 165,000 tonnes displacement , although this figure was nominally recorded as 135,000 tonnes to comply with treaty limitations. Franklin Roosevelt ,

26334-505: The turn of the 20th century. Prominent examples were patented by John Stone Stone in 1902 (U.S. Patent 716,134) and Lee de Forest in 1904 (U.S. Patent 771,819), among many other examples. By the early 1900s, many experimenters were looking for ways to use this concept for locating the position of a transmitter. Early radio systems generally used medium wave and longwave signals. Longwave in particular had good long-distance transmission characteristics due to their limited interaction with

26505-501: The two. The pseudo-doppler technique is a phase based DF method that produces a bearing estimate on the received signal by measuring the doppler shift induced on the signal by sampling around the elements of a circular array. The original method used a single antenna that physically moved in a circle but the modern approach uses a multi-antenna circular array with each antenna sampled in succession. The Watson-Watt technique uses two antenna pairs to perform an amplitude comparison on

26676-427: The wave packet, and the spread of the wavenumbers of sinusoids that make up the packet, correspond to the uncertainties in the particle's position and momentum, the product of which is bounded by Heisenberg uncertainty principle . When sinusoidal waveforms add, they may reinforce each other (constructive interference) or cancel each other (destructive interference) depending upon their relative phase. This phenomenon

26847-456: The wave vectors confined to the Brillouin zone . This indeterminacy in wavelength in solids is important in the analysis of wave phenomena such as energy bands and lattice vibrations . It is mathematically equivalent to the aliasing of a signal that is sampled at discrete intervals. The concept of wavelength is most often applied to sinusoidal, or nearly sinusoidal, waves, because in

27018-422: The wave's shape repeats. In other words, it is the distance between consecutive corresponding points of the same phase on the wave, such as two adjacent crests, troughs, or zero crossings . Wavelength is a characteristic of both traveling waves and standing waves , as well as other spatial wave patterns. The inverse of the wavelength is called the spatial frequency . Wavelength is commonly designated by

27189-426: The wave. They are also commonly expressed in terms of wavenumber k (2π times the reciprocal of wavelength) and angular frequency ω (2π times the frequency) as: in which wavelength and wavenumber are related to velocity and frequency as: or In the second form given above, the phase ( kx − ωt ) is often generalized to ( k ⋅ r − ωt ) , by replacing the wavenumber k with a wave vector that specifies

27360-462: The wavelength, more commonly 1 ⁄ 2 – the half-wave dipole is a very common design. For longwave use, this resulted in loop antennas tens of feet on a side, often with more than one loop connected together to improve the signal. Another solution to this problem was developed by the Marconi company in 1905. This consisted of a number of horizontal wires or rods arranged to point outward from

27531-604: The years much as the Commander of the Carrier Air Group/Wing (CAG) does not work for the carrier commanding officer, but coordinates with the ship's CO and staff. Some Marine aviation squadrons, usually fixed-wing assigned to carrier air wings train and operate alongside Navy squadrons; they fly similar missions and often fly sorties together under the cognizance of the CAG. Aviation is where the Navy and Marines share

27702-588: Was a major participant in the Korean and Vietnam Wars , blockaded Cuba during the Cuban Missile Crisis , and, through the use of ballistic missile submarines , became an important aspect of the United States' nuclear strategic deterrence policy. The U.S. Navy conducted various combat operations in the Persian Gulf against Iran in 1987 and 1988, most notably Operation Praying Mantis . The Navy

27873-464: Was equipped with a direction finder (Appleyard 1988). Very few maritime radio navigation beacons remain active today (2008) as ships have abandoned navigation via RDF in favor of GPS navigation. In the United Kingdom a radio direction finding service is available on 121.5 MHz and 243.0 MHz to aircraft pilots who are in distress or are experiencing difficulties. The service is based on

28044-551: Was expended on identifying secret transmitters in the United Kingdom (UK) by direction finding. The work was undertaken by the Radio Security Service (RSS also MI8). Initially three U Adcock HF DF stations were set up in 1939 by the General Post Office. With the declaration of war, MI5 and RSS developed this into a larger network. One of the problems with providing coverage of an area the size of

28215-493: Was extensively involved in Operation Urgent Fury , Operation Desert Shield , Operation Desert Storm , Operation Deliberate Force , Operation Allied Force , Operation Desert Fox and Operation Southern Watch . The U.S. Navy has also been involved in search and rescue/search and salvage operations, sometimes in conjunction with vessels of other countries as well as with U.S. Coast Guard ships. Two examples are

28386-714: Was faced with a two-front war on the seas. It achieved notable acclaim in the Pacific Theater , where it was instrumental to the Allies' successful " island hopping " campaign. The U.S. Navy participated in many significant battles, including the Battle of the Coral Sea , the Battle of Midway , the Solomon Islands Campaign , the Battle of the Philippine Sea , the Battle of Leyte Gulf , and

28557-517: Was largely supplanted in North America by the development of LORAN in the 1970s. Today many NDBs have been decommissioned in favor of faster and far more accurate GPS navigational systems. However the low cost of ADF and RDF systems, and the continued existence of AM broadcast stations (as well as navigational beacons in countries outside North America) has allowed these devices to continue to function, primarily for use in small boats, as an adjunct or backup to GPS. In World War II considerable effort

28728-409: Was not until 1921 US naval aviation truly commenced. During World War I , the U.S. Navy spent much of its resources protecting and shipping hundreds of thousands of soldiers and marines of the American Expeditionary Force and war supplies across the Atlantic in U-boat infested waters with the Cruiser and Transport Force . It also concentrated on laying the North Sea Mine Barrage . Hesitation by

28899-400: Was once the primary aviation navigational aid. ( Range and Direction Finding was the abbreviation used to describe the predecessor to radar .) Beacons were used to mark "airways" intersections and to define departure and approach procedures. Since the signal transmitted contains no information about bearing or distance, these beacons are referred to as non-directional beacons , or NDB in

29070-403: Was successful in a number of engagements and raided many British merchant vessels, but it lost twenty-four of its vessels and at one point was reduced to two in active service. In August 1785, after the Revolutionary War had drawn to a close, Congress had sold Alliance , the last ship remaining in the Continental Navy due to a lack of funds to maintain the ship or support a navy. In 1972,

29241-455: Was symmetrical, and thus identified both the correct degree heading marked on the radio's compass rose as well as its 180-degree opposite. While this information provided a baseline from the station to the ship or aircraft, the navigator still needed to know beforehand if he was to the east or west of the station in order to avoid plotting a course 180-degrees in the wrong direction. By taking bearings to two or more broadcast stations and plotting

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