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46-600: The airport was formerly within Kankan, with the ICAO code of GUXN . The old runway is now a street in the city. The Kankan non-directional beacon (Ident: KN ) is located in the city, 5.4 nautical miles (10.0 km) southwest of the airport. This article about an airport in Guinea is a stub . You can help Misplaced Pages by expanding it . Non-directional beacon A non-directional beacon ( NDB ) or non-directional radio beacon

92-481: A fix of their geographic location on the surface of the Earth. Fixes are computed by extending lines through known navigational reference points until they intersect. For visual reference points, the angles of these lines can be determined by compass ; the bearings of NDB radio signals are found using radio direction finder (RDF) equipment. Plotting fixes in this manner allow crews to determine their position. This usage

138-489: A locator outer marker , or LOM); in Canada, low-powered NDBs have replaced marker beacons entirely. Marker beacons on ILS approaches are now being phased out worldwide with DME ranges or GPS signals used, instead, to delineate the different segments of the approach. German Navy U-boats during World War II were equipped with a Telefunken Spez 2113S homing beacon. This transmitter could operate on 100 kHz to 1500 kHz with

184-471: A DME in a similar installation for the ILS as the outer marker, only in this case, they function as the inner marker. NDB owners are mostly governmental agencies and airport authorities. NDB radiators are vertically polarised. NDB antennas are usually too short for resonance at the frequency they operate – typically perhaps 20 metres length compared to a wavelength around 1000 m. Therefore, they require

230-530: A different angle to the beacon. For ease of visualisation, it can be useful to consider a 90° banked turn, with the wings vertical. The bearing of the beacon as seen from the ADF aerial will now be unrelated to the direction of the aircraft to the beacon. Dip error is sometimes wrongly confused with quadrantal error, which is the result of radio waves being bounced and reradiated by the airframe. Quadrantal error does not affect signals from straight ahead or behind, nor on

276-451: A few moments at low levels to several minutes at high altitude. The ADF may be used to home in on a station. Homing is flying the aircraft on the heading required to keep the needle pointing directly to the 0° (straight ahead) position. To home into a station, tune the station, identify the Morse code signal, then turn the aircraft to bring the ADF azimuth needle to the 0° position. Turn to keep

322-404: A power of 150 W. It was used to send the submarine's location to other submarines or aircraft, which were equipped with DF receivers and loop antennas. NDBs typically operate in the frequency range from 190 kHz to 535 kHz (although they are allocated frequencies from 190 to 1750 kHz) and transmit a carrier modulated by either 400 or 1020 Hz. NDBs can also be collocated with

368-433: A suitable matching network that may consist of an inductor and a capacitor to "tune" the antenna. Vertical NDB antennas may also have a T-antenna , nicknamed a top hat , which is an umbrella-like structure designed to add loading at the end and improve its radiating efficiency. Usually a ground plane or counterpoise is connected underneath the antenna. Apart from Morse code identity of either 400 Hz or 1020 Hz,

414-408: Is a radio beacon which does not include inherent directional information. Radio beacons are radio transmitters at a known location, used as an aviation or marine navigational aid . NDB are in contrast to directional radio beacons and other navigational aids, such as low-frequency radio range , VHF omnidirectional range (VOR) and tactical air navigation system (TACAN). NDB signals follow

460-521: Is at the position. However, using a separate RBI and compass, this requires considerable mental calculation to determine the appropriate relative bearing. To simplify this task, a compass card driven by the aircraft's magnetic compass is added to the RBI to form a radio magnetic indicator (RMI). The ADF needle is then referenced immediately to the aircraft's magnetic heading, which reduces the necessity for mental calculation. Many RMIs used for aviation also allow

506-479: Is equipped with ILS, it is called a precision approach runway. NDBs are most commonly used as markers or "locators" for an instrument landing system (ILS) approach or standard approach. NDBs may designate the starting area for an ILS approach or a path to follow for a standard terminal arrival route , or STAR. In the United States, an NDB is often combined with the outer marker beacon in the ILS approach (called

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552-434: Is important in situations where other navigational equipment, such as VORs with distance measuring equipment (DME), have failed. In marine navigation, NDBs may still be useful should Global Positioning System (GPS) reception fail. To determine the distance to an NDB station, the pilot uses this method: A runway equipped with NDB or VOR (or both) as the only navigation aid is called a non-precision approach runway; if it

598-415: Is less than 50 watts ; "medium" from 50 W to 2,000 W; and "high" at more than 2,000 W. There are four types of non-directional beacons in the aeronautical navigation service: The last two types are used in conjunction with an instrument landing system (ILS). NDB navigation consists of two parts — the automatic direction finder (ADF) equipment on the aircraft that detects an NDB's signal, and

644-413: Is less than 50 watts; "medium" from 50 W to 2,000 W; and "high" at more than 2,000 W. The ADF indicators are a kind of navigational display consisting of a dial and a needle that rotates around the dial and points to the beacon. This needle suggests the "to" bearing of the beacon, and to fly the "from" bearing, 180° needs to be added or subtracted from the reading. There are two types of ADF indicators:

690-478: Is the case, Flight inspection organizations periodically check critical parameters with properly equipped aircraft to calibrate and certify NDB precision. The ICAO minimum accuracy for NDBs is ±5° Besides their use in aircraft navigation, NDBs are also popular with long-distance radio enthusiasts ( DXers ). Because NDBs are generally low-power (usually 25 watts, some can be up to 5 kW), they normally cannot be heard over long distances, but favorable conditions in

736-641: The DXing hobby. In North America, the NDB band is from 190 to 435 kHz and from 510 to 530 kHz. In Europe, there is a longwave broadcasting band from 150 to 280 kHz, so the European NDB band is from 280 kHz to 530 kHz with a gap between 495 and 505 kHz because 500 kHz was the international maritime distress (emergency) frequency . The beacons that transmit between 510 kHz and 530 kHz can sometimes be heard on AM radios that can tune below

782-436: The ionosphere can allow NDB signals to travel much farther than normal. Because of this, radio DXers interested in picking up distant signals enjoy listening to faraway NDBs. Also, since the band allocated to NDBs is free of broadcast stations and their associated interference, and because most NDBs do little more than transmit their Morse code callsign, they are very easy to identify, making NDB monitoring an active niche within

828-436: The "fixed azimuth dial" type with 0° always represents the aircraft nose, and 180° always represents the aircraft tail; and the type with rotating dials that can be rotated to align the azimuth with the aircraft heading. As an aircraft nears an NDB station, the ADF becomes increasingly sensitive, small lateral deviations result in large deflections of the needle which sometimes shows erratic left/right oscillations. Ideally, as

874-426: The ADF heading indicator pointing directly ahead. Homing is regarded as poor piloting technique because the aircraft may be blown significantly or dangerously off-course by a cross-wind, and will have to fly further and for longer than the direct track. The ADF may also be used to track a desired course using an ADF and allowing for winds aloft, winds which may blow the aircraft off-course. Good pilotage technique has

920-416: The ADF shows relative angle of the transmitter with respect to the aircraft, an RMI display incorporates a compass card, actuated by the aircraft's compass system, and permits the operator to read the magnetic bearing to or from the transmitting station, without resorting to arithmetic. Most RMI's incorporate two direction needles. Often one needle (the thicker, double-barred needle) is connected to an ADF and

966-499: The LW band between 190 – 535 kHz. Like RDF ( Radio Direction Finder ) units, most ADF receivers can also receive medium wave (AM) broadcast stations, though these are less reliable for navigational purposes. The operator tunes the ADF receiver to the correct frequency and verifies the identity of the beacon by listening to the Morse code signal transmitted by the NDB. On marine ADF receivers,

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1012-544: The NDB and are charted in brown on sectional charts. Green and red airways are plotted east and west, while amber and blue airways are plotted north and south. As of September 2022, only one colored airway is left in the continental United States, located off the coast of North Carolina and is called G13 or Green 13. Alaska is the only other state in the United States to make use of the colored airway systems. Pilots follow these routes by tracking bearings across various navigation stations, and turning at some. While most airways in

1058-479: The NDB may broadcast: Navigation using an ADF to track NDBs is subject to several common effects: While pilots study these effects during initial training, trying to compensate for them in flight is very difficult; instead, pilots generally simply choose a heading that seems to average out any fluctuations. Radio-navigation aids must keep a certain degree of accuracy, given by international standards, Federal Aviation Administration (FAA), ICAO, etc.; to assure this

1104-487: The NDB transmitter. The ADF can also locate transmitters in the standard AM medium wave broadcast band (530 kHz to 1700 kHz at 10 kHz increments in the Americas, 531 kHz to 1602 kHz at 9 kHz increments in the rest of the world). ADF equipment determines the direction or bearing to the NDB station relative to the aircraft by using a combination of directional and non-directional antennae to sense

1150-408: The NDB. Similarly, the aircraft will track directly away from the NDB if the needle is maintained on the 180 degree mark. With a crosswind, the needle must be maintained to the left or right of the 0 or 180 position by an amount corresponding to the drift due to the crosswind. The formula to determine the compass heading to an NDB station (in a no wind situation) is to take the relative bearing between

1196-659: The United States are based on VORs, NDB airways are common elsewhere, especially in the developing world and in lightly populated areas of developed countries, like the Canadian Arctic , since they can have a long range and are much less expensive to operate than VORs. All standard airways are plotted on aeronautical charts , such as the United States sectional charts , issued by the National Oceanic and Atmospheric Administration (NOAA). NDBs have long been used by aircraft navigators , and previously mariners, to help obtain

1242-423: The aircraft and the station, and add the magnetic heading of the aircraft; if the total is greater than 360 degrees, then 360 must be subtracted. This gives the magnetic bearing that must be flown: (RB + MH) mod 360 = MB. When tracking to or from an NDB, it is also usual that the aircraft track on a specific bearing. To do this it is necessary to correlate the RBI reading with the compass heading. Having determined

1288-440: The aircraft overflies the beacon, the needle swings rapidly from directly ahead to directly behind. This indicates station passage and provides an accurate position fix for the navigator. Less accurate station passage, passing slightly to one side or another, is shown by slower (but still rapid) swinging of the needle. The time interval from the first indications of station proximity to positive station passage varies with altitude —

1334-696: The aviation industry. Airservices Australia began shutting down a number of ground-based navigation aids in May 2016, including NDBs, VORs and DMEs. In the United States as of 2017, there were more than 1,300 NDBs, of which fewer than 300 were owned by the Federal Government. The FAA had begun decommissioning stand-alone NDBs. As of April 2018, the FAA had disabled 23 ground-based navaids including NDBs, and plans to shut down more than 300 by 2025. The FAA has no sustaining or acquisition system for NDBs and plans to phase out

1380-457: The beacon, or may also use the magnetic compass and calculate the direction from the beacon (the radial ) at which their aircraft is located. Unlike the RDF, the ADF operates without direct intervention, and continuously displays the direction of the tuned beacon. Initially, all ADF receivers, both marine and aircraft versions, contained a rotating loop or ferrite loopstick aerial driven by a motor which

1426-403: The beginning of the medium wave (MW) broadcast band. However, reception of NDBs generally requires a radio receiver that can receive frequencies below 530 kHz. Often "general coverage" shortwave radios receive all frequencies from 150 kHz to 30 MHz, and so can tune to the frequencies of NDBs. Specialized techniques (receiver preselectors, noise limiters and filters) are required for

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1472-474: The curvature of the Earth , so they can be received at much greater distances at lower altitudes, a major advantage over VOR. However, NDB signals are also affected more by atmospheric conditions, mountainous terrain, coastal refraction and electrical storms, particularly at long range. The system, developed by United States Army Air Corps (USAAC) Captain Albert Francis Hegenberger , was used to fly

1518-506: The device to display information from a second radio tuned to a VOR station; the aircraft can then fly directly between VOR stations (so-called "Victor" routes) while using the NDBs to triangulate their position along the radial, without the need for the VOR station to have a collocated distance measuring equipment (DME). This display, along with the omni bearing indicator (OBI) for VOR/ILS information,

1564-459: The direction in which the combined signal is strongest. This bearing may be displayed on a relative bearing indicator (RBI). This display looks like a compass card with a needle superimposed, except that the card is fixed with the 0 degree position corresponding to the centreline of the aircraft. In order to track toward an NDB (with no wind), the aircraft is flown so that the needle points to the 0 degree position. The aircraft will then fly directly to

1610-404: The drift, the aircraft must be flown so that the compass heading is the required bearing adjusted for drift at the same time as the RBI reading is 0 or 180 adjusted for drift. An NDB may also be used to locate a position along the aircraft's current track (such as a radial path from a second NDB or a VOR). When the needle reaches an RBI reading corresponding to the required bearing, then the aircraft

1656-473: The existing NDBs through attrition, citing decreased pilot reliance on NDBs as more pilots use VOR and GPS navigation. Radio magnetic indicator An automatic direction finder ( ADF ) is a marine or aircraft radio-navigation instrument that automatically and continuously displays the relative bearing from the ship or aircraft to a suitable radio station. ADF receivers are normally tuned to aviation or marine NDBs ( Non-Directional Beacon ) operating in

1702-436: The motorized ferrite-bar antenna atop the unit (or remotely mounted on the masthead) would rotate and lock when reaching the null of the desired station. A centerline on the antenna unit moving atop a compass rose indicated in degrees the bearing of the station. On aviation ADFs, the unit automatically moves a compass-like pointer (RMI) to show the direction of the beacon. The pilot may use this pointer to home directly towards

1748-420: The other (generally thin or single-barred) is connected to a VOR . Some models allow the operator to select which needle is connected to each navigation radio. There is great variation between models, and the operator must take care that their selection displays information from the appropriate ADF and VOR. This instrument display can replace a magnetic compass display in the instrument panel, but not necessarily

1794-413: The pilot calculate a correction angle that exactly balances the expected crosswind. As the flight progresses, the pilot monitors the direction to or from the NDB using the ADF, adjusts the correction as required. A direct track will yield the shortest distance and time to the ADF location. A radio magnetic indicator ( RMI ) is an alternate ADF display providing more information than a standard ADF. While

1840-552: The reception of very weak signals from remote beacons. The best time to hear NDBs that are very far away is the last three hours before sunrise. Reception of NDBs is also usually best during the fall and winter because during the spring and summer, there is more atmospheric noise on the LF and MF bands. As the adoption of satellite navigation systems such as GPS progressed, several countries began to decommission beacon installations such as NDBs and VOR. The policy has caused controversy in

1886-422: The signal, and provide the heading to the station using a direction indicator. In flight, the ADF's RMI or direction indicator will always point to the broadcast station regardless of aircraft heading. Dip error is introduced, however, when the aircraft is in a banked attitude, as the needle dips down in the direction of the turn. This is the result of the loop itself banking with the aircraft and therefore being at

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1932-420: The station that points in a specific direction, such as 270 degrees (due west). NDB bearings provide a charted, consistent method for defining paths aircraft can fly. In this fashion, NDBs can, like VORs, define airways in the sky. Aircraft follow these pre-defined routes to complete a flight plan . Airways are numbered and standardized on charts. Colored airways are used for low to medium frequency stations like

1978-657: The wingtips. The further from these cardinal points and the closer to the quadrantal points (i.e. 45°, 135°, 225° and 315° from the nose) the greater the effect, but quadrantal error is normally much less than dip error, which is always present when the aircraft is banked. ADF receivers can be used to determine current position, track inbound and outbound flight path, and intercept a desired bearing. These procedures are also used to execute holding patterns and non-precision instrument approaches. Non-directional beacons in North America are classified by power output: "low" power rating

2024-688: The world's first instrument approach on May 9, 1932. NDBs used for aviation are standardised by the International Civil Aviation Organization (ICAO) Annex 10 which specifies that NDBs be operated on a frequency between 190  kHz and 1750 kHz, although normally all NDBs in North America operate between 190 kHz and 535 kHz. Each NDB is identified by a one, two, or three-letter Morse code callsign. In Canada, privately owned NDB identifiers consist of one letter and one number. Non-directional beacons in North America are classified by power output: "low" power rating

2070-402: Was controlled by the receiver. Like the RDF, a sense antenna verified the correct direction from its 180-degree opposite. More modern aviation ADFs contain a small array of fixed aerials and use electronic sensors to deduce the direction using the strength and phase of the signals from each aerial. The electronic sensors listen for the trough that occurs when the antenna is at right angles to

2116-411: Was one of the primary radio navigation instruments prior to the introduction of the horizontal situation indicator (HSI) and subsequent digital displays used in glass cockpits . The principles of ADFs are not limited to NDB usage; such systems are also used to detect the locations of broadcast signals for many other purposes, such as finding emergency beacons. A bearing is a line passing through

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