462:
121:
886:
605:
128:
1035:
Decca Flight Log moving map display to further improve ease of navigation. In spite of these advantages, the RTCA ultimately chose VOR/DME for two primary reasons; VOR offered coverage over about the same range as Decca, about 200 miles, but did so with a single transmitter instead of Decca's four, and Decca's frequencies proved susceptible to interference from static due to lightning, while VOR's higher frequencies were not quite as sensitive.
225:
747:
22:
187:
180 transmitting stations using "chains" of three or four transmitters each to allow position fixing by plotting intersecting electronic lines. Decca's primary use was for ship navigation in coastal waters, offering much better accuracy than the competing LORAN system. Fishing vessels were major post-war users, but it was also used on some aircraft, including a very early (1949) application of
622:
several advancements in the art that would prove useful. He initially imagined the system being used for aircraft testing, specifically the accurate calculation of ground speed. Some experiments were carried out in
California in 1938, selecting frequencies with harmonic "beats" that would allow for station identification in a network of transmitters. Both the
765:; at its peak it was deployed in many of the world's major shipping areas. More than 15,000 receiving sets were in use aboard ships in 1970. There were 4 chains around England, 1 in Ireland and 2 in Scotland, 12 in Scandinavia (5 each in Norway and Sweden and 1 each in Denmark and Finland), a further 4 elsewhere in northern Europe and 2 in Spain.
289:, the difference in phase between the two signals is constant along a hyperbolic path. If two stations transmit on the same frequency, it is impossible for the receiver to separate them. Instead, each chain was allocated a nominal frequency, known as 1f, and each station in the chain transmitted at a harmonic of this base frequency, as follows:
1026:
as much energy as normal chain stations. Given that the length of the chain baselines did not change, and were relatively short, at long distance the signal offered almost no accuracy. Instead, Dectra operated as a track system; aircraft would navigate by keeping themselves within the signal defined by a particular Decca lane.
868:(1 chain with stations in Qatar and the United Arab Emirates and a second chain in the north of the Gulf with stations in Iran) and the Bahamas (1 chain). Four chains were planned for Nigeria but only two were built and these did not enter into public service. Two chains in Vietnam were used during the
1075:
A further application of the Decca system was implemented by the U.S. Navy in the late 1950s and early 1960s for use in the Tongue of the Ocean/Eleuthera Sound area near The
Bahamas, separating the islands of Andros and New Providence. The application was for sonar studies made possible by the unique
856:
This situation was exacerbated by the workload problems of the Air
Traffic Controllers Association (ATCA), under its executive director Francis McDermott, whose members were forced to use radar data on aircraft positions, relaying those positions by radio to the aircraft from their control locations.
551:
As well as transmitting the Decca frequencies of 5f, 6f, 8f and 9f, an 8.2f signal, known as Orange, was also transmitted. The beat frequency between the 8.0f (Red) and 8.2f (Orange) signals allowed a 0.2f signal to be derived and so resulted in a hyperbolic pattern in which one cycle (360°) of phase
532:
The lanes were numbered 0 to 23 for red, 30 to 47 for green and 50 to 79 for purple. The zones were labelled A to J, repeating after J. A Decca position coordinate could thus be written: Red I 16.30; Green D 35.80. Later receivers incorporated a microprocessor and displayed a position in latitude and
485:, with 18 green, 24 red, or 30 purple lanes in each zone. This meant that on the baseline (the straight line between the Master and its Slave) the zone width was the same for all three patterns of a given chain. Typical lane and zone widths on the baseline are shown in the table below (for chain 5B):
1025:
Unlike the Delrac system, Dectra was essentially the normal Decca
Navigator system with the modification of several existing transmitter sites. These were located at the East Newfoundland and Scottish chains, which were equipped with larger antennas and high-power transmitters, broadcasting 20 times
852:
This chain installation was considered highly controversial at the time, for political reasons. This led to the U.S. Coast Guard, under instructions from the
Treasury Department to which it reported, banning the use of Decca receivers in ships entering New York harbour for fear that the system might
477:
that indicated the phase difference for each pattern. Each
Decometer drove a second indicator that counted the number of lanes traversed – each 360 degrees of phase difference was one lane traversed. In this way, assuming the point of departure was known, a more or less distinct location could
276:
Receivers determined their location by measuring the phase difference from two or more of the patterns from the displays. They could then look at the chart to find where the two closest charted hyperbolas crossed. The accuracy of this measurement was improved by choosing the set of two patterns that
1050:. The Omnitrac could take inputs from Decca (and Dectra), Loran-C, VOR/DME, an air data computer and doppler radars and combine them all to produce a lat/long output along with bearing, distance-to-go, bearing and an autopilot coupling. Their efforts to standardize this were eventually abandoned as
1034:
system that ultimately won the competition offered navigation over perhaps a 200-mile radius, and could not offer a solution to the long-distance problem. Additionally, as the Decca system provided an X and Y location, as opposed to the angle-and-range VOR/DME, Decca proposed offering it with their
876:
near OsnabrĂĽck and there were two Slaves. The purpose of this chain was to provide accurate air navigation for the corridor between
Western Germany and Berlin in the event that a mass evacuation of allied personnel may be required. In order to maintain secrecy, frequencies were changed at irregular
848:
and did not suffer the slant-range errors that create problems with VOR/DME close to the transmitters. The Decca installations in the New York
Airways helicopters included the unique Decca 'roller map' displays that enabled the pilot to see his or her position at a glance, a concept infeasible with
252:
difference of the signals from the master and one of the secondaries, produced a relative phase measure that was presented on a clock-like display. The phase difference was caused by the relative distance between the stations as seen by the receiver. As the receiver moves these distances change and
1071:
Another application was developed by the Bendix
Pacific division of Bendix Corporation, with offices in North Hollywood, California, but not deployed: PFNS—Personal Field Navigation System—that would enable individual soldiers to ascertain their geographic position, long before this capability was
186:
landings. The Allied forces needed an accurate system not known to the
Germans and thus free of jamming. After the war, it came off the secret list and was commercially developed by the Decca Company and deployed around UK and later used in many areas around the world. At its peak there were about
547:
The nominally continuous wave transmissions were in fact divided into a 20-second cycle, with each station in turn simultaneously transmitting all four Decca frequencies (5f, 6f, 8f and 9f) in a phase-coherent relationship for a brief period of 0.45 seconds each cycle. This transmission, known as
1083:
The 'low frequency' signalling of the Decca system also permitted its use on submarines. One 'enhancement' of the Decca system was to offer the potential of keying the signal, using Morse code, to signal the onset of nuclear war. This option was never taken up by the UK government. Messages were
1079:
An interesting characteristic of the Decca VLF signal discovered on BOAC, later British Airways, test flights to Moscow, was that the carrier switching could not be detected even though the carrier could be received with sufficient strength to provide navigation. Such testing, involving civilian
912:
A significant amount of income from the Decca system was due to the receivers being leased to users, not sold outright. This guaranteed predictable annual income. When the patents on the original technology lapsed in the early 1980s, new receivers were quickly built by a number of companies. In
737:
area to verify receiver accuracy. In the car installation, it was found possible to navigate within an individual traffic lane. The company entertained high hopes that the system could be used in aircraft, to permit much more precise navigation in the critical airspace around airports and urban
1067:
for detailed mapping and surveying of coasts and harbours. The Hi-Fix equipment was leased for a period with temporary chains established to provide coverage of the area required, Hi-Fix was commercialised by Racal Survey in the early 1980s. An experimental chain was installed with coverage of
621:
that put his career on hold for a period of two years. During this period he had the idea of position fixing by means of phase comparison of continuous wave transmissions. This was not the first such system, but O'Brien apparently developed his version without knowledge of the others, and made
595:
this range and accuracy may appear poor, in its day the Decca system was one of the few, if not the only, position fixing system available to many mariners. Since the need for an accurate position is less when the vessel is further from land, the reduced accuracy at long ranges was not a great
587:
By day these errors could range from a few meters on the baseline up to a nautical mile at the edge of coverage. At night, skywave errors were greater and, on receivers without multipulse capabilities, it was not unusual for the position to jump a lane, sometimes without the navigator knowing.
244:
and three (occasionally two) secondary stations, termed Red, Green and Purple. Ideally, the secondaries would be positioned at the vertices of an equilateral triangle with the master at the centre. The baseline length, that is, the master-secondary distance, was typically 60–120 nautical miles
681:
in January 1944 to test a wide variety of upgrades and production equipment. By this time the competing Gee system was known to the Admiralty and the two systems were tested head-to-head under the code names QM and QH. QM was found to have better sea-level range and accuracy, which led to its
1017:
effort, began the process of introducing a standard long-range radio navigation system for aviation use. Decca proposed a system that could offer both high-accuracy at short ranges and trans-Atlantic navigation with less accuracy, using a single receiver. The system was known as
1000:
system, was introduced in 1954, proposing 28 stations that provided worldwide coverage. The system was predicted to offer 10 miles (16,000 m) accuracy at 2,000 miles (3,200 km) range 95% of the time. Further development was ended in favour of the Dectra system.
1068:
central London and receivers placed in London buses and other vehicles to demonstrate an early vehicle location and tracking system. Each vehicle would report its location automatically via a conventional VHF two-way radio link, the data added to a voice channel.
449:. Since the wavelength of the common frequency was small compared with the distance between the Master and Slave stations there were many possible lines of position for a given phase difference, and so a unique position could not be arrived at by this method.
853:
create a de facto standard (as it had become in other areas of the world). It also served to protect the marketing interests of the Hoffman Electronics division of ITT, a principal supplier of VOR/DME systems, that Decca might have been poised to usurp.
861:, that—according to some experts—could have been avoided if the aircraft had been Decca-equipped and could not only have determined their positions more precisely but would not have suffered from the rho-theta position errors inherent in VOR/DME.
788:
area. A fourth chain covering eastern Newfoundland was added in 1958. When meetings in Montreal in 1958 led to VOR and DME being selected as the standard aviation navigation systems, the Montreal system was moved eastward to cover the
1029:
The main advantage of Dectra compared to other systems being proposed for the RTCA solution was that it could be used for both medium-range navigation over land, as well as long-range navigation over the Atlantic. In comparison, the
917:) introduced receivers that could be purchased outright, and were much smaller and easier to use than the current Decca counterparts. The "ap" versions directly output the longitude and latitude to two decimals (originally in datum
1038:
Decca continued to propose that Dectra be used for the long-range role. In 1967 they installed another transmitter in Iceland to provide ranging along the Scotland-Newfoundland track, with a second proposed to be installed on the
206:
system to civilian use in 1974 offered stiff competition, but Decca was well established by this time and continued operations to 2000. Decca Navigator was eventually replaced, along with Loran and similar systems, by the
909:, the UK weapons and communications company, acquired Decca in 1980. Merging Decca's radar assets with their own, Racal began selling off the other portions of the company, including avionics and Decca Navigator.
131:
The display panel of a Decca Navigator Mk 12 (ca. 1962). Decca position coordinates were directly displayed by four decometers and these were plotted on a conventional chart that had been over-printed with Decca
921:
only) instead of using the "deco meter" displays, offering accuracy better than ±9.3 m, much better than the Decca units. This also eliminated the need for the special charts printed with Decca lanes and zones.
810:
1062:
A more accurate system named Hi-Fix was developed using signalling in the 1.6 MHz range. It was used for specialised applications such as precision measurements involved with oil-drilling and by the
452:
Other receivers, typically for aeronautical applications, divided the transmitted frequencies down to the basic frequency (1f) for phase comparison, rather than multiplying them up to the LCM frequency.
232:
The phase difference between the signals received from stations A (Master) and B (Secondary) is constant along each hyperbolic curve. The foci of the hyperbolas are at the transmitting stations, A and B.
664:
in April 1943 at 70/130 kHz. It was decided that the original frequencies were not ideal, and a new system using a 14 kHz inter-signal spacing was selected. This led to the common 5, 6, 8 and
445:
It was phase comparison at this common frequency that resulted in the hyperbolic lines of position. The interval between two adjacent hyperbolas on which the signals are in phase was called a
698:
receivers. The receiver consisted of an electronics unit with two dials and was known to its operators as the "Blue Gasmeter Job". A Decca chain was set up, consisting of a master station at
925:
Decca sued ap for infringement and, in the ensuing court battle, Decca lost the monopoly. That signalled the beginning of the end for the company. Income dwindled and eventually, the UK
563:
During daylight, ranges of around 400 nautical miles (740 km) could be obtained, reducing at night to 200 to 250 nautical miles (460 km), depending on propagation conditions.
147:
system that allowed ships and aircraft to determine their position by using radio signals from a dedicated system of static radio transmitters. The system used phase comparison of two
645:
system, being carried out by Watt's group). However, in October 1941 the British Admiralty Signal Establishment (ASE) became interested in the system, which was then classified as
163:. This made it much easier to design receivers using 1940s electronics, and operation was simplified by giving a direct readout of Decca coordinates without the complexity of a
872:
for helicopter navigation, with limited success. During the Cold War period, following WWII, the R.A.F. established a confidential chain in Germany. The Master station was in
1220:
1093:
864:
Other chains were established in Japan (6 chains); Namibia and South Africa (5 chains); India and Bangladesh (4 chains); North-West Australia (2 chains); the
1043:. They also installed Dectra receivers with Omnitrac computers and a lightweight version of the Flight Log on a number of commercial airliners, notably a
840:
on Park Avenue. Use of Decca was essential because its signals could be received down to sea level, were not subject to the line-of-sight limitations of
351:
The frequencies given are those for Chain 5B, known as the English Chain, but all chains used similar frequencies between 70 kHz and 129 kHz.
544:
provided an automatic method of lane and zone identification by using the same phase comparison techniques described above on lower frequency signals.
694:
in February/March 1944. The success of the trials and the relative ease of use and accuracy of the system resulted in Decca receiving an order for 27
1221:"UNITED AIR LINES, INC, DC-8, N 8013U, AND TRANS WORLD AIRLINES, INC., CONSTELLATION 1049A, N 6907C, NEAR STATEN ISLAND, NEW YORK, DECEMBER 16, 1960"
256:
If one selects a particular phase difference, say 30 degrees, and plots all the locations where that phase difference occurs, the result is a set of
548:
Multipulse, allowed the receiver to extract the 1f frequency and so to identify the lane that the receiver was in (to a resolution of a zone).
988:
Work on this concept continued, and in 1951 a modified version was presented that offered navigation over very wide areas. This was known as
961:
In the immediate post-war era, Decca began studying a long-range system like Decca, but using much lower frequencies to enable reception of
1309:
Blanchard, Walter (September 1991). "Hyperbolic Airborne Radio Navigation Aids — A Navigator's View of their History and Development".
1010:
86:
354:
Decca receivers multiplied the signals received from the Master and each Slave by different values to arrive at a common frequency (
816:
In the late 1950s an experimental Decca chain was set up in the United States, in the New York area, to be used for navigating the
58:
1084:
clandestinely sent, however, between Decca stations thereby bypassing international telephone calls, especially in non-UK chains.
39:
997:
65:
825:
897:
The headquarters of Decca Navigator were at New Malden, Surrey, just off the Kingston by-pass. There was a Decca School, at
829:
269:. As there were three secondaries there were three patterns, also termed Red, Green and Purple. The patterns were drawn on
1385:
641:
reviewed the system but he did not follow it up, deeming it too easily jammed (and likely due to the existing work on the
637:
in England. In 1939 O’Brien sent him details of the system so it could be put forward to the British military. Initially
72:
461:
105:
54:
1418:
858:
776:
in 1956 as part of a joint Canada-US Navy surveying program. This led to commercial deployments the next year in
726:
and to sweep the minefields in the planned areas. The swept areas were marked with buoys in preparation for the
817:
43:
1346:
The Decca Navigator - Principles and Performance of the System, The Decca Navigator Company Limited, July 1976
1352:
The Decca Navigator System on D-Day, 6 June 1944, An Acid Test, Commander Hugh St. A. Malleson, R.N. (Ret.)
970:
937:
893:
Decca receiver Mk II from the 1980s that could be purchased instead of leased. It could store 25 waypoints.
845:
236:
The Decca Navigator System consisted of individual groups of land-based radio transmitters organised into
761:
the Decca Navigator Co. Ltd. was formed (1945) and the system expanded rapidly, particularly in areas of
751:
1051:
1413:
1120:
841:
805:
had oil tanker traffic used the area, but this never came to be. Another was briefly set up covering
690:
A three-station trial was held in conjunction with a large-scale assault and landing exercise in the
592:
208:
965:
at long distances. In February 1946 the company proposed a system with two main stations located at
79:
1125:
926:
555:
Assuming that one's position was known to this accuracy, this gave an effectively unique position.
1360:
Navigation Systems: A Survey of Modern Electronic Aids, ed. G.E. Beck, van Nostrand Reinhold, 1971
1187:
1098:
32:
355:
141:
992:, short for "Decca Long Range Area Cover". A further development, including features of the
794:
8:
993:
941:
977:(today part of Canada). Together, these stations would provide navigation over the main
1326:
978:
638:
188:
1330:
940:
ceased Decca transmissions at midnight on 31 March 2000. The Irish chain provided by
833:
802:
727:
286:
261:
1349:
Night Passage to Normandy, Lieutenant-Commander Oliver Dawkins, R.N.V.R, Decca, 1969
985:
would provide general ranging information to measure progress along the main track.
859:
collision of a Douglas DC8 and a Lockheed Constellation over Staten Island, New York
1397:
1318:
1110:
936:
A ruling from the European Union forced the UK government to withdraw funding. The
837:
836:
in the Borough of Queens, nearer to Manhattan, and a site on the top of the (then)
821:
790:
642:
164:
156:
144:
1391:
966:
723:
722:
and, on 5 June 1944, 17 of these ships used it to accurately navigate across the
466:
120:
797:, and the western Newfoundland chain was later repositioned to better cover the
1423:
762:
711:
677:-like extension, but never developed. A follow-up test was carried out in the
270:
241:
1322:
813:. The last Canadian chain shut down in 1986, after Loran-C became widespread.
1407:
930:
634:
469:
Decca Chart of the Thames Estuary, marked with red and green lanes and zones.
249:
148:
1370:
733:
After the initial ship tests, Decca conducted tests in cars, driving in the
253:
those changes are represented by the movement of the hands on the displays.
1080:
aircraft, is quite common and may well not be in the knowledge of a pilot.
1047:
974:
865:
806:
798:
773:
758:
618:
196:
179:
1375:
944:
continued transmitting until 19 May 2000. Japan continued operating their
885:
869:
781:
777:
707:
691:
654:
277:
resulted in the lines crossing at as close to a right angle as possible.
248:
Each station transmitted a continuous wave signal that, by comparing the
171:
1355:
Hyperbolic Radionavigation Systems, Compiled by Jerry Proc VE3FAB, 2007
604:
127:
1064:
699:
175:
1338:
1072:
made possible by the satellite-based GPS (Global Positioning System).
224:
873:
824:. These helicopters were operating from the principal local airports—
678:
661:
627:
623:
257:
192:
152:
714:
as part of the deception that the invasion would be focussed on the
21:
1130:
945:
785:
650:
1356:
746:
1115:
1031:
982:
962:
933:
take responsibility for operating the system in the early 1990s.
898:
769:
734:
703:
674:
580:
203:
1380:
1040:
715:
633:
O’Brien's friend, Harvey F. Schwarz, was chief engineer of the
906:
902:
768:
Canada was another early user, with branch offices set up in
183:
160:
913:
particular, Aktieselskabet Dansk Philips ('Danish Philips',
669:
frequencies, used throughout the life of the Decca system. 7
657:, at frequencies of 305/610 kHz, on 16 September 1942.
630:
considered the idea too complicated and work ended in 1939.
182:
for the vital task of clearing the minefields to enable the
1044:
1014:
948:
chain until March 2001, the last Decca chain in operation.
918:
608:
Decca Navigator Mk. 21, with the Decometer dials prominent.
1279:
1277:
1275:
1262:
1260:
1258:
1245:
1243:
1241:
1170:
1168:
1166:
1153:
1151:
905:, where employees were sent on courses from time to time.
718:
area. 21 minesweepers and other vessels were fitted with
273:
as a set of hyperbolic lines in the appropriate colour.
1295:"Dectra in Iceland", Decca Navigator News, October 1967
1272:
1255:
1238:
1163:
1148:
473:
Early Decca receivers were fitted with three rotating
857:
An example of the problem, cited by experts, was the
240:
of three or four stations. Each chain consisted of a
1381:
Decca Navigator Spain by Santiago Insua (in Spanish)
801:. A series of chains was also proposed to cover the
772:
in 1953. The first chain was installed in southwest
617:
In 1936 William J. O'Brien, an engineer, contracted
211:
in 2000, when that became available for public use.
280:
46:. Unsourced material may be challenged and removed.
1396:is available for free viewing and download at the
880:
780:and an inland system for air traffic in the busy
649:. The first marine trials were conducted between
1405:
981:between London and New York. A third station in
710:. A fourth decoy transmitter was located in the
573:Angle of cut of the hyperbolic lines of position
358:, LCM) for each Master/Slave pair, as follows:
660:Further trials were conducted in the northern
191:. The system was deployed extensively in the
811:International Field Year for the Great Lakes
1225:Plane and Train Wrecks | Online Collections
738:centres where traffic density was highest.
1011:Radio Technical Commission for Aeronautics
214:
155:, as opposed to pulse timing systems like
1308:
1283:
1266:
1249:
1174:
1157:
195:and was used by helicopters operating to
170:The system was invented and developed by
106:Learn how and when to remove this message
884:
745:
741:
603:
460:
223:
174:in the UK. It was first deployed by the
126:
119:
1386:Decca Navigator Station Zeven (Germany)
1087:
1054:began to be installed for these needs.
1406:
1337:A modified version is = Jerry Proc,
951:
591:Although in the days of differential
558:
1376:A virtual tour of a Decca Main Chain
1371:Decca Navigator System by Jerry Proc
1076:characteristics of the ocean floor.
44:adding citations to reliable sources
15:
13:
750:Decca receiver, Mk.51 seen in the
456:
285:When two stations transmit at the
14:
1435:
1364:
685:
579:Propagation errors (for example,
202:The opening of the more accurate
281:Detailed principles of operation
20:
1393:STAFF FILM REPORT 66-19A (1966)
1302:
881:Decca, Racal, and the closedown
552:difference equates to 5 zones.
31:needs additional citations for
1289:
1213:
1198:
1180:
229:The Decca Navigator principle.
1:
1136:
536:
167:and highly skilled operator.
1192:Decca Navigator (Canada) Ltd
1141:
971:Gander International Airport
938:general lighthouse authority
481:The lanes were grouped into
7:
1194:. Canada Company Directory.
1104:
1052:inertial navigation systems
1022:, short for "Decca Track".
1013:(RTCA), as part of a wider
752:National Museum of Scotland
219:
151:signals between 70 and 129
10:
1440:
612:
599:
566:The accuracy depended on:
1323:10.1017/S0373463300010092
1311:The Journal of Navigation
1188:"Corporation Information"
1121:Omega (navigation system)
1057:
1004:
956:
1126:Local positioning system
55:"Decca Navigator System"
1205:"Decca Marine Canada".
1099:Zeven DECCA-transmitter
1009:In the early 1960s the
929:stepped in, having the
215:Principles of operation
1419:Navigational equipment
1094:Puckeridge DECCA tower
931:lighthouse authorities
894:
754:
609:
470:
287:phase-locked frequency
233:
138:Decca Navigator System
133:
124:
927:Ministry of Transport
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749:
742:Commercial deployment
607:
464:
356:least common multiple
227:
130:
123:
1207:Decca Navigator News
1088:Special DECCA towers
795:Gulf of St. Lawrence
635:Decca Record company
523:Zones (all patterns)
40:improve this article
994:General Post Office
942:BĂłrd Iascaigh Mhara
720:Admiralty Outfit QM
696:Admiralty Outfit QM
673:was reserved for a
647:Admiralty Outfit QM
576:Instrumental errors
245:(110–220 km).
189:moving map displays
979:great circle route
952:Other applications
895:
755:
639:Robert Watson-Watt
610:
570:Width of the lanes
559:Range and accuracy
494:Width on Baseline
471:
234:
134:
125:
1341:, 14 January 2001
1209:. September 1976.
834:LaGuardia Airport
803:Northwest Passage
763:British influence
757:After the end of
728:Normandy Landings
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529:
443:
442:
379:Common Frequency
376:Master Multiplier
349:
348:
262:lines of position
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1414:Radio navigation
1398:Internet Archive
1339:"The GEE System"
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1111:GEE (navigation)
828:on Long Island,
826:Idlewild Airport
822:New York Airways
809:in 1971 for the
791:Anticosti Island
735:Kingston By-Pass
488:
487:
370:Slave Multiplier
361:
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301:Frequency (kHz)
292:
291:
165:cathode ray tube
145:radio navigation
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1390:The short film
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373:Master Harmonic
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96:November 2011
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57: –
56:
52:
51:Find sources:
45:
41:
35:
34:
29:This article
27:
23:
18:
17:
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1310:
1303:Bibliography
1291:
1228:. Retrieved
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866:Persian Gulf
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807:Lake Ontario
799:Cabot Strait
793:area of the
774:Newfoundland
767:
759:World War II
756:
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619:tuberculosis
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491:Lane or Zone
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180:World War II
169:
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93:
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76:
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62:
50:
38:Please help
33:verification
30:
877:intervals.
870:Vietnam War
782:Quebec City
778:Nova Scotia
708:Beachy Head
692:Moray Firth
655:Isle of Man
533:longitude.
499:Purple lane
1408:Categories
1137:References
1065:Royal Navy
818:Vertol 107
700:Chichester
682:adoption.
542:Multipulse
537:Multipulse
515:Green lane
475:Decometers
258:hyperbolic
176:Royal Navy
142:hyperbolic
66:newspapers
1331:130079994
1142:Citations
874:Bad Iburg
849:VOR/DME.
679:Irish Sea
662:Irish Sea
624:U.S. Army
596:problem.
467:Admiralty
265:called a
193:North Sea
132:lattices.
1131:Datatrak
1105:See also
963:skywaves
946:HokkaidĹŤ
786:Montreal
653:and the
651:Anglesey
526:10563 m
518:586.8 m
510:440.1 m
507:Red lane
502:352.1 m
345:127.500
334:113.333
298:Harmonic
220:Overview
1230:17 June
1116:Loran-C
1032:VOR/DME
983:Bermuda
899:Brixham
770:Toronto
704:Swanage
675:Loran-C
613:Origins
600:History
581:Skywave
465:A 1967
364:Pattern
323:70.833
312:85.000
295:Station
267:pattern
204:Loran-C
178:during
80:scholar
1329:
1058:Hi-Fix
1041:Azores
1020:Dectra
1005:Dectra
990:Delrac
957:Delrac
716:Calais
384:Purple
317:Purple
306:Master
238:chains
140:was a
82:
75:
68:
61:
53:
1424:Decca
1327:S2CID
1317:(3).
907:Racal
903:Devon
483:zones
424:Green
339:Green
250:phase
184:D-Day
172:Decca
161:LORAN
87:JSTOR
73:books
1232:2022
1045:BOAC
1015:ICAO
998:POPI
919:ED50
706:and
628:Navy
626:and
447:lane
439:18f
419:24f
399:30f
159:and
136:The
59:news
1319:doi
996:'s
973:in
889:An
846:DME
842:VOR
643:Gee
593:GPS
404:Red
328:Red
209:GPS
157:Gee
153:kHz
42:by
1410::
1325:.
1315:44
1313:.
1274:^
1257:^
1240:^
1223:.
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1165:^
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915:ap
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891:ap
730:.
436:Ă—3
433:6f
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427:9f
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103:(
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84:·
77:·
70:·
63:·
36:.
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