Milestone-Proposal:LORAN: Difference between revisions
From ETHW
(Article updated via HTTP request) |
(Article updated via HTTP request) |
||
| Line 1: | Line 1: | ||
{{ProposalEdit|a1=LORAN|a2a=Cambridge MA|a2b=Boston Section|a3=1940 to 1946|a4= | {{ProposalEdit|a1=LORAN|a2a=Cambridge MA|a2b=Boston Section|a3=1940 to 1946|a4=WHAT IS LORAN? Loran is a hyperbolic system of navigation by which difference in distance from two points on shore is determined by measurement of the time interval between reception of pulse- modulated synchronized signals from transmitters at the two points. Both ground waves and sky waves can be used to provide coverage over an extensive area with few stations, depending on design frequencies. An important advantage of loran at the time of its development during WW2, was that a ship could use loran without breaking radio silence. Loran transmitting stations work in pairs. Synchronization is achieved by letting the signals of the master station, control those of the slave station. To help overcome the disadvantage of requiring two transmitting stations for a single family of hyperbolic lines of positions, loran forms a chain of stations, so that each station except the end ones operate with the station on either side to form an intersecting lattice of position lines. To find their way, loran navigators must have an radio receiver-indicator, a time piece, and a set of loran nautical charts or loran tables. Standard loran was initially developed primarily for navigation over water. It was also used for air-borne navigation. | ||
DESCRIPTION | |||
Loran consist of three components: 1. a chain of radio transmitters creating an electronic lattice or grid upon the surface of the earth. 2. a loran receiver-indicator, something like an electronic timer with a cathode ray tube and 3. loran nautical and aeronautical charts or tables published, for example, by the US Navy Hydrographic Office. | Loran consist of three components: 1. a chain of radio transmitters creating an electronic lattice or grid upon the surface of the earth. 2. a loran receiver-indicator, something like an electronic timer with a cathode ray tube and 3. loran nautical and aeronautical charts or tables published, for example, by the US Navy Hydrographic Office. | ||
A simple explanation of how a navigator used loran in the 1940s to determine his position or fix follows next: first the line of position was established by measuring the relative time of arrival of two pulses which were known to have left two separate transmitters at times differing by a known interval. The time difference was noted in microseconds. With this information, charts and compasses, the navigator could plot a series of points on a chart plotting a line of position. But hold on; no fix point yet. A loran network with only two stations cannot provide meaningful navigation information as the 2-dimensional position of the receiver cannot be fixed without additional information to find the fix position. He may use a second pair of loran stations to determine a new line of position. Crossing of these two lines of position is the loran fix. For those wanting more details on hyperbolic system of navigation, see Chapter X111 of Bowditch's American Practical Navigator. | A simple explanation of how a navigator used loran in the 1940s to determine his position or fix follows next: first the line of position was established by measuring the relative time of arrival of two pulses which were known to have left two separate transmitters at times differing by a known interval. The time difference was noted in microseconds. With this information, charts and compasses, the navigator could plot a series of points on a chart plotting a line of position. But hold on; no fix point yet. A loran network with only two stations cannot provide meaningful navigation information as the 2-dimensional position of the receiver cannot be fixed without additional information to find the fix position. He may use a second pair of loran stations to determine a new line of position. Crossing of these two lines of position is the loran fix. For those wanting more details on hyperbolic system of navigation, see Chapter X111 of Bowditch's American Practical Navigator. | ||
Today's loran operates on one of several frequencies between1700 and 2000 kHz. It enjoys propagation characteristics determined primarily by soil conductivity and ionospheric conditions. Both ground wave and sky waves can be used to provide coverage over an extensive area with few stations. Usually. stations of a pairs are located 200 to 400 miles or more. At one time, several station pairs were separated by 1000 to 1400 miles apart. Transmitters now in use radiate about 100kw and give a ground-wave range oversea water of about 700 nautical miles in the daytime. The day time range over land is seldom more than 250 miles even for high-flying aircraft and is scarcely 100miles at the surface of the earth. At night the ground-wave range oversea water is reduced to about 500 miles by the increase in atmospheric noise, but sky waves, which are almost completely absorbed by day,become effective and increase the reliable night range to about 1400miles. Generally,, a number of stations are located so as to form a chain, with all but the end station in the group being double pulsing. In most parts of the world,, signaals can be received from at least two pairs of stations making it possible to determine a fix using loran alone. | Today's loran operates on one of several frequencies between1700 and 2000 kHz. It enjoys propagation characteristics determined primarily by soil conductivity and ionospheric conditions. Both ground wave and sky waves can be used to provide coverage over an extensive area with few stations. Usually. stations of a pairs are located 200 to 400 miles or more. At one time, several station pairs were separated by 1000 to 1400 miles apart. Transmitters now in use radiate about 100kw and give a ground-wave range oversea water of about 700 nautical miles in the daytime. The day time range over land is seldom more than 250 miles even for high-flying aircraft and is scarcely 100miles at the surface of the earth. At night the ground-wave range oversea water is reduced to about 500 miles by the increase in atmospheric noise, but sky waves, which are almost completely absorbed by day,become effective and increase the reliable night range to about 1400miles. Generally,, a number of stations are located so as to form a chain, with all but the end station in the group being double pulsing. In most parts of the world,, signaals can be received from at least two pairs of stations making it possible to determine a fix using loran alone. | ||
A BRIEF HISTORY | |||
The name loran is derived from long-range navigation, a name given by Lawrence M. Harding, a career officer of the United States Coast Guard (USGC). Harding is one of the loran pioneers not to be forgotten. USCG played a key role in getting loran transmitter stations up and running in the Aleutian Islands in 1943. USGC has been manning loran stations in this part of the world ever since. But other individuals should be mentioned: | |||
1941 - Melville Eastman of the Microwave Committee: first leader of the Rad Lab group or division assigned to develop radio navigation. In the spring of 1941, a small the founder of General Radio Corporation of Cambridge, was organized under the newly formed Radiation Laboratory of the Massachusetts Institute of Technology, from which it drew two or three key personnel, while other were recruited from outside sources. Further research and investigations were undertaken and soon indicated that changes in the basic design were necessary.. | |||
radio frequency, patterns, wave reflection | |||
When a grande long-lived engineered system like LORAN, .. this nomination milestone gives credit to those persons that worked on the so-called Project 3 or C | |||
. The USCG had a permanent office working on this project. One person in particular that deserves mention is Coast Guard Lt. Cmdr. L.M. Harding who provided supervision and direction for the Pacific Loran ... | . The USCG had a permanent office working on this project. One person in particular that deserves mention is Coast Guard Lt. Cmdr. L.M. Harding who provided supervision and direction for the Pacific Loran ... | ||
n, . . He was replaced by Jack Pierce of Harvard .. was an authority | |||
Long lasting near global radio navigation system. Evolved from LORAN, SS-LORAN, LORAN-A, and LORAN-C which was taken out of service recently. | Long lasting near global radio navigation system. Evolved from LORAN, SS-LORAN, LORAN-A, and LORAN-C which was taken out of service recently. | ||
Period of interests: 1940 to 1946 when a new from of radio navigation is proposed, 1941 when R&D work begins, throughout WW2, to 1946 when LORAN is a well established engineered system globally. LORAN's service to just recently is treayed in ..... . | Period of interests: 1940 to 1946 when a new from of radio navigation is proposed, 1941 when R&D work begins, throughout WW2, to 1946 when LORAN is a well established engineered system globally. LORAN's service to just recently is treayed in ..... . | ||
| Line 26: | Line 24: | ||
Among his many awards are a 1948 Presidential Certificate of Merit and the 1953 Morris Liebmann Prize of the Institute of Radio Engineers. | Among his many awards are a 1948 Presidential Certificate of Merit and the 1953 Morris Liebmann Prize of the Institute of Radio Engineers. | ||
JA Pierce was . . .???///// | JA Pierce was . . .???///// | ||
LORAN CITATION | LORAN CITATION | ||
JA Pierce | JA Pierce | ||
Revision as of 20:16, 10 December 2010
This Proposal has not been submitted and may only be edited by the original author.
Pierce Loran.pdf
Loran1.jpg .png
Loran_chart.png
This is a test
