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In 1968 Shirley Chisholm became the first Black woman elected to the United States Congress. In 1972 she launched a campaign for the Democratic presidential nomination, breaking another political barrier.
MORE →Reflects the personal views, recollections, and perspective of the author, Mike Davis.
This is a personal recollection on the Move fire on May 13, 1985
| Muang Phalan TACAN Site | |
|---|---|
| Site information | |
| Type | Air Force |
| Condition | abandoned |
| Location | |
 | |
| Coordinates | 16°39′29″N 105°33′40″E / 16.658°N 105.561°E |
| Site history | |
| Built | 1967 |
| In use | 1967 |
| Battles/wars |  Vietnam War |
| Garrison information | |
| Occupants | 1st Mobile Communications Group |
Muang Phalan TACAN Site (also known as Lima 61 Alternative or L-61A) was a U.S. Air Force facility built in the village of Muang Phalan, Laos, during the Vietnam War.
Muang Phalan TACAN Site was established by the U.S. Air Force in April 1967 as part of Operation Bright Light to create a network of TACAN sites to support air operations over southern Laos and Vietnam. The site operated as TACAN Channel 77.[1][2]
On 25 December 1967 the site was attacked by the People's Army of Vietnam who overran the facility killing the two "sheep-dipped" technicians from the 1st Mobile Communications Group.[1] A replacement TACAN site was installed at Mukdahan, Thailand.[2]
The site is abandoned and turned over to farmland and housing.
 | This article about the Vietnam War is a stub. You can help Wikipedia by adding missing information. |
Source: Wikipedia. Article content is retrieved live through the MediaWiki API.
Muang Phalan TACAN Site (also known as Lima 61 Alternative or L-61A) was a U.S. Air Force facility built in the village of Muang Phalan, Laos, during the Vietnam War.
A non-directional beacon (NDB) or non-directional radio beacon 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 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 the world's first instrument approach on May 9, 1932.
A very high frequency omnidirectional range station (VOR) is a type of short-range VHF radio navigation system for aircraft, enabling aircraft with a VOR receiver to determine the azimuth (also radial), referenced to magnetic north, between the aircraft to/from fixed VOR ground radio beacons. VOR and the first DME(1950) system (referenced to 1950 since different from today's DME/N) to provide the slant range distance, were developed in the United States as part of a U.S. civil/military program for Aeronautical Navigation Aids in 1945. Deployment of VOR and DME(1950) began in 1949 by the U.S. CAA (Civil Aeronautics Administration). ICAO standardized VOR and DME(1950) in 1950 in ICAO Annex, Edition 1. Frequencies for the use of VOR are standardized in the very high frequency (VHF) band between 108.00 and 117.95 MHz. To improve azimuth accuracy of VOR even under difficult siting conditions, Doppler VOR (DVOR) was developed in the 1960s. VOR is according to ICAO rules a primary means navigation system for commercial and general aviation, (D)VOR are gradually decommissioned and replaced by DME-DME RNAV (area navigation) 7.2.3 and satellite based navigation systems such as GPS in the early 21st century. In 2000 there were about 3,000 VOR stations operating around the world, including 1,033 in the US, but by 2013 the number in the US had been reduced to 967. The United States is decommissioning approximately half of its VOR stations and other legacy navigation aids as part of a move to performance-based navigation, while still retaining a "Minimum Operational Network" of VOR stations as a backup to GPS. In 2015, the UK started to reduce the number of stations from 44 to 19 which it completed in 2020. A VOR beacon radiates via two or more antennas an amplitude modulated signal and a frequency modulated subcarrier. By comparing the fixed 30 Hz reference signal with the rotating azimuth 30 Hz signal the azimuth from an aircraft to a (D)VOR is detected. The phase difference is indicative of the bearing from the (D)VOR station to the receiver relative to magnetic north. This line of position is called the VOR "radial". While providing the same signal over the air at the VOR receiver antennas. DVOR is based on the Doppler shift to modulate the azimuth dependent 30 Hz signal in space, by continuously switching the signal of about 25 antenna pairs that form a circle around the center 30 Hz reference antenna. The intersection of radials from two different VOR stations can be used to fix the position of the aircraft, as in earlier radio direction finding (RDF) systems. VOR stations are short range navigation aids limited to the radio-line-of-sight (RLOS) between transmitter and receiver in an aircraft. Depending on the site elevation of the VOR and altitude of the aircraft Designated Operational Coverages (DOC) of at max. about 200 nautical miles (370 kilometres) Att.C, Fig.C-13 can be achieved. The prerequisite is that the EIRP provides in spite of losses, e.g. due to propagation and antenna pattern lobing, for a sufficiently strong signal at the aircraft VOR antenna that it can be processed successfully by the VOR receiver. Each (D)VOR station broadcasts a VHF radio composite signal, including the mentioned navigation and reference signal, and a station's identifier and optional additional voice. 3.3.5 The station's identifier is typically a three-letter string in Morse code. While defined in Annex 10 voice channel is seldomly used today, e.g. for recorded advisories like ATIS. 3.3.6 A VORTAC is a radio-based navigational aid for aircraft pilots consisting of a co-located VHF omnidirectional range and a tactical air navigation system (TACAN) beacon. Both types of beacons provide pilots azimuth information, but the VOR system is generally used by civil aircraft and the TACAN system by military aircraft. However, the TACAN distance measuring equipment is also used for civil purposes because civil DME equipment is built to match the military DME specifications. Most VOR installations in the United States are VORTACs. The system was designed and developed by the Cardion Corporation. The Research, Development, Test, and Evaluation (RDT&E) contract was awarded 28 December 1981.
In aviation, distance measuring equipment (DME) is a radio navigation technology that measures the slant range (distance) between an aircraft and a ground station by timing the propagation delay of radio signals in the frequency band between 960 and 1215 megahertz (MHz). Line-of-sight between the aircraft and ground station is required. An interrogator (airborne) initiates an exchange by transmitting a pulse pair, on an assigned 'channel', to the transponder ground station. The channel assignment specifies the carrier frequency and the spacing between the pulses. After a known delay, the transponder replies by transmitting a pulse pair on a frequency that is offset from the interrogation frequency by 63 MHz and having specified separation. DME systems are used worldwide, using standards set by the International Civil Aviation Organization (ICAO), RTCA, the European Union Aviation Safety Agency (EASA) and other bodies. Some countries require that aircraft operating under instrument flight rules (IFR) be equipped with a DME interrogator; in others, a DME interrogator is only required for conducting certain operations. While stand-alone DME transponders are permitted, DME transponders are usually paired with an azimuth guidance system to provide aircraft with a two-dimensional navigation capability. A common combination is a DME co-located with a VHF omnidirectional range (VOR) transmitter in a single ground station, designated as VOR/DME. When this occurs, the frequencies of the VOR and DME equipment are paired. Such a configuration enables an aircraft to determine its azimuth angle and distance from the station, a rough 2D locationing capability. DME is compatible with the distance measuring component of TACAN, the military equivalent of VOR/DME with more accurate rangefinding. A VORTAC (VOR with TACAN) installation allows both military and civil aircraft access to 2D positioning. Low-power DME transponders are also associated with some instrument landing system (ILS), ILS localizer and microwave landing system (MLS) installations. In those situations, the DME transponder frequency/pulse spacing is also paired with the ILS, LOC or MLS frequency. ICAO characterizes DME transmissions as ultra high frequency (UHF). The term L-band is also used. DME is similar in principle to secondary radar ranging function, except the roles of the equipment in the aircraft and on the ground are reversed. DME was a post-war development based on the identification friend or foe (IFF) systems of World War II. Developed in Australia, DME was invented by James "Gerry" Gerrand. In 1945, after Edward George Bowen became Chief of the Division of Radiophysics at CSIRO, Brian Cooper developed DME. Based upon the Rebecca/Eureka transponding radar, the 200 MHz system weighed less, and used a dial instead of a screen. In 1946, the Provisional International Civil Aviation Organization adopted the VOR and DME airways model. In 1947, the system was deployed on commercial aircraft, and by 1953, all commercial aircraft in Australia were so equipped.
Before the 1921 destruction of Tulsa’s Greenwood District, Black residents had created a remarkable center of business and community life. The district included stores, professional offices, entertainment venues and homes owned by Black citizens. Understanding Greenwood means learning what was built—not only what was burned.
MORE →The Greenwood District.
