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47-815: The two spacecraft used for the ANDE mission are the Mock ANDE Active (MAA) sphere (Navy- OSCAR 61) and the Fence Calibration (FCAL) sphere (OSCAR 62). These microsatellites, developed by the Naval Research Laboratory , will measure drag through the use of precision orbit determination. Ground-based lasers will be used to track the orbits of the sphere to with a couple centimeters of accuracy. Perturbations caused by density gradients and winds will be backed out from these measurements. The two ANDE satellites are nearly perfect spheres; this

94-412: A communication channel , it is progressively degraded due to loss of power. For example, when a telephone call passes through a wire telephone line , some of the power in the electric current which represents the audio signal is dissipated as heat in the resistance of the copper wire. The longer the wire, the more power is lost, and the smaller the amplitude of the signal at the far end. So with

141-575: A linear transponder for two-way communications in real time. Some satellites have a bulletin board for store-and-forward digital communications, or a digipeater for direct packet radio connections. Amateur satellites have been launched into low Earth orbits and into highly elliptical orbits . Currently, amateur satellites support many different types of operation, including FM voice and SSB voice, as well as digital communications of AX.25 FSK ( Packet radio ) and PSK-31 . Uplink and downlink designations use sets of paired letters following

188-410: A telephone repeater is an amplifier in a telephone line , an optical repeater is an optoelectronic circuit that amplifies the light beam in an optical fiber cable ; and a radio repeater is a radio receiver and transmitter that retransmits a radio signal. A broadcast relay station is a repeater used in broadcast radio and television . When an information-bearing signal passes through

235-424: A DC current source to increase the power of the alternating current audio signal on the line. Since the telephone is a duplex (bidirectional) communication system, the wire pair carries two audio signals , one going in each direction. So telephone repeaters have to be bilateral, amplifying the signal in both directions without causing feedback, which complicates their design considerably. Telephone repeaters were

282-421: A city, or neighboring police departments). They may provide links to the public switched telephone network as well, or satellite network ( BGAN , INMARSAT , MSAT ) as an alternative path from source to the destination. Typically a repeater station listens on one frequency, A, and transmits on a second, B. All mobile stations listen for signals on channel B and transmit on channel A. The difference between

329-422: A linear amplifier, and may include electronic filters to compensate for frequency and phase distortion in the line. The digital repeater is used in channels that transmit data by binary digital signals , in which the data is in the form of pulses with only two possible values, representing the binary digits 1 and 0. A digital repeater amplifies the signal, and it also may retime, resynchronize, and reshape

376-403: A long enough wire the call will not be audible at the other end. Similarly, the greater the distance between a radio station and a receiver , the weaker the radio signal , and the poorer the reception. A repeater is an electronic device in a communication channel that increases the power of a signal and retransmits it, allowing it to travel further. Since it amplifies the signal, it requires

423-495: A predictable level of reliable communication over the designed coverage area. Repeaters can be divided into two types depending on the type of data they handle: This type is used in channels that transmit data in the form of an analog signal in which the voltage or current is proportional to the amplitude of the signal, as in an audio signal. They are also used in trunklines that transmit multiple signals using frequency division multiplexing (FDM). Analog repeaters are composed of

470-436: A source of electric power . The term "repeater" originated with telegraphy in the 19th century, and referred to an electromechanical device (a relay ) used to regenerate telegraph signals. Use of the term has continued in telephony and data communications . In computer networking , because repeaters work with the actual physical signal, and do not attempt to interpret the data being transmitted, they operate on

517-728: A stainless steel substrate which is used for coarse sun sensing and is another technology demonstrator. The FCAL sphere uses standard photodiodes. ANDE was deployed from the Space Shuttle Discovery on December 21, 2006 near the end of the STS-116 ISS servicing mission. The ANDE-FCAL satellite deployed and is functioning, however the ANDE-MAA failed to deploy at the same time as the FCAL sphere after it became stuck in its launch canister. The deployment of these spheres

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564-414: A wire line or a radio link. While the repeater station is designed for simultaneous reception and transmission, mobile units need not be equipped with the bulky and costly duplexers, as they only transmit or receive at any time. Mobile units in a repeater system may be provided with a "talkaround" channel that allows direct mobile-to-mobile operation on a single channel. This may be used if out of reach of

611-550: Is a list of major amateur satellites in Japanese Misplaced Pages ). Es’hail 2 / QO-100 Launched November 15, 2018.In geostationary orbit covering Brazil to Thailand. Narrowband Linear transponder 2400.050 - 2400.300 MHz Uplink 10489.550 - 10489.800 MHz Downlink Wideband digital transponder 2401.500 - 2409.500 MHz Uplink 10491.000 - 10499.000 MHz Downlink The first amateur satellites contained telemetry beacons. Since 1965, most OSCARs carry

658-403: Is amplified and retransmitted, often on another frequency, to provide coverage beyond the obstruction. Usage of a duplexer can allow the repeater to use one antenna for both receive and transmit at the same time. Radio repeaters improve communication coverage in systems using frequencies that typically have line-of-sight propagation . Without a repeater, these systems are limited in range by

705-670: Is possible, but it is difficult to remain precisely near the frequency. Frequency modulation is more tolerant of doppler shifts than single-sideband , and therefore FM is much easier to tune manually. A number of low Earth orbit (LEO) OSCAR satellites use frequency modulation (FM). These are also commonly referred to as "FM LEOs" or the "FM Birds". Such satellites act as FM amateur radio repeaters that can be communicated through using commonly available amateur radio equipment. Communication can be achieved with handheld transceivers using manual doppler correction. Satellite passes are typically less than 15 minutes long. The names of

752-451: Is published by AMSAT . AMSAT has not been actively involved in the launch and operation of most amateur satellites in the last two decades beyond allocating an OSCAR number. The first amateur satellite, simply named OSCAR 1, was launched on December 12, 1961, barely four years after the launch of the world's first satellite, Sputnik I . The satellite had to be built in a very specific shape and weight, so it could be used in place of one of

799-465: The physical layer , the first layer of the OSI model ; a multiport Ethernet repeater is usually called a hub . This is used to increase the range of telephone signals in a telephone line. They are most frequently used in trunklines that carry long distance calls. In an analog telephone line consisting of a pair of wires, it consists of an amplifier circuit made of transistors which use power from

846-450: The satellite . The satellite in turn, will be receiving the uplink signal at a higher frequency than normal so the ground station's transmitted uplink frequency must be lower to be received by the satellite. After the satellite passes overhead and begins to move away, this process is reversed. The downlink frequency will appear lower and the uplink frequency will need to be adjusted higher . The following mathematical formulas relate

893-569: The 435-438 MHz band is particularly popular for amateur/educational small satellites such as Cubesats. Repeater In telecommunications , a repeater is an electronic device that receives a signal and retransmits it. Repeaters are used to extend transmissions so that the signal can cover longer distances or be received on the other side of an obstruction. Some types of repeaters broadcast an identical signal, but alter its method of transmission, for example, on another frequency or baud rate . There are several different types of repeaters;

940-487: The Amateur-satellite service. These satellites use amateur radio frequency allocations to facilitate communication between amateur radio stations. Many amateur satellites receive an OSCAR designation, which is an acronym for Orbiting Satellite Carrying Amateur Radio . The designation is assigned by AMSAT , an organization which promotes the development and launch of amateur radio satellites. Because of

987-472: The Doppler shift to the velocity of the satellite. Due to the complexity of finding the relative velocity of the satellite and the speed with which these corrections must be made, these calculations are normally accomplished using satellite tracking software . Many modern transceivers include a computer interface that allows for automatic doppler effect correction . Manual frequency-shift correction

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1034-511: The E6 repeater was the final major type used in the Bell System before the low cost of digital transmission made all voiceband repeaters obsolete. Frequency frogging repeaters were commonplace in frequency-division multiplexing systems from the middle to late 20th century. This is a type of telephone repeater used in underwater submarine telecommunications cables . This is used to increase

1081-478: The Earth's atmosphere (or never successfully left it). The country listing denotes the country that constructed the satellite and not the launching country. Currently, 30 countries have launched an OSCAR satellite. These countries, in chronological order by date of launch, include: SuitSat , an obsolete Russian space suit with a transmitter aboard, was officially known as "AMSAT-OSCAR 54". Coincidentally, "Oscar"

1128-513: The airplane-based tests. Once it was found to be operative and reliable, the satellite was shipped to Kennedy Space Center, where it was mounted in the launch vehicle's third stage . OSCAR 10's dimensions were: Height: 1.35 m (53 in) Width: 2.0 m (78.75 in) Weight: 140 kg at launch; 90 kg post engine firings. Other programs besides OSCAR have included Iskra (Soviet Union) circa 1982, JAS-1 (Fuji-OSCAR 12) (Japan) in 1986, RS (Soviet Union and Russia), and CubeSats . (There

1175-472: The components for OSCAR 10 were "off the shelf". Jan King led the project. Solar cells were bought in batches of 10 or 20 from Radio Shack , and tested for efficiency by group members. The most efficient cells were kept for the project; the rest were returned to RadioShack. Once ready, OSCAR 10 was mounted aboard a private plane, and flown a couple of times to evaluate its performance and reliability. Special QSL cards were issued to those who participated in

1222-415: The curvature of the Earth and the blocking effect of terrain or high buildings. A repeater on a hilltop or tall building can allow stations that are out of each other's line-of-sight range to communicate reliably. Radio repeaters may also allow translation from one set of radio frequencies to another, for example to allow two different public service agencies to interoperate (say, police and fire services of

1269-431: The first type of repeater and were some of the first applications of amplification. The development of telephone repeaters between 1900 and 1915 made long-distance phone service possible. Now, most telecommunications cables are fiber-optic cables which use optical repeaters (below). Before the invention of electronic amplifiers, mechanically coupled carbon microphones were used as amplifiers in telephone repeaters. After

1316-471: The high orbital speed of the amateur satellites, the uplink and downlink frequencies will vary during the course of a satellite pass . This phenomenon is known as the Doppler effect . While the satellite is moving towards the ground station, the downlink frequency will appear to be higher than normal. Hence, the receiver frequency at the ground station must be adjusted higher to continue receiving

1363-460: The launch vehicle ballast weights. OSCAR 1 was the first satellite to be ejected as a secondary payload (the primary payload was Discoverer 36 ) and to subsequently enter a separate orbit. It carried no on-board propulsion and its orbit decayed quickly. Despite orbiting for only 22 days, OSCAR 1 was an immediate success and led to follow-on missions. Over 570 amateur radio operators in 28 countries forwarded observations to Project OSCAR. Most of

1410-460: The majority of service-allocations stipulated in this document were incorporated in national Tables of Frequency Allocations and Utilisations which is within the responsibility of the appropriate national administration. The allocation might be primary, secondary, exclusive, and shared. In addition to the formal allocations in the main table such as above, there is also a key ITU-R footnote RR 5.282 that provides for additional allocations:- Of these,

1457-454: The power of the signal, an electronic filter which reshapes the pulses, and a laser which converts the electrical signal to light again and sends it out the other fiber. However, optical amplifiers are being developed for repeaters to amplify the light itself without the need of converting it to an electric signal first. This is used to extend the range of coverage of a radio signal. The history of radio relay repeaters began in 1898 from

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1504-495: The prevalence of this designation, amateur radio satellites are often referred to as OSCARs. These satellites can be used free of charge by licensed amateur radio operators for voice ( FM , SSB ) and data ( AX.25 , packet radio , APRS ) communications. Currently, over 18 fully operational amateur radio satellites are in orbit. They may be designed to act as repeaters , as linear transponders , and as store and forward digital relays. Amateur radio satellites have helped advance

1551-493: The publication by Johann Mattausch in Austrian Journal Zeitschrift für Electrotechnik (v. 16, 35 - 36). But his proposal "Translator" was primitive and not suitable for use. The first relay system with radio repeaters, which really functioned, was that invented in 1899 by Emile Guarini-Foresio. A radio repeater usually consists of a radio receiver connected to a radio transmitter. The received signal

1598-401: The range of signals in a fiber-optic cable . Digital information travels through a fiber-optic cable in the form of short pulses of light. The light is made up of particles called photons , which can be absorbed or scattered in the fiber. An optical communications repeater usually consists of a phototransistor which converts the light pulses to an electrical signal, an amplifier to increase

1645-413: The repeater system, or for communications not requiring the attention of all mobiles. The "talkaround" channel may be the repeater output frequency; the repeater will not retransmit any signals on its output frequency. An engineered radio communication system designer will analyze the coverage area desired and select repeater locations, elevations, antennas, operating frequencies and power levels to permit

1692-473: The same purposes as those of the amateur service .» This radiocommunication service is classified in accordance with ITU Radio Regulations (article 1) as follows: Radiocommunication service (article 1.19) The allocation of radio frequencies is provided according to Article 5 of the ITU Radio Regulations (edition 2012). In order to improve harmonisation in spectrum utilisation,

1739-487: The satellite should be based on computed models of the space environment. Beside their use in the in-situ determination of upper atmospheric density these satellites also function as technology demonstrators and as amateur radio digipeaters . Each satellite can be accessed via amateur radio using the APRS protocol. Part of the technology demonstration was the integration of a command and telemetry system that would not require

1786-416: The satellites below are sorted in chronological order by launch date, ascending. The status column denotes the current operational status of the satellite. Green signifies that the satellite is currently operational, orange indicates that the satellite is partially operational or failing. Red indicates that the satellite is non operational and black indicates that the satellite has re-entered

1833-475: The science of satellite communications. Contributions include the launch of the first satellite voice transponder (OSCAR 3) and the development of highly advanced digital "store-and-forward" messaging transponder techniques. The Amateur Radio Satellite community is very active in building satellites and in finding launch opportunities. Lists of functioning satellites need updating regularly, as new satellites are launched and older ones fail. Current information

1880-508: The sphere as round and smooth as possible. The ANDE MAA sphere is made from a proprietary alloy of AL 6061 that is castable, while the FCAL sphere is made from brass. The ANDE FCAL sphere has the distinction of being the only micro satellite to have its structure composed primarily of brass. The differences in materials and hence density and mass of the spheres will cause them to separate from each other along track over time. This separation will be measured and compared to predicted models of where

1927-496: The structure X/Y where X is the uplink band and Y is the downlink band. Occasionally, the downlink letter is rendered in lower case (i.e., X/y ). With a few exceptions, the letters correspond to IEEE's standard for radar frequency letter bands... Prior to the launch of OSCAR 40, operating modes were designated using single letters to indicate both uplink and downlink bands. While deprecated, these older mode designations are still widely used in casual conversation. Due to

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1974-432: The turn of the 20th century it was found that negative resistance mercury lamps could amplify, and they were used. The invention of audion tube repeaters around 1916 made transcontinental telephony practical. In the 1930s vacuum tube repeaters using hybrid coils became commonplace, allowing the use of thinner wires. In the 1950s negative impedance gain devices were more popular, and a transistorized version called

2021-415: The two frequencies may be relatively small compared to the frequency of operation, say 1%. Often the repeater station will use the same antenna for transmission and reception; highly selective filters called "duplexers" separate the faint incoming received signal from the billions of times more powerful outbound transmitted signal. Sometimes separate transmitting and receiving locations are used, connected by

2068-539: The use of normal antennas that would destroy the spherical shape of the micro satellites. The MAA sphere communicates by electrically isolating its two hemispheres with an insulating center disk. The FCAL sphere actually does deploy four whip antennas but each antenna is only a few thousandths of an inch in diameter. Power is provided to these microsatellites using lithium inorganic primary cells – another technology demonstrator. The MAA also has photovoltaic cells made from copper indium gallium selenide (CIGS) deposited on

2115-429: Was another technology demonstrator for the newly developed Canister for All Payload Ejections (CAPE) system. One of the difficulties encountered and solved with this technology was the ability to restrain and deploy microsatellites that did not have any type of standard attachment points. OSCAR An amateur radio satellite is an artificial satellite built and used by amateur radio operators . It forms part of

2162-424: Was done to make the drag on the satellites independent of their orientation, and because the drag coefficient, optical cross-sections, and radar cross sections of spheres are well understood. Each spherical micro satellite was constructed using the novel technique of centrifugal casting . This manufacturing technique was advantageous due to its low cost and its ability to achieve the high tolerances necessary to make

2209-635: Was the name given to an obsolete space suit by its young owner in the 1958 novel Have Space Suit—Will Travel , by Robert A. Heinlein . This book was first published a year after the launch of Sputnik 1 , the world's first artificial satellite. Amateur-satellite service (also: amateur-satellite radiocommunication service ) is – according to Article 1.57 of the International Telecommunication Union's (ITU) Radio Regulations (RR) – defined as « A radiocommunication service using space stations on earth satellites for

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