In digital radio, packet radio is the application of packet switching techniques to digital radio communications. Packet radio uses a packet switching protocol as opposed to circuit switching or message switching protocols to transmit digital data via a radio communication link.
Radioteletype (RTTY) is a telecommunications system consisting originally of two or more electromechanical teleprinters in different locations connected by radio rather than a wired link. Radioteletype evolved from earlier landline teleprinter operations that began in the mid-1800s. The US Navy Department successfully tested printing telegraphy between an airplane and ground radio station in 1922. Later that year, the Radio Corporation of America successfully tested printing telegraphy via their Chatham, Massachusetts, radio station to the R.M.S. Majestic. Commercial RTTY systems were in active service between San Francisco and Honolulu as early as April 1932 and between San Francisco and New York City by 1934. The US military used radioteletype in the 1930s and expanded this usage during World War II. From the 1980s, teleprinters were replaced by personal computers (PCs) running software to emulate teleprinters.
An emergency position-indicating radiobeacon (EPIRB) is a type of emergency locator beacon for commercial and recreational boats, a portable, battery-powered radio transmitter used in emergencies to locate boaters in distress and in need of immediate rescue. In the event of an emergency, such as a ship sinking or medical emergency onboard, the transmitter is activated and begins transmitting a continuous 406 MHz distress radio signal, which is used by search-and-rescue teams to quickly locate the emergency and render aid. The signal is detected by satellites operated by an international consortium of rescue services, COSPAS-SARSAT, which can detect emergency beacons anywhere on Earth transmitting on the distress frequency of 406 MHz. The satellites calculate the position or utilize the GPS coordinates of the beacon and quickly passes the information to the appropriate local first responder organization, which performs the search and rescue. As Search and Rescue approach the search areas, they use Direction Finding (DF) equipment to locate the beacon using the 121.5 MHz homing signal, or in newer EPIRBs, the AIS location signal. The basic purpose of this system is to help rescuers find survivors within the so-called "golden day" during which the majority of survivors can usually be saved. The feature distinguishing a modern EPIRB, often called GPIRB, from other types of emergency beacon is that it contains a GPS receiver and broadcasts its position, usually accurate within 100 m (330 ft), to facilitate location. Previous emergency beacons without a GPS can only be localized to within 2 km (1.2 mi) by the COSPAS satellites and relied heavily upon the 121.5 MHz homing signal to pin-point the beacons location as they arrived on scene.
A communication channel refers either to a physical transmission medium such as a wire, or to a logical connection over a multiplexed medium such as a radio channel in telecommunications and computer networking. A channel is used for information transfer of, for example, a digital bit stream, from one or several senders to one or several receivers. A channel has a certain capacity for transmitting information, often measured by its bandwidth in Hz or its data rate in bits per second.
A pager, also known as a beeper or bleeper, is a wireless telecommunications device that receives and displays alphanumeric or voice messages. One-way pagers can only receive messages, while response pagers and two-way pagers can also acknowledge, reply to, and originate messages using an internal transmitter.
A subcarrier is a sideband of a radio frequency carrier wave, which is modulated to send additional information. Examples include the provision of colour in a black and white television system or the provision of stereo in a monophonic radio broadcast. There is no physical difference between a carrier and a subcarrier; the "sub" implies that it has been derived from a carrier, which has been amplitude modulated by a steady signal and has a constant frequency relation to it.
AX.25 is a data link layer protocol originally derived from layer 2 of the X.25 protocol suite and designed for use by amateur radio operators. It is used extensively on amateur packet radio networks.
A terminal node controller (TNC) is a device used by amateur radio operators to participate in AX.25 packet radio networks. It is similar in function to the Packet Assembler/Disassemblers used on X.25 networks, with the addition of a modem to convert baseband digital signals to audio tones.
The International Cospas-Sarsat Programme is a satellite-aided search and rescue (SAR) initiative. It is organized as a treaty-based, nonprofit, intergovernmental, humanitarian cooperative of 45 nations and agencies. It is dedicated to detecting and locating emergency locator radio beacons activated by persons, aircraft or vessels in distress, and forwarding this alert information to authorities that can take action for rescue. Member countries support the distribution of distress alerts using a constellation of around 65 satellites orbiting the Earth which carry transponders and signal processors capable of locating an emergency beacon anywhere on Earth transmitting on the Cospas-Sarsat frequency of 406 MHz.
An amateur radio repeater is an electronic device that receives a weak or low-level amateur radio signal and retransmits it at a higher level or higher power, so that the signal can cover longer distances without degradation. Many repeaters are located on hilltops or on tall buildings as the higher location increases their coverage area, sometimes referred to as the radio horizon, or "footprint". Amateur radio repeaters are similar in concept to those used by public safety entities, businesses, government, military, and more. Amateur radio repeaters may even use commercially packaged repeater systems that have been adjusted to operate within amateur radio frequency bands, but more often amateur repeaters are assembled from receivers, transmitters, controllers, power supplies, antennas, and other components, from various sources.
Winlink, or formally, Winlink Global Radio Email, also known as the Winlink 2000 Network, is a worldwide radio messaging system that uses amateur-band radio frequencies and government frequencies to provide radio interconnection services that include email with attachments, position reporting, weather bulletins, emergency and relief communications, and message relay. The system is built and administered by volunteers and is financially supported by the Amateur Radio Safety Foundation.
In navigation, a radio beacon or radiobeacon is a kind of beacon, a device that marks a fixed location and allows direction-finding equipment to find relative bearing. But instead of employing visible light, radio beacons transmit electromagnetic radiation in the radio wave band. They are used for direction-finding systems on ships, aircraft and vehicles.
The Citizen Weather Observer Program (CWOP) is a network of privately owned electronic weather stations concentrated in the United States but also located in over 150 countries. Network participation allows volunteers with computerized weather stations to send automated surface weather observations to the National Weather Service (NWS) by way of the Meteorological Assimilation Data Ingest System (MADIS). This data is then used by the Rapid Refresh (RAP) and other forecast models to produce forecasts. Observations are also redistributed to the public.
Radio is the technology of communicating using radio waves. Radio waves are electromagnetic waves of frequency between 3 hertz (Hz) and 300 gigahertz (GHz). They are generated by an electronic device called a transmitter connected to an antenna which radiates oscillating electrical energy, often characterized as a wave. They can be received by other antennas connected to a radio receiver, this is the fundamental principle of radio communication. In addition to communication, radio is used for radar, radio navigation, remote control, remote sensing, and other applications.
Formation Autonomy Spacecraft with Thrust, Relnav, Attitude and Crosslink is a pair of nanosatellites developed and built by students at The University of Texas at Austin. The project is part of a program sponsored by the Air Force Research Laboratory (AFRL), whose goal is to lead the development of affordable space technology. The FASTRAC mission will specifically investigate technologies that facilitate the operation of multiple satellites in formation. These enabling technologies include relative navigation, cross-link communications, attitude determination, and thrust. Due to the high cost of lifting mass into orbit, there is a strong initiative to miniaturize the overall weight of spacecraft. The utilization of formations of satellites, in place of large single satellites, reduces the risk of single point failure and allows for the use of low-cost hardware.
Automatic Dependent Surveillance–Broadcast (ADS-B) is an aviation surveillance technology and form of electronic conspicuity in which an aircraft determines its position via satellite navigation or other sensors and periodically broadcasts its position and other related data, enabling it to be tracked. The information can be received by air traffic control ground-based or satellite-based receivers as a replacement for secondary surveillance radar (SSR). Unlike SSR, ADS-B does not require an interrogation signal from the ground or from other aircraft to activate its transmissions. ADS-B can also receive point-to-point by other nearby equipped ADS-B equipped aircraft to provide traffic situational awareness and support self-separation.
AMSAT-OSCAR 16, also known as AO-16 and PACSAT, is the in-orbit name designation of an amateur radio satellite of the OSCAR series. It was built by AMSAT and was launched on 22 January 1990 from Kourou, French Guiana on an Ariane 4 launch vehicle. It is in Sun synchronous low Earth orbit.
An amateur radio satellite is an artificial satellite built and used by amateur radio operators. It forms part of the Amateur-satellite service. These satellites use amateur radio frequency allocations to facilitate communication between amateur radio stations.
APRS Calling is a manual procedure for calling stations on the Automatic Packet Reporting System (APRS) to initiate communications on another frequency, or possibly by other means. It is inspired by Digital Selective Calling, a part of the Global Maritime Distress Safety System. It also builds on existing digital procedures inherited from morse code and radioteletype operation. ITU Q codes are used in conjunction with APRS text messages to implement APRS calling. APRS calling is intended to complement monitoring voice calling frequencies.
An emergency locator beacon is a radio beacon, a portable battery powered radio transmitter, used to locate airplanes, vessels, and persons in distress and in need of immediate rescue. Various types of emergency locator beacons are carried by aircraft, ships, vehicles, hikers and cross-country skiers. In case of an emergency, such as the aircraft crashing, the ship sinking, or a hiker becoming lost, the transmitter is deployed and begins to transmit a continuous radio signal, which is used by search and rescue teams to quickly find the emergency and render aid. The purpose of all emergency locator beacons is to help rescuers find survivors within the so-called "golden day", the first 24 hours following a traumatic event, during which the majority of survivors can usually be saved.
