Selasa, 29 Desember 2009

Radio transceiver is a device that has both a transmitter and a receiver which are combined and share common circuitry or a single housing


A transceiver is a device that has both a transmitter and a receiver which are combined and share common circuitry or a single housing. If no circuitry is common between transmit and receive functions, the device is a transmitter-receiver. The term originated in the early 1920s. Technically, transceivers must combine a significant amount of the transmitter and receiver handling circuitry. Similar devices include transponders, transverters, and repeaters.

In radio terminology, a transceiver means a unit which contains both a receiver and a transmitter. It was quite common to have these units separated. Ham radio operators can build their own equipment and it is always easier to design and build a simple unit having one of the functions, transmitting or receiving. Almost every modern amateur radio equipment is now a transceiver but there is an active market for pure radio receivers, mainly for Shortwave listening operators. An example of a transceiver would be a walkie-talkie, or a CB radio.

A transmitter is an electronic device which, usually with the aid of an antenna, propagates an electromagnetic signal such as radio, television, or other telecommunications.

Generally in communication and information processing, a transmitter is any object (source) which sends information to an observer (receiver). When used in this more general sense, vocal chords may also be considered an example of a transmitter.

In radio electronics and broadcasting, a transmitter usually has a power supply, an oscillator, a modulator, and amplifiers for audio frequency (AF) and radio frequency (RF). The modulator is the device which piggybacks (or modulates) the signal information onto the carrier frequency, which is then broadcast. Sometimes a device (for example, a cell phone) contains both a transmitter and a radio receiver, with the combined unit referred to as a transceiver. In amateur radio, a transmitter can be a separate piece of electronic gear or a subset of a transceiver, and often referred to using an abbreviated form; "XMTR". In most parts of the world, use of transmitters is strictly controlled by laws since the potential for dangerous interference (for example to emergency communications) is considerable. In consumer electronics, a common device is a Personal FM transmitter, a very low power transmitter generally designed to take a simple audio source like an iPod, CD player, etc. and transmit it a few feet to a standard FM radio receiver. Most personal FM transmitters In the USA fall under Part 15 of the FCC regulations to avoid any user licensing requirements.

In industrial process control, a "transmitter" is any device which converts measurements from a sensor into a signal to be received, usually sent via wires, by some display or control device located a distance away. Typically in process control applications the "transmitter" will output an analog 4-20 mA current loop or digital protocol to represent a measured variable within a range. For example, a pressure transmitter might use 4 mA as a representation for 50 psig of pressure and 20 mA as 1000 psig of pressure and any value in between proportionately ranged between 50 and 1000 psig. (A 0-4 mA signal indicates a system error.) Older technology transmitters used pneumatic pressure typically ranged between 3 to 15 psig (20 to 100 kPa) to represent a process variable.

A radio receiver is an electronic circuit that receives its input from an antenna, uses electronic filters to separate a wanted radio signal from all other signals picked up by this antenna, amplifies it to a level suitable for further processing, and finally converts through demodulation and decoding the signal into a form usable for the consumer, such as sound, pictures, digital data, measurement values, navigational positions, etc.

Types of radio receivers

Various types of radio receivers may include:
  • Consumer audio and high fidelity audio receivers and AV receivers used by home stereo listeners and audio and home theatre system enthusiasts.
  • Communications receivers, used as a component of a radio communication link, characterized by high stability and reliability of performance.
  • Simple crystal radio receivers (also known as a crystal set) which operate using the power received from radio waves.
  • Satellite television receivers, used to receive television programming from communication satellites in geosynchronous orbit.
  • Specialized-use receivers such as telemetry receivers that allow the remote measurement and reporting of information.
  • Measuring receivers (also: measurement receivers) are calibrated laboratory-grade devices that are used to measure the signal strength of broadcasting stations, the electromagnetic interference radiation emitted by electrical products, as well as to calibrate RF attenuators and signal generators.
  • Scanners are specialized receivers that can automatically scan two or more discrete frequencies, stopping when they find a signal on one of them and then continuing to scan other frequencies when the initial transmission ceases. They are mainly used for monitoring VHF and UHF radio systems.
In telecommunication, the term transponder (short-for Transmitter-responder and sometimes abbreviated to XPDR, XPNDR, TPDR or TP) has the following meanings:
  • An automatic device that receives, amplifies, and retransmits a signal on a different frequency (see also broadcast translator).
  • An automatic device that transmits a predetermined message in response to a predefined received signal.
  • A receiver-transmitter that will generate a reply signal upon proper electronic interrogation.
A transverter is a radio frequency device that consists of an upconverter and a downconverter in one unit. Transverters are used in conjunction with transceivers to change the range of frequencies over which the transceiver can communicate.


Radio Data Transmitter - 868MHz
New wireless data transmitter for transferring large amounts of data wirelessly up to 300m. This compact easy to use unit connects directly to most microcontrollers with a standard SPI interface. FSK transmission with a PLL based tuner ensure reliable and accurate data transfer, with data transfer rates of up to 155K bps. Automatic antenna tuning and low power operation make this unit ideal for a wide range of applications.

Features
• Frequency - 868MHz
• FSK Transmission
• PLL Based
• Operating Voltage - 2.2 - 5.4 Vdc
• High Data Rate - Up to 115.2K bps
• Range - Up to 300m
• Works with most Microcontrollers, standard SPI Interface
• Dimensions: Length - 18mm, Width - 14mm , Height - 9mm (Including Pins)

A communications satellite’s channels are called transponders, because each is a separate transceiver or repeater. With digital video data compression and multiplexing, several video and audio channels may travel through a single transponder on a single wideband carrier. Original analog video only has one channel per transponder, with subcarriers for audio and automatic transmission identification service ATIS. Non-multiplexed radio stations can also travel in single channel per carrier (SCPC) mode, with multiple carriers (analog or digital) per transponder. This allows each station to transmit directly to the satellite, rather than paying for a whole transponder, or using landlines to send it to an earth station for multiplexing with other stations.

Remote Communications Outlets (RCO) are remote aviation band radio tranceivers, established to extend to communication capabilities of Flight Information Centres (FIC) and Flight Service Stations (FSS).

Pilots can find RCO frequencies in charts or publications such as the Airport/Facility Directory or Canada Flight Supplement. The RCO is used to make a radio call to the outlet as if the pilot were making the call directly to the FSS or FIC. The outlet will relay the call (and the briefer's response) automatically. RCOs are sometimes confused with RTRs, or remote transmitter/receivers. In fact, the difference between the two is subtle. While RCOs serve flight service stations, RTRs serve terminal air traffic control facilities.

RCOs and RTRs may be UHF or VHF and are divided into a variety of classes determined by the number of transmitters or receivers. Classes A through G are used mainly for air/ ground communications. Class O facilities were created specifically to provide ground-to-ground communication between air traffic controllers and pilots located at satellite airports. The idea was to create a way for pilots to receive en-route clearances or departure authorizations and cancel IFR flight plans. Class O RTRs also were intended to allow pilots flying below the coverage of the primary air/ground frequency to continue to receive advisories from air traffic control. Class O facilities are nonprotected outlets and are subject to prolonged outages which may go undetected and unreported.

Canada also uses a special variant called the Dial-up Remote Communications Outlet (DRCO). DRCOs connect to an FIC or FSS over a phone line, and pilots initiate the connection by keying their microphones in a prescribed pattern.

1 komentar:

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