Description
A transmitter can be a separate piece of electronic equipment, or an electrical circuit within another electronic device. A transmitter and receiver combined in one unit is called a transceiver. The term transmitter is often abbreviated "XMTR" or "TX" in technical documents. The purpose of most transmitters is radio communication of information over a distance. The information is provided to the transmitter in the form of an electronic signal, such as an audio (sound) signal from a microphone, a video (TV) signal from a video camera, or in wireless networking devices a digital signal from a computer. The transmitter combines the information signal to be carried with the radio frequency signal which generates the radio waves, which is often called the carrier. This process is called modulation. The information can be added to the carrier in several different ways, in different types of transmitter. In an amplitude modulation (AM) transmitter, the information is added to the radio signal by varying its amplitude. In a frequency modulation (FM) transmitter, it is added by varying the radio signal's frequency slightly. Many other types of modulation are used.
The antenna may be enclosed inside the case or attached to the outside of the transmitter, as in portable devices such as cell phones, walkie-talkies, and garage door openers. In more powerful transmitters, the antenna may be located on top of a building or on a separate tower, and connected to the transmitter by a feed line, that is a transmission line.
Modern amateur radio transceiver, the ICOM IC-746PRO. It can transmit on the amateur bands from 1.8 MHz to 144 MHz with an output power of 100 W. A CB radio transceiver, a two way radio transmitting on 27 MHz with a power of 4 watts, that can be operated without a license Emergency Locator Beacon transmitter carried on ships. If the ship sinks, the beacon broadcasts a distress radio signal on 406 MHz which is picked up by a Search and Rescue satellite to find the ship. A garage door opener control contains a low-power 2.4 GHz transmitter that sends coded commands to the garage door mechanism to open or close. An RFID chip (next to rice grain) contains a tiny transmitter that transmits an identification number. They are incorporated into consumer products, and even implanted in pets. In a wireless computer network, wireless routers like this contain a 2.4 GHz transmitter that sends downloaded web pages and email to local computers.Read more about this topic: Transmitter
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