Archive for the ‘Outdoor Transmitters’ Category

Outdoor Transmitters

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. In other applications signals can also be transmitted using an analog 0/4-20 mA current loop signal.

Transmitter types
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. A common consumer electronics 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. In the USA, most personal FM transmitters fall under Part 15 of the FCC regulations to avoid any user licensing requirements.

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 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.

Generally and 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 cords may also be considered an example of a transmitter.

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