Mobile radio Anirudh Nanda RC6703B48, 3060070098 B.Tech-M.Tech(ECE) Lovely Professional University Abstract:- off of 72- or 30-volt DC power. A large ship with 117V AC power might have a base station mounted on the ship's bridge. The term paper includes a brief introduction to mobile radio communication. This term paper also includes a brief mention 2.Disambiguation: Two-way versus telephone of 2 way comm’n,it’s history, the role that it plays in our everyday life with its various future advancements. It also The distinction between radiotelephones and two-way radio is includes a discussion of antennas , Multiple controls, becoming blurred as the two technologies merge. The microphones,data radio, Walkie talkie converters and it’s main backbone or infrastructure supporting the system defines application Professional Mobile Radio with a feature of which category or taxonomy applies. A parallel to this concept selective calling. is the convergence of computing and telephones. 1. Introduction Radiotelephones are full-duplex (simultaneous talk and listen), circuit switched, and primarily communicate with Mobile radio or mobiles refer to wireless communications telephones connected to the public switched telephone systems and devices which are based on radio frequencies, network. The connection sets up based on the user dialing. and where the path of communications is movable on either The connection is taken down when the end button is pressed. end. There are a variety of views about what constitutes They run on telephony-based infrastructure such as AMPS or mobile equipment. For US licensing purposes, mobiles may GSM. include hand-carried, (sometimes called portable), equipment. An obsolete term is radiophone. Two-way radio is primarily a dispatch tool intended to communicate in simplex or half-duplex modes using push-to- Some mobile radios are mounted in aircraft, (aeronautical talk, and primarily intended to communicate with other radios mobile), shipboard, (maritime mobile), on motorcycles, or rather than telephones. These systems run on push-to-talk- railroad locomotives. Power may vary with each platform. For based infrastructure such as Nextel's iDEN, Specialized example, a mobile radio installed in a locomotive would run Mobile Radio (SMR), MPT-1327, Enhanced Specialized Mobile Radio (ESMR) or conventional two-way systems. Certain modern two-way radio systems may have full-duplex To transmit a message, the PTT key must be pressed during telephone capability. talk-time to allow the voice message to be dispatched by the sending party. During this period, the sending party cannot 2.1 Mobile Radio hear or receive any incoming messages from the mobile radio. The mobile radio is a two-way communication gadget that Once the PTT button is released, the sender may hear the operates through radio frequencies. As such, the channel of response of the receiving party. information and messages in a mobile radio is variable. Used to be known as radiophone, the earlier versions of the mobile 2.3. Why do we need a mobile radio radio, were one-way communication systems used for The use of mobile radio in transportation, security, and broadcast. general operations makes communication fast, efficient and safe. It allows control centers to monitor location of vehicles Contemporary mobile radio systems can have as much as a and dispatch announcements to several receivers hundred channels and may be controlled by microprocessors. simultaneously. Additionally, the range of its area coverage is These types require the use of software to encode channels very high and is not dependent on a cellular network, which and operate their integrated functions. The mobile radio, also may fluctuate during emergency situations. known as a two-way radio system, allows the exchange of messages only with other mobile radios through push-to-talk Different types of mobile radio are portable and capable of (PTT) functions. A mobile radio also features wireless withstanding shock and severe weather conditions. Most transceivers, making mobile radios portable. Mobile radio countries impose certain requirements on the manufacture, systems may be used for communications in aircraft, ships, sale and use of two-radio systems. This helps ensure that the automobiles, and other vehicles. The power supply on which communication gadget functions according to standards and mobile radios run depend on the type of vehicle these are that its use does not interfere with other communication mounted on. systems. A mobile radio system is composed of a transceiver and 3. History of mobile radio microphone with a push-to-talk key. It has an antenna that links to the transceiver. Since most types of mobile radio are Early users of mobile radio equipment included transportation used in moving vehicles, where the surrounding noise can be and government. These systems used one-way broadcasting loud, some mobile radio types come with an external speaker. instead of two-way conversations. Railroads used medium Other models have headsets and microphones with noise- frequency range (MF) communications (similar to the AM reduction capabilities. broadcast band) to improve safety. Instead of hanging out of a locomotive cab and grabbing train orders while rolling past a 2.2. How does a mobile radio work? station, voice communications with rolling trains became Most mobile radios operate on a single band of frequency. possible. Radios linked the caboose with the locomotive cab. The radio transceiver contains transmit and receive Early police radio systems were initially one way using MF frequencies. Very high frequency (VHF) and ultra high frequencies above the AM broadcast band, (1.7 MHz). Some frequency (UHF) allow a mobile radio to operate on early systems talked back to dispatch on a 30-50 MHz link, maximum coverage. This means that its average operating (called crossband). range is from 150 to 470 MHz. Early mobile radios used amplitude modulation (AM) to so they could not transmit unless the vehicle ignition was on. convey intelligence through the communications channel. In Persons without a key to the vehicle could not transmit. time, problems with sources of electrical noise showed that Equipment had to be "type accepted", or technically approved, frequency modulation (FM) was superior for its ability to cope by the FCC before it could be offered for sale. In order to be with vehicle ignition and power line noise. The frequency type accepted, the radio set had to be equipped with an range used by most early radio systems, 25 to 50 MHz (vhf indicator light, usually green or yellow, that showed power "low band") is particularly susceptible to the problem of was applied and the radio was ready to transmit. Radios were electrical noise. This plus the need for more channels led to also required to have a lamp (usually red) indicating when the the eventual expansion of two-way radio communications into transmitter was on. These traits continue in the design of the VHF "high band" (150 to 174 MHz) and UHF (450 to 470 modern radios. MHz). The UHF band has since been expanded again. Early tube-type radios operated on 50 kHz channel spacing One of the major challenges in early mobile radio technology with plus-or-minus fifteen kilohertz modulation deviation. was that of converting the six or twelve volt power supply of This meant that the number of radio channels that could be the vehicle to the high voltage needed to operate the vacuum accommodated in the available radio frequency spectrum were tubes in the radio. Early tube-type radios used dynamotors - limited to a certain number, dictated by the bandwidth of the essentially a six or twelve volt motor that turned a generator to signal on each channel. provide the high voltages required by the vacuum tubes. Some early mobile radios were the size of a suitcase or had separate boxes for the transmitter and receiver. As time went on, power supply technology evolved to use first electromechanical vibrators, then solid-state power supplies to provide high voltage for the vacuum tubes. These circuits, called "inverters", changed the 6V or 12V direct current (DC) to alternating current (AC) which could be passed through a In the early 1970s, the California Department of Forestry transformer to make high voltage. requirement for 6-frequency transmit, 3-frequency receive, scanning, and a 5-tone burst encoder was unusual, leading to Examples of US 1950s-1960s tube-type mobile radios with no this custom-built mobile radio. transistors: Solid state equipment arrived in the 1960s, with more efficient • Motorola FMTRU-140D (dynamotor powered) circuitry and smaller size. Channel spacing narrowed to 20-30 • Motorola Twin-V, named for its "universal" 6 or 12 kHz with modulation deviation dropping to plus-or-minus five Volt power supply kilohertz. This was done to allow more radio spectrum • General Electric Progress Line (Early models without availability to accommodate the rapidly growing national "T-Power" power supply) group of two-way radio users. By the mid 1970s, tube-type • Kaar Engineering Model 501 transmitter power amplifiers had been replaced with high- power transistors. From the 1960s to the 1980s, large system The requirement that unauthorized persons be prohibited from users with specialized requirements often had custom built using the radio transmitter meant that many radios were wired radios designed for their unique systems. Systems with multiple tone encoders and more than two channels are • Motorola Astro Digital Spectra W9 unusual. Examples of US hybrid partially solid state mobile • Kenwood TK-690 radios: As use of mobile radio equipment has virtually exploded, • Motorola Motrac. channel spacing has had to be narrowed again to 12.5-15 kHz • Motorola MJ IMTS Car Telephone (1963) with modulation deviation dropping to plus-or-minus 2.5 • General Electric Transistorized Progress Line kilohertz. In order to fit into smaller, more economical • General Electric MASTR Professional and MASTR vehicles, today's radios are trending toward radically smaller Executive sizes than their tube-type ancestors.