Why Have A Manuall?

Radio Definition, History, & Facts

In order to receive the weak signals from distant spacecraft, satellite ground stations use large parabolic "dish" antennas up to 25 metres in diameter and extremely sensitive receivers. Portions of the UHF, L, C, S, ku and ka band are allocated for space communication. A radio link that transmits data from the Earth's surface to a spacecraft is called an uplink, while a link that transmits data from the spacecraft to the ground is called a downlink. Bluetooth – a very short-range wireless interface on a portable wireless device used as a substitute for a wire or cable connection, mainly to exchange files between portable devices and connect cellphones and music players with wireless headphones.

So there is an incentive to employ technology to minimize the bandwidth used by radio services. The existence of radio waves was first proven by German physicist Heinrich Hertz on November 11, 1886. The first commercial radio broadcast was transmitted on November 2, 1920 when the live returns of the Harding-Cox presidential election were broadcast by Westinghouse Electric and Manufacturing Company in Pittsburgh, under the call sign KDKA. Canada when station XWA in Montreal began transmitting experimentally in September 1919 and on a regular schedule the next year. (The first commercially sponsored stations in Canada appeared in 1922.) The first British station offered two daily half-hour programs of talk and music from Chelmsford in 1919–20.

But the transmission areas are limited in the radius around the transmitter. The receiving devices do not communicate back to the transmitter. For internet Radio, an internet connection between the transmitter and the receiver, is actually necessary.

The transmitter emits a narrow beam of radio waves which is swept around the surrounding space. When the beam strikes a target object, radio waves are reflected back to the receiver. Since radio waves travel at a constant speed close to the speed of light, by measuring the brief time delay between the outgoing pulse and the received "echo", the range to the target can be calculated. The targets are often displayed graphically on a map display called a radar screen. Doppler radar can measure a moving object's velocity, by measuring the change in frequency of the return radio waves due to the Doppler effect. Digital Radio Mondiale is a competing digital terrestrial radio standard developed mainly by broadcasters as a higher spectral efficiency replacement for legacy AM and FM broadcasting.

It transmits audio as a digital signal rather than an analog signal as AM and FM do. DAB has the potential to provide higher quality sound than FM , has greater immunity to radio noise and interference, makes better use of scarce radio spectrum bandwidth and provides advanced user features such as electronic program guides. Its disadvantage is that it is incompatible with previous radios so that a new DAB receiver must be purchased.