The Sportsdesk, a daily round up of sports news, is broadcast at 5. On Saturday afternoons scores and results are updated from pm on the Sportsmix. From Wikipedia, the free encyclopedia. Radio in Scotland. Capital Scotland Heart Scotland. Radio Borders Central Air3 Fresh Air Subcity Radio.
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Get promoted. Decade 's 's 's 's 's 's 's 's 's 's. Waves on Waves. Radio waves in a vacuum travel at the speed of light. Air is thin enough that in the Earth's atmosphere radio waves travel very close to the speed of light. A 1 megahertz radio signal has a wavelength of Radio waves are more widely used for communication than other electromagnetic waves mainly because of their desirable propagation properties, stemming from their large wavelength.
The study of radio propagation , how radio waves move in free space and over the surface of the Earth, is vitally important in the design of practical radio systems.
Radio waves passing through different environments experience reflection , refraction , polarization , diffraction , and absorption. Different frequencies experience different combinations of these phenomena in the Earth's atmosphere, making certain radio bands more useful for specific purposes than others.
Practical radio systems mainly use three different techniques of radio propagation to communicate: . In radio communication systems, information is carried across space using radio waves.
At the sending end, the information to be sent, in the form of a time-varying electrical signal, is applied to a radio transmitter. In the transmitter, an electronic oscillator generates an alternating current oscillating at a radio frequency , called the carrier wave because it serves to "carry" the information through the air.
The information signal is used to modulate the carrier, altering some aspect of it, "piggybacking" the information on the carrier. The modulated carrier is amplified and applied to an antenna. The oscillating current pushes the electrons in the antenna back and forth, creating oscillating electric and magnetic fields , which radiate the energy away from the antenna as radio waves. The radio waves carry the information to the receiver location.
At the receiver, the oscillating electric and magnetic fields of the incoming radio wave push the electrons in the receiving antenna back and forth, creating a tiny oscillating voltage which is a weaker replica of the current in the transmitting antenna. The receiver first uses a bandpass filter to separate the desired radio station's radio signal from all the other radio signals picked up by the antenna, then amplifies the signal so it is stronger, then finally extracts the information-bearing modulation signal in a demodulator.
The recovered signal is sent to a loudspeaker or earphone to produce sound, or a television display screen to produce a visible image, or other devices. A digital data signal is applied to a computer or microprocessor , which interacts with a human user. The radio waves from many transmitters pass through the air simultaneously without interfering with each other. They can be separated in the receiver because each transmitter's radio waves oscillate at a different rate, in other words each transmitter has a different frequency , measured in kilohertz kHz , megahertz MHz or gigahertz GHz.
The bandpass filter in the receiver consists of a tuned circuit which acts like a resonator , similarly to a tuning fork. The resonant frequency is set equal to the frequency of the desired radio station. The oscillating radio signal from the desired station causes the tuned circuit to oscillate in sympathy, and it passes the signal on to the rest of the receiver.
Radio signals at other frequencies are blocked by the tuned circuit and not passed on. Radio waves are nonionizing radiation , which means they do not have enough energy to separate electrons from atoms or molecules , ionizing them, or break chemical bonds , causing chemical reactions or DNA damage.
The main effect of absorption of radio waves by materials is to heat them, similarly to the infrared waves radiated by sources of heat such as a space heater or wood fire. The oscillating electric field of the wave causes polar molecules to vibrate back and forth, increasing the temperature; this is how a microwave oven cooks food. However, unlike infrared waves, which are mainly absorbed at the surface of objects and cause surface heating, radio waves are able to penetrate the surface and deposit their energy inside materials and biological tissues.
For example, the 2. Radio waves have been applied to the body for years in the medical therapy of diathermy for deep heating of body tissue, to promote increased blood flow and healing.
More recently they have been used to create higher temperatures in hyperthermia treatment and to kill cancer cells. Looking into a source of radio waves at close range, such as the waveguide of a working radio transmitter, can cause damage to the lens of the eye by heating.
A strong enough beam of radio waves can penetrate the eye and heat the lens enough to cause cataracts.Nov 27, · Irgendwie eine Enttäuschung! Ich mödchte nicht wirklich viel umschreiben und lege direkt los. Jeder Künstler für sich mag wirklich eine super Leistung mit den Tracks abgegeben haben, aber mal ehrlich: Ich hatte mich wirklich als Käufer seit Vol.1 auf die neue FT 4/5.