Radio broadcasting

Radio broadcasting is a unidirectional wireless transmission over radio waves intended to reach a wide audience. Stations can be linked in radio networks to broadcast a common radio format, either in broadcast syndication or simulcast or both. Audio broadcasting also can be done via cable radio, local wire television networks, satellite radio, and internet radio via streaming media on the Internet. The signal types can be either analog audio or digital audio.

In 2009, there were 3,494 radio broadcasting stations in the United States.

History

The earliest radio stations were simply radiotelegraphy systems and did not carry audio. For audio broadcasts to be possible electronic detection and amplification devices had to be incorporated.

The thermionic valve was invented in 1904 by the English physicist John Ambrose Fleming. He developed a device he called an "oscillation valve" (because it passes current in only one direction). The heated filament, or cathode, was capable of thermionic emission of electrons that would flow to the plate (or anode) when it was at a higher voltage. Electrons, however, could not pass in the reverse direction because the plate was not heated and thus not capable of thermionic emission of electrons. Later known as the Fleming valve, it could be used as a rectifier of alternating current and as a radio wave detector. This greatly improved the crystal set which rectified the radio signal using an early solid-state diode based on a crystal and a so-called cat's whisker. However, what was still required was an amplifier.

FM broadcasting

FM broadcasting is a VHF broadcasting technology, pioneered by Edwin Howard Armstrong, which uses frequency modulation (FM) to provide high-fidelity sound over broadcast radio. The term "FM band" describes the frequency band in a given country which is dedicated to FM broadcasting. This term is slightly misleading, as it equates a modulation method within a range of frequencies.

Broadcast bands

Throughout the world, the FM broadcast band falls within the VHF part of the radio spectrum. Usually 87.5 to 108.0 MHz is used, or some portion thereof, with few exceptions:

The frequency of an FM broadcast station (more strictly its assigned nominal center frequency) is usually an exact multiple of 100 kHz. In most of South Korea, the Americas, the Philippines and the Caribbean, only odd multiples are used. In some parts of Europe, Greenland and Africa, only even multiples are used. In the UK odd or even are used. In Italy, multiples of 50 kHz are used. There are other unusual and obsolete standards in some countries, including 0.001, 0.01, 0.03, 0.074, 0.5, and 0.3 MHz. However, to minimise cross-channel interference, stations operating from the same or geographically close transmitters tend to keep to at least a 0.5 MHz frequency separation even when closer spacing is technically permitted, with closer tunings reserved for more distantly spaced transmitters as potentially interfering signals are already more attenuated and so have less effect on neighbouring frequencies. RCA stereo models use multiples of 0.2 MHz, starting at 87.50 and ending at 107.90.

Raspberry Pi

The Raspberry Pi is a series of credit card–sized single-board computers developed in England, United Kingdom by the Raspberry Pi Foundation with the intention of promoting the teaching of basic computer science in schools and developing countries. The original Raspberry Pi and Raspberry Pi 2 are manufactured in several board configurations through licensed manufacturing agreements with Newark element14 (Premier Farnell), RS Components and Egoman. The hardware is the same across all manufacturers.

All Raspberry Pis include the same VideoCore IV GPU, and either a single-core ARMv6-compatible CPU or a newer ARMv7-compatible quad-core one (in Pi 2); and 1 GB of RAM (in Pi 2), 512 MB (in Pi 1 models B and B+), or 256 MB (in models A and A+, and in the older model B). They have a Secure Digital (SDHC) slot (models A and B) or a MicroSDHC one (models A+, B+, and Pi 2) for boot media and persistent storage. In 2014, the Raspberry Pi Foundation launched the Compute Module, for use as a part of embedded systems for the same compute power as the original Pi. In early February 2015, the next-generation Raspberry Pi, Raspberry Pi 2, was released. That new computer board is initially available only in one configuration (model B) and has a quad-core ARM Cortex-A7 CPU and 1 GB of RAM with remaining specifications being similar to those of the previous generation model B+. The Raspberry Pi 2 retains the same US$35 price point of the model B, with the US$20 model A+ remaining on sale. In November 2015, the Foundation launched the Raspberry Pi Zero, a smaller product priced at US$5.

Radio

Radio is the use of radio waves is to carry information, such as sound, by systematically modulating some property of electromagnetic energy waves transmitted through space, such as their amplitude, frequency, phase, or pulse width. When radio waves strike an electrical conductor, the oscillating fields induce an alternating current in the conductor. The information in the waves can be extracted and transformed back into its original form.

Radio systems need a transmitter to modulate (change) some property of the energy produced to impress a signal on it, for example using amplitude modulation or angle modulation (which can be frequency modulation or phase modulation). Radio systems also need an antenna to convert electric currents into radio waves, and vice versa. An antenna can be used for both transmitting and receiving. The electrical resonance of tuned circuits in radios allow individual stations to be selected. The electromagnetic wave is intercepted by a tuned receiving antenna. A radio receiver receives its input from an antenna and converts it into a form usable for the consumer, such as sound, pictures, digital data, measurement values, navigational positions, etc. Radio frequencies occupy the range from a 3 kHz to 300 GHz, although commercially important uses of radio use only a small part of this spectrum.

Halla Bol

Halla Bol (Raise Your Voice) is a Hindi drama film released on 11 January 2008, and directed by Rajkumar Santoshi. Halla Bol stars Ajay Devgan and Vidya Balan in pivotal roles and a number of celebrities from the Hindi film industry appear as themselves. Produced by Samee Siddiqui, the film's score and soundtrack was composed by Sukhwinder Singh, while Nataraja Subramanian and Steven Bernard were the cinematographer and editor respectively.

The film touches upon the Jessica Lall murder case, Aamir Khan's involvement with the Narmada Bachao Andolan, the Right to Information Act, and public participation in fighting corruption. It also references the theatre group Jan Natya Manch, whose leader, theatre activist Safdar Hashmi, was killed by political rivals while performing a street play by the same name, Halla Bol!, in 1989.

Plot

Ashfaque (Ajay Devgn) is a small town boy aspiring to be a film star in the Hindi film industry. He joins a street theatre group run by a reformed dacoit Sidhu (Pankaj Kapoor), who uses street theatre as a medium to bring about an awakening in the masses. Ashfaque struggles to give a creative vent to the actor in him in order to realise his dreams. Ashfaque's determined struggle pays off and he gets a break in films. He gets a new screen name – Sameer Khan. With the passage of time, he moves up the success ladder in a very short time.