Monday, August 5, 2013

The Development of Digital Multimedia Broadcasting

Map of digital terrestrial televison broadcast...
Map of digital terrestrial televison broadcast standards: DVB-T, ATSC, ISDB, DMB-T/H. Successor to Image:PAL-NTSC-SECAM.svg. (Photo credit: Wikipedia)
The development of digital multimedia broadcasting

Satellite radio systems are actually part of a larger group of broadcasting mediums, which specialists refer to as Digital Multimedia Broadcasting or DMB. This digital transmission system is used in order to send data to different receivers such as radios, television sets or mobile phones and PDAs. There are two different ways of using digital multimedia broadcasting - S-DMB which is broadcasting via a satellite or T-DMB which uses terrestrial emitters. The complexity of the entire digital multimedia broadcasting field is huge. Out of all the features and characteristics digital broadcasting offers, satellite radio is probably the most spectacular as it generated immense interest and triggered an intense competition between the two main satellite radio broadcasters, Sirius and XM Radio. The development of satellite radio and other forms of digital broadcasting is spectacular because it offers two main qualities that terrestrial emitters are deficient in: quality and coverage. In the case of satellite radio, for example, the sound quality from a satellite broadcast is much higher than AM or FM broadcasts, as the hissing noises and transmission disturbances are eliminated.

Technical features of digital multimedia broadcasting - overview

Whether it refers to television, satellite radio or cell phone transmissions, digital multimedia broadcasting is based on the Eureka 147 DAB standard. Digital television uses the T-DMB which is made for transmissions on frequency bands III (VHF) and L (SHF). T-DMB is an ETSI standard (TS 102 427 and TS 102 428).
T-DMB uses MPEG-4 Part 10 (H264) for the video and MPEG-4 Part 3 BSAC or HE-AAC V2 for the audio.  When  it comes to satellite radio, there were a few issues to be resolved by the main satellite radio broadcasters. The satellite radio receiver needs to be in the line of sight of the satellite to receive the transmission – and there is the problem of having different landscaping objects block the direct transmission. Land based devices were installed in order to eliminate the lack of direct satellite transmission. Since the wider spectrum of broadcasts has to be covered, digital multimedia broadcasting uses OFDM-4DPSK modulation and a chip of T-DMB receiver is also provided by MPEG-2 Transport Stream De-multiplexer. This helps reduce the negative effects of shadowing and fading, present in many digital transmissions.

The future of digital multimedia broadcasting

The transfer from the analog world to the digital one is obvious in all fields of work. Since digital multimedia broadcasting is developing so quickly, there is a silent battle going on between the new age digital technology and the classic analog one. OF course, many compare the transition from the analog to the completely digital era with the way audio cassettes were replaced by CDs and later on even DVDs. However, the development of digital multimedia broadcasting is slower since it happens on so many levels at the same time. Digital television is taking us into new spaces that are basically hybrids of the features of regular TV and characteristics of the Internet. Satellite radio is also taking huge leaps forward, with more and more programs having satellite radio exclusivity. There are even discussion of moving events like the MLB exclusively on satellite radio, which would provide one of the first deadly strikes against terrestrial radio broadcasting. Digital data transmission is fast and accurate, and so far reality proves that the satellites used in order to facilitate broadcasting and reliable. Most digital multimedia broadcasting companies that own satellites also have backup ones ready to go in orbit and replace a defective one. Some other benefits of digital multimedia broadcasting recommend it as a next step in the development of broadcasting. From the consumer’s point of view, the quality and interactivity options of digital TV or satellite radio broadcasts are important features. Although most digital multimedia broadcasting channels and technologies are still complex and sometimes expensive, the evolution of digital broadcasting seems to be here to stay.

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Saturday, August 3, 2013

The Roots Of Radio Hobbyists

English: Cartoon showing a man receiving Morse...
English: Cartoon showing a man receiving Morse code during an amateur radio examination. (Photo credit: Wikipedia)
The Roots Of Radio Hobbyists

Radio hobbyists can play with their equipment all day without giving a thought to the origins of their hobby. Early radio hobbyists were part of something that was, at the time, new and fairly crazy.

After radio technology was stabilized, there was a steady growth of radio signaling in the fields of navigation of ships and for rescue operations. On the other hand, the amateur radio operators also started to dominate the air. The first documented and famous amateur wireless enthusiast was a then young man named Irving Vermilya born in 1890 when wireless transmission was being born. The young man since age 12 heard Marconi and built his own wireless transmission equipment and was often “heard” telegraphing with ships during that time. In 1911 he became a member of the Radio Club that had been formed. He got himself certified in 1912 when law mandated all wireless operators to be certified. In his own words,

This was pre-audio era, and communication was purely in Morse code. Irving then organized his own amateur group who had regular meetings monthly and would communicate daily wishing “GM” (good morning) and “GN” (good night), some of the first amateur jargon to be used. He also proceeds to describe in his series of articles published in QST magazine in 1917 as to how they managed to lay the telegraph lines and such and how they “drew juice” for the wireless operation from the electric lines instead of relying on batteries.

Meanwhile, apart from the “professionals” and “amateurs”, with audio wireless signal transmission there was a new revolution setting in. A Dutch engineer in Hague was the first to make regular wireless transmission via radio. This could be considered the first regular radio broadcast. After this there was slow development until the commercial radio stations came into being.

The requirement to be certified killed the enthusiasm in many amateurs, and the number of amateurs dwindled. But then after WWI, there was a boom. The first radio clubs were formed in 1909 and this was the beginning of the radio hobbies which included radio as a part of the hobby activity.

During the WWI the amateur radio operators were asked to stop their activity and dismantle the equipment. Radio operators in uniform helped in military communications. They got back on the air again by November 1919 again. A similar lull in amateur radio happened during Second World War and got back on air by 1946. After lots of battles over the frequency range that the amateurs can tune into, the amateur radio is here to stay!

At present there are more than 170,000 ham operators which is possibly not the complete picture. It is still increasing. So, with Irving Vermilya was born the amateur radio operation, since he was the first radio hobbyist. After lots of developments, including the discovery of the transistor which greatly decreased the size of the radio equipment, the old ways still remains which included “waiting for someone to signal”.

The rules to get oneself certified and licensed included a Morse code proficiency until the World Radiocommunication Conference in Geneva in 2003 that eliminated the need for Morse code proficiency from the licensure tests. Taking effect from February 23, 2007 the Morse code has been eliminated from the tests for amateur radio license tests.

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