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What is HD Radio?

written by: Ricky • edited by: Lamar Stonecypher • updated: 1/12/2011

Looking for information about HD Radio or looking for a list of HD stations in your area? Wondering how to get "high definition radio?" This article provides technical details and covers the pros and cons of HD Radio in the US.

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    To begin with, HD Radio is not the same as HD television. In the case of radio, the abbreviation HD does not stand for "high definition." It is a brand name and does not actually stand for anything specific. Since 1895, when Italian physicist and inventor Gugilelmo Marconi conducted his first experiments with wireless technology, this humble device has come a long way- AM and shortwave radio, FM radio, satellite radio, Internet radio, and now HD Radio.

    HD Radio, which has also been called "highly digital radio" by some, is a new radio format that provides additional features to the existing radio signals and is intended to make radio listening a more immersive experience. Some of the promises being made about this technology include better sound quality, more stations broadcasting in the same bandwidth, and additional information like artist and album information being included. HD Radio is being transmitted along with the existing formats (AM and FM), but the intention of the developers (iBiquity) is not to replace these formats.

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    What are the differences between Traditional Formats and HD Format?

    The primary differences between the traditional formats and HD format are:

    • Analog Waves vs. Digital Waves: The traditional formats (AM & FM) use analog radio waves while HD uses digital waves.

    The digital waves allow textual data like song lyrics, titles, sports, stock updates, etc. to be transmitted along.

    • Sound Quality: AM and FM signals are able to carry limited information whereas HD Radio is able to carry much more information, which is translated as a better quality of sound.

    Digital signals are less prone to multipath distortions, interruptions, and distortions, which reduces static and pops.

    • MultiCasting/ Multiplexing: HD Radio has to transmit multiple channels from a single frequency. If a frequency is multicasting, the HD Radio will alert the listener to the same and he can tune to the other channel using a button or dial on the radio.
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    How HD Radio Works

    The differences between the working of both formats are not much different. As in the case of a traditional radio, a transmitter is required at one end and a receiver at the other. The current HD technology available in the market allows addition of a single music channel and three extra talk channels without proving detrimental to sound quality. These extra stations are referred to as HD2 and HD3.

    When a radio station agrees to transmit HD signals, it is required to transmit digital signals along with analog signals. Breaking the operation into steps:

    • Compression of Digital Information: The digital signal is made to go through a computer that compresses the digital information.
    • Transmission: Both the unaffected analog information and the digital information are transmitted at the same time.
    • Reception: A conventional radio does not have the ability to receive HD Radio signals. To be able to enjoy HD Radio signals, it is imperative that a receiver be installed that allows reception of all three formats.
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    Is All Rosy in HD Land?

    Before you conclude after reading all the above description that HD radio is the cure for all ills related to radio transmission and is of the best quality ever made available to mankind, think again.

    Let's look at the flaws of HD, or rather I would prefer to call it the hype associated with HD, which tends to cloud the main issues related to its performance.

    Firstly the IBOC or "In-Band On-Channel" technology which is used to transmit digital and analog signals at same frequency, causes interference with adjacent channels, so much so that new acronyms have been coined (in pun) like In-Band Adjacent-Channel (IBAC) or even IBUZ due to the buzzing or humming noise it generates. The effect on FM is reduced or absent distant adjacent channel rejection if more local stations are running HD radio, which is particularly bothersome if the receiver locks onto a distant digital station's signal instead of the desired local analog FM signal.

    Yet supporters of HD argue that even though this "capture effect" is indeed applicable in case of FM channels, it is very unlikely that IBOC signals would cause interference in adjacent channels unless they were much weaker. Yet not only distance from the FM station is involved; characteristics like terrain and even time of the day act as spoilsports and cause the problem.

    Many AM stations have switched off IBOC because of the objectionable buzz or buzz-saw-like noise heard in adjacent channels in crowded urban areas.

    In the end it could be stated that though HD radio is an innovative idea, and practically seems to provide a much better audio quality for radio transmission, it is not yet so in practice. The practical limitations which have plagued the actual implementation of the HD systems have added a quantity of problems as great as the number of meager benefits of this so-called improved quality.

    It is high time that we perceive this technological development in light of the actual circumstances. Scientists, researchers, and broadcast engineers should try to find less expensive cures for the noise and interference so as to aid large scale adoption and implementation of this technology.

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    Finding an HD Radio Station in your Area

    HDRadio.com: Discover Stations in Your Market

    Ibiquity: Find a US HD Radio Station Near You

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