Note: This article is one I wrote previously and posted on the Guangtan and Desheng forums. Later, Guangtan was shut down, and a version restoration on Desheng also lost several years' worth of articles, including this one, so it's essentially impossible to find online. However, there are now many radio enthusiasts on HamCQ, and I am re-posting this article for reference and correction purposes.
What frequency bands are used on American radios?
2016-02-22
We know that radios typically divide the spectrum into "bands" based on modulation type or frequency range. In common radios used in China, the main modulation types include amplitude modulation (AM).（AM）Related to frequency modulation（FM）. The amplitude modulation band typically includes shortwave.（SW）、Medium wave（MW）And long wave（LW）Some radios also have aviation band receivers.（AIR）In addition to the standard FM frequency range specified by national standards, some radios also offer FM frequency ranges for campuses or foreign countries, as well as audio-only TV channels.（TV）In recent years, digital broadcasting has emerged in some cities, and we have also seen some digital radios with "bands" for DAB and DAB+.
Are American radios also divided into frequency bands in this way? In fact, the International Telecommunication Union (ITU)（ITU）There are certain regulations regarding the use of radio frequencies globally. The allocation standards for FM broadcast bands in different countries are generally similar, but there are slight differences in frequency ranges, channel spacing, and step frequencies. The characteristics of US radio management policies determine that radios often include these public broadcast bands, as well as some special bands. In terms of digital broadcasting, due to factors such as technical patents, the use of different standards varies across countries. This article briefly introduces some rare American-specific bands and technologies found on radios in China.
Simulated broadcast
During the 1960s to 1990s, multi-band radios sold in Europe and America often included CB (Citizens Band), PB (Police/Public Service Band), and WB (Weather) bands.
CB civilian band —— This band, located around 27 MHz, is also known as the "11-meter band." Most countries in Europe and America have opened this frequency range for civilian radio voice communication. Within a certain power range, no license is required, and there are no restrictions on using this band for commercial activities. In the United States, this band has been divided into 40 frequencies, using AM modulation. During the 1970s, civilian radio stations (walkie-talkies) based on this band were widely used in American civilian life, particularly favored by long-haul truck drivers, becoming a tool for them to communicate and entertain themselves. Therefore, many radios also offer a "read-only" CB band. Later, with the popularity of mobile phones and the internet, the CB band is no longer popular among the general public, but some long-haul truck drivers still use it.
PB Police/Public Service Band — This band operates in the ultra-high frequency range.（VHF）It is typically divided into two segments: high (150-160 MHz) and low (39-45 MHz), primarily using FM modulation. Police radio stations mainly use frequencies within this band, and some government agencies also use this band to broadcast public safety information and emergency announcements. To facilitate the release of emergency broadcasts by governments while satisfying the public's curiosity about police activities (which is legal in most US states), this frequency band is also covered by many multi-band radios. With the digitization of police communication equipment and the updating of public safety notification mechanisms, the amount of public information available in the PB band has decreased significantly, and amateur radio enthusiasts are now able to receive more.（HAM）of Tonglian.
WB weather band — This band is also known as WX, and includes several frequencies around 162.5 MHz, using narrow-band FM modulation, specifically for use in North America. In the United States, this band contains "NOAA Weather Radio," which provides detailed local weather reports and forecasts, as well as serving as a government emergency broadcast channel. Because the frequency range of this band is small, many radios combine it with the PB band. Unlike the CB and PB bands, which are nearing obsolescence in mainstream markets, some radios in the United States still offer the WB band, and even some radios have the automatic power-on and automatic channel-switching function when receiving emergency information, highlighting its importance as a "lifeline."
Digital broadcasting
The DAB/DAB+ digital broadcasting standard, which is used in some cities in China, originated in Europe and is not used in the United States. The widely adopted digital broadcasting standard in the US is HD Radio. Additionally, satellite digital broadcasting has a certain market share in the US, while traditional FM broadcasting also incorporates some digital elements.
HD Radio "High Definition" broadcast — This technology is named after high-definition television.（HDTV）It is a patented technology of iBiquity. Unlike DAB/DAB+, which uses separate frequencies, HD Radio adds an OFDM modulated digital subcarrier near the existing AM/FM analog signals. This allows for "high-definition enhanced" audio quality similar to CD, while also supporting selective reception modes such as "one program, multiple preferences." The HD Radio technology has been adopted by many FM radio stations in cities across the United States. HD Radio receivers are primarily available in car stereos, GPS integrated radios, or home stereo systems. End users can receive HD Radio completely free of charge.
Sirius XM satellite radio —— This name serves as both the trademark for a satellite digital broadcasting platform and the name of the company that operates it. The company was formed through the merger of Sirius and XM, and after its competitors went out of business, it became the only remaining operating satellite broadcasting company globally, with signals primarily covering North America. Due to the combined technology of the two companies, Sirius XM's technical standards are not uniform. Its satellite carrier frequency is located near 2.3 GHz in the S band, and it also includes a ground relay network as an addition for urban areas. Currently, the platform offers over one hundred broadcasting programs, most of which require paid subscriptions. The primary receivers are car-based radios, but it also provides non-satellite listening modes based on internet or mobile applications.
RDS Broadcast Data System — This technology refers to an additional digital subcarrier added near the analog signal of existing FM radio, rather than a standalone frequency band. RDS typically includes information such as station call signs, program types, and names, which can be displayed on the receiver's screen for listeners to understand the broadcast content. For car radios, RDS also provides advanced features such as traffic information, clock synchronization, and automatic switching between radio frequencies across cities. RDS technology is widely used in FM radio stations in Europe and America, and it is supported by car radios, mobile phone built-in radios, and high-end portable radios. Due to differences in listening habits, this technology has not been widely adopted in Chinese FM radio stations.
闽ICP备2021006864号-7
闽公网安备35020602002794号