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Medium wave

Medium wave (MW), also known as medium frequency (MF) band 6, encompasses radio frequencies from 300 kHz to 3 MHz, corresponding to wavelengths of 1,000 to 100 meters, and is predominantly allocated for amplitude modulation (AM) broadcasting worldwide.^[1] This band enables reliable groundwave propagation during the day for local coverage up to approximately 150-200 km over average terrain, while nighttime skywave reflections from the ionosphere extend signals over thousands of kilometers, facilitating both regional and international transmissions.^[2] The broadcasting allocations within the medium wave band vary by ITU region: in Region 1 (Europe, Africa, former USSR, Middle East) and Region 3 (Asia, Australasia), it spans roughly 526.5-1,606.5 kHz with 9 kHz channel spacing; in Region 2 (Americas), it covers 535-1,605 kHz with a 10 kHz spacing, extending to 1,705 kHz for some stations.^[3] Primarily utilized for speech and music radio, medium wave supports thousands of stations globally, including public service announcements, news, and entertainment, with notable applications in navigation aids like non-directional beacons (NDBs) and emergency communications.^[4] In North America alone, over 4,500 AM stations operate in this band, regulated by bodies such as the FCC to manage interference through power limits and directional antennas.^[4] Historically, medium wave broadcasting emerged in the early 20th century, with Reginald Fessenden's 1906 Christmas Eve transmission of voice and music marking one of the first AM broadcasts, followed by commercial milestones like KDKA's 1920 election coverage launch.^[5] By the 1930s, it had become the cornerstone of mass media during radio's "Golden Age," reaching 60% of U.S. households and generating substantial advertising revenue, though it faced challenges from FM's superior audio quality post-World War II.^[5] Today, while digital alternatives and spectrum pressures have reduced its dominance in some markets, medium wave remains vital in developing regions, for long-distance listening, and as a resilient platform during disasters due to its extensive coverage without reliance on repeaters.^[4]

Fundamentals

Definition and Frequency Range

Medium wave (MW) refers to the portion of the radio spectrum spanning frequencies from 300 kHz to 3 MHz, which corresponds to wavelengths ranging from 1,000 meters to 100 meters.^[6] This band is primarily utilized for amplitude modulation (AM) broadcasting, navigation, and other services that benefit from its propagation characteristics.^[7] The International Telecommunication Union (ITU) officially designates this range as the medium frequency (MF) band, numbered as band 6 in its nomenclature for telecommunications frequencies.^[6] The term "medium wave" originated in the early 20th century as part of a wavelength-based classification system for radio bands, predating the modern frequency-based ITU standards, and remains in common use particularly for broadcasting applications within the MF band.^[7] The relationship between wavelength \lambda (in meters) and frequency f (in hertz) for radio waves in free space is given by the formula

\lambda = \frac{c}{f},

where c is the speed of light, approximately $3 \times 10^8 m/s.^[8] For example, at the lower end of the band, a frequency of 300 kHz (f = 300 \times 10^3 Hz) yields \lambda = 1000 m, calculated as \lambda = 3 \times 10^8 / 300 \times 10^3. Similarly, at the upper end, 3 MHz (f = 3 \times 10^6 Hz), \lambda = 100 m. These hectometric wavelengths reflect the band's position in the spectrum, bridging longer and shorter wave categories.^[8] Medium wave is distinguished from adjacent bands by its frequency boundaries: it lies above the low frequency (LF) band, which extends from 30 kHz to 300 kHz, and below the high frequency (HF) band, starting at 3 MHz.^[6] This positioning influences its typical ground-wave and sky-wave propagation behaviors, though detailed propagation is addressed elsewhere.^[7]

Historical Development

The origins of medium wave technology trace back to the late 19th century, when inventors began experimenting with electromagnetic waves for wireless communication. Guglielmo Marconi conducted pioneering work in wireless telegraphy starting in 1894, demonstrating the transmission of Morse code signals over distances using electromagnetic waves in the medium frequency range, which laid the groundwork for radio development.^[9]^[10] By 1906, Reginald Fessenden achieved the first amplitude-modulated voice and music transmission from Brant Rock, Massachusetts, on December 24, marking a breakthrough in broadcasting intelligible audio over medium wave frequencies.^[11] Following World War I, medium wave broadcasting saw rapid commercialization in the 1920s, transitioning from experimental telegraphy to public entertainment and news. The establishment of KDKA in Pittsburgh on November 2, 1920, by Westinghouse Electric, represented the world's first scheduled commercial radio broadcast, covering the Harding-Cox presidential election results and initiating widespread AM adoption.^[12] Amplitude modulation became the standard for medium wave transmissions during this decade, enabling reliable audio broadcasting as vacuum tube technology advanced.^[13] International coordination efforts culminated in the 1927 International Radiotelegraph Conference in Washington, D.C., which allocated frequency bands for broadcasting, including the medium wave spectrum (300–3000 kHz), to reduce interference and facilitate global expansion.^[14] The 1930s through the 1950s marked the golden age of medium wave radio, with AM stations proliferating as a primary medium for news, drama, and music in households worldwide. By the end of the 1930s, radio ownership had surged, with millions tuning in daily for live programming that shaped popular culture.^[15] Post-World War II, medium wave infrastructure expanded significantly in developing regions, providing accessible communication where wired or higher-frequency options were limited, supported by international aid and technological transfers.^[16] Medium wave's prominence began declining in the 1960s as frequency modulation (FM) offered superior audio quality and television captured visual entertainment audiences, leading many music stations to migrate to FM.^[16] Despite this shift in developed markets, medium wave persisted in areas with limited infrastructure, valued for its long-distance propagation and low-cost receivers, continuing to serve rural and remote communities globally.^[16]

Technical Characteristics

Spectrum Allocation and Channel Spacing

The medium wave spectrum for broadcasting is allocated by the International Telecommunication Union (ITU) across its three regions, with variations in frequency range and channel spacing to accommodate regional needs while ensuring compatibility. In ITU Region 1 (Europe, Africa, the Middle East, and parts of Asia) and Region 3 (Asia, Australia, and the southwestern Pacific), the primary broadcasting band spans 531 kHz to 1602 kHz, utilizing 9 kHz channel spacing. This arrangement stems from the Geneva Plan of 1975 (GE75), which established coordinated frequency assignments for medium frequency broadcasting in these regions to facilitate international harmony. In contrast, ITU Region 2 (the Americas) employs a band from 530 kHz to 1710 kHz with 10 kHz channel spacing, as defined in the ITU Radio Regulations and implemented through regional agreements like the North American Regional Broadcasting Agreement (NARBA). These differences allow for optimized use of the spectrum, with Region 2's wider spacing accommodating historical broadcasting practices in the Americas.^[3]^[17]^[18] Channel spacing in the medium wave band is determined to minimize co-channel and adjacent-channel interference, given that amplitude-modulated (AM) signals typically occupy a bandwidth of approximately 10 kHz—comprising a carrier and two sidebands each extending up to 5 kHz for standard audio frequencies. The 9 kHz spacing in Regions 1 and 3 thus limits effective audio bandwidth to about 4.5 kHz per channel to prevent overlap, while the 10 kHz spacing in Region 2 permits up to 5 kHz audio without significant adjacent-channel intrusion. This design balances spectrum efficiency with signal quality, as narrower spacing enables more channels within the limited band but requires stricter modulation controls to avoid beat frequencies and distortion from nearby stations. For instance, the channel bandwidth B can be expressed as B = 2 \times f_{\max}, where f_{\max} is the maximum audio frequency (e.g., 4.5 kHz for 9 kHz spacing), ensuring the total signal fits within the allocated interval.^[19] Within these allocations, stations are assigned classes based on operating hours, power, and intended coverage to further reduce interference. Clear channels support high-power, unlimited-hour operations for wide-area service, while regional and local classes limit power and hours for more confined coverage. In North America (Region 2), for example, Class A stations on clear channels operate at powers between 10 kW and 50 kW daytime (with potential nighttime reductions), enabling primary service over large areas without co-channel competitors. Regional (Class B) and local (Class C/D) assignments use lower powers—up to 50 kW for Class B but often 1 kW or less for locals—and may share channels or restrict nighttime operations to protect distant clear-channel stations. These classes ensure equitable spectrum use by prioritizing interference protection ratios, such as 26 dB for adjacent channels.^[20]^[21] International coordination of medium wave allocations occurs through ITU World Radiocommunication Conferences (WRCs), which revise the Radio Regulations to harmonize global and regional plans. The 1979 World Administrative Radio Conference in Geneva played a key role by incorporating updates to frequency allocations and planning procedures, building on prior regional agreements like GE75 to address evolving broadcasting demands and interference issues across borders. Subsequent WRCs, such as those in 1992 and beyond, have refined these frameworks to incorporate digital technologies while maintaining analog compatibility.^[22]^[17]

Propagation Behavior

Medium wave signals propagate through two primary mechanisms: ground wave and sky wave, each dominant under different conditions and contributing to the characteristic coverage patterns of medium frequency broadcasting. Ground wave propagation is the predominant mode during daytime hours, consisting of the direct wave from transmitter to receiver and the surface wave that diffracts along the Earth's surface, enabling signals to follow the planet's curvature. This mode typically supports reliable reception over distances of 100 to 200 km, though the exact range varies with transmitter power, antenna efficiency, frequency, and terrain characteristics. Lower frequencies within the medium wave band (closer to 0.5 MHz) generally achieve greater distances than higher ones (near 1.6 MHz) due to reduced attenuation from ground losses. Propagation quality is highly dependent on soil conductivity; conductive surfaces like seawater or wet soil facilitate longer ranges by minimizing energy absorption, whereas dry or rocky terrains increase losses and shorten effective coverage. A simplified approximation for ground wave range under ideal conditions is given by d \approx 2.4 \sqrt{P} \cdot f^{-0.15}, where d is the distance in km, P is the radiated power in kW, and f is the frequency in MHz; this model highlights the scaling with power and mild inverse dependence on frequency but requires adjustments for real-world ground parameters.^[23] Sky wave propagation becomes significant at night, allowing long-distance (DX) reception by reflecting signals off ionized layers in the ionosphere, primarily the E and F layers (at altitudes of approximately 90-150 km and 150-500 km, respectively), with the D layer (60-90 km) playing a disruptive role during the day. Signals can skip over intermediate zones, achieving reception distances exceeding 1,000 km, often via single- or multi-hop paths where the wave bounces between the ionosphere and ground. However, this mode is prone to fading and variability, as signal strength fluctuates due to interference between direct sky waves and residual ground waves, as well as multipath effects from multiple reflection paths.^[24]^[25]^[26] Several factors influence medium wave propagation reliability. During daylight, the D layer absorbs medium frequency signals attempting sky wave paths, effectively suppressing long-distance reception and confining coverage to ground waves; this absorption diminishes at night as the D layer recombines and fades. Atmospheric and man-made noise, including lightning-induced static and urban interference, further degrade signal-to-noise ratios, particularly for weaker sky wave signals. Solar activity exacerbates fading through enhanced ionization that alters reflection heights and absorption rates, while propagation is also affected by noise from natural sources like thunderstorms. Seasonal and diurnal variations play a key role: winter nights favor DX reception due to longer darkness periods and reduced D-layer absorption from lower solar angles, contrasting with summer's increased interference and shorter nights.^[24]

Audio Quality and Modulation

Medium wave broadcasting primarily employs amplitude modulation (AM), where the amplitude of a high-frequency carrier wave is varied in accordance with the instantaneous amplitude of the audio signal, while the carrier frequency remains constant. This modulation technique allows the transmission of audio content in the range of approximately 20 Hz to 20 kHz, but practical implementations limit the audio bandwidth to about 5-10 kHz to accommodate channel spacing and minimize interference. The standard form used is double-sideband (DSB) AM with a full carrier, which occupies a bandwidth roughly twice that of the modulating audio signal plus the carrier frequency itself.^[27] The audio quality in medium wave AM is inherently limited compared to frequency modulation (FM) in higher bands, primarily due to susceptibility to noise and interference from atmospheric sources, man-made signals, and propagation effects. Typical signal-to-noise ratios (SNR) for AM receivers range from 26 dB at sensitivity thresholds to at least 40 dB under stronger signal conditions, resulting in audible hiss and reduced fidelity, especially in noisy environments. The SNR is defined as SNR = P_signal / P_noise, where P_noise is often dominated by atmospheric disturbances like lightning-induced static in the medium wave band. Additionally, selective fading from multipath propagation can introduce phase distortions, leading to audio distortion and further degrading perceived quality. Variants like double-sideband suppressed-carrier (DSB-SC) AM, which eliminate the carrier to improve power efficiency, are not commonly used in broadcasting because they require complex synchronous detection in receivers, incompatible with simple envelope detectors found in consumer AM radios.^[28] Historically, medium wave transmissions have been monophonic since the early 20th century, with audio standards focused on voice and basic music reproduction; experimental stereo systems emerged only in the late 1970s and 1980s through FCC evaluations, but monophonic remained the norm for compatibility.^[29] These constraints prioritize robust coverage over high-fidelity audio, making AM suitable for talk radio and regional broadcasting rather than music-centric formats.

Antennas and Reception

Transmitting Antennas

Medium wave transmitting antennas are predominantly vertical monopoles, designed to produce vertically polarized waves that propagate effectively via ground waves over the 300 kHz to 3 MHz band.^[30] A quarter-wave monopole, resonant at the operating frequency, typically measures 50 to 250 meters in height, though lower-frequency applications may require structures up to 500 meters tall for optimal performance.^[30] These are often implemented as guyed towers to provide structural stability against wind and mechanical stresses, with the base insulated from ground to allow series or shunt feeding.^[30] To reduce physical height while maintaining electrical length, top-loaded designs incorporate capacitive hats, such as folded monopoles or umbrella-like structures, which increase the effective height and improve current distribution along the radiator.^[30] This top loading enhances radiation efficiency by elevating the average current height, particularly beneficial for shorter towers under 90 electrical degrees, where uniform current distribution would otherwise be suboptimal.^[30] Directional arrays are employed to shape the radiation pattern, minimizing interference by creating nulls in undesired directions while directing power toward target areas.^[30] Common configurations include four-tower arrays, arranged in parallelograms or in-line patterns with spacings of 90 to 180 electrical degrees, where phase shifts and amplitude adjustments between towers achieve precise control.^[31] These arrays can provide gains of 3 to 6 dB over omnidirectional monopoles by concentrating energy, as demonstrated in high-power installations like the four-tower system at Trans World Radio's Bonaire facility.^[31] Antenna efficiency in medium wave is critically influenced by the ground plane, which serves as the counterpoise for the monopole and minimizes losses from soil conductivity.^[32] Poor soil conditions can introduce significant ohmic losses, resulting in efficiencies as low as 20 to 30 percent in the medium frequency band due to power dissipation in the earth. For short monopoles (height h << λ/4), the radiation resistance is approximated by the formula:

R_\text{rad} \approx 40 \left( \pi \frac{h}{\lambda} \right)^2 \, \Omega

where h is the antenna height and λ is the wavelength; this low resistance exacerbates efficiency challenges when combined with ground losses.^[33] These antennas are engineered to handle high powers, up to 500 kW or more, to support long-distance broadcasting.^[34] Detuning networks, such as antenna tuning units, enable operation on non-resonant frequencies by matching impedance and compensating for variations in the radiation pattern across the medium wave spectrum.^[34]

Receiving Antennas

The most common receiving antennas for medium wave in consumer and hobbyist applications are ferrite loopsticks integrated into portable radios. These compact designs consist of a coil wound around a ferrite rod, which concentrates magnetic flux to enable efficient reception in a small form factor, typically measuring just a few centimeters in length. Their directional nature arises from the rod's orientation, providing a figure-of-eight radiation pattern in the horizontal plane that allows users to null interference from unwanted directions by rotating the radio. This makes them particularly suitable for urban environments with high noise levels.^[35]^[36] For enhanced performance, hobbyists often employ external long wire antennas, which are simple, non-resonant wires typically 25 meters or longer, connected to the receiver via a high-impedance transformer. These provide greater effective length and thus higher gain compared to internal loopsticks, capturing more of the electric field component of the signal. Dipole configurations, such as shortened or folded variants, can also be used for balanced reception, offering improved signal strength in open areas. However, their effectiveness depends on height above ground and orientation to minimize common-mode currents on the feedline.^[37] Key performance metrics for medium wave receiving antennas include sensitivity and selectivity. Good consumer receivers paired with these antennas achieve sensitivities of 10–50 μV, enabling detection of weak signals above atmospheric noise. Selectivity is determined by the Q-factor of the tuned LC circuits in the antenna or front-end, where higher Q values (typically 50–300) narrow the bandwidth to reject adjacent-channel interference, with Q defined as the ratio of inductive reactance to resistance. The figure-of-eight pattern of loop antennas further aids selectivity by providing deep nulls (up to 70 dB) for directional interference rejection. Propagation challenges, such as groundwave attenuation over distance, exacerbate the need for high sensitivity in weak-signal conditions.^[38]^[36]^[39] In advanced hobbyist setups for DXing distant medium wave stations, Beverage antennas are favored, consisting of a single long, low horizontal wire (3–5 meters high) terminated with a resistor to create a traveling-wave unidirectional pattern. These are typically 1–2 km in length—several wavelengths at medium wave frequencies—for optimal directivity and signal-to-noise ratio, pointing along the great circle path to the target. To counter ohmic losses in such extended wires, active preamplifiers with low-noise amplifiers are often inserted near the feedpoint, boosting the signal before transmission line attenuation.^[40]^[41] Limitations of receiving antennas in mobile contexts, such as vehicle-mounted whips, stem from their small electrical size relative to the wavelength, leading to poor efficiency and weak signal capture. The isotropic radiator assumption fails here, as these compact antennas exhibit low radiation resistance and high Q-factors that restrict bandwidth, resulting in reduced gain and vulnerability to noise. For small loop antennas, the inefficiency arises from their small size relative to the wavelength, underscoring challenges at medium wave frequencies.^[36]^[39]

Regional Broadcasting Practices

North America

In North America, medium wave (MW) broadcasting operates within a regulatory framework established by the Federal Communications Commission (FCC) in the United States, with coordinated agreements through the North American Agreement on Medium Wave Broadcasting for Canada and Mexico. The FCC allocates the AM band from 540 kHz to 1700 kHz using 10 kHz channel spacing, resulting in 117 primary channels divided into clear, regional, and local categories to manage interference and coverage. Clear channels are reserved for high-power Class A stations to provide wide-area service without co-channel interference, regional channels support medium-distance coverage for Class B and C stations, and local channels limit power for community service in Class D operations. In the 1990s, the FCC introduced the expanded band from 1610 kHz to 1700 kHz, adding 10 channels to accommodate growing demand and increase capacity by approximately 9% overall, though this was intended to support relocation of existing stations for better spectrum efficiency.^[42] Usage patterns in the region emphasize 24-hour operations focused on talk, news, and sports programming, with 4,360 licensed AM stations in the US as of mid-2025 serving diverse audiences.^[43] Clear-channel stations dominate long-distance propagation, exemplified by WGN in Chicago operating at 50 kW on 720 kHz to reach across the continent, particularly at night. Daytime power is capped at 50 kW for most classes to prevent excessive interference, enabling reliable coverage over hundreds of miles. Historically, Mexican border stations, known as "X-stations" or border blasters, emerged in the 1930s near the US border with call signs starting with "X," using powers up to 250 kW or more to target American listeners and bypass FCC restrictions on advertising and content, influencing cross-border cultural exchange until international treaties curtailed them in the 1980s.^[20]^[21]^[44]^[45] Culturally, MW radio plays a vital role in emergencies through the Emergency Alert System (EAS), where stations relay National Oceanic and Atmospheric Administration (NOAA) warnings and other alerts during disasters, maintaining operations even without commercial power. Listenership declined sharply since the 1980s as music formats migrated to FM for superior audio quality, reducing AM's share to primarily non-music content. However, in the 2020s, AM has seen renewed advocacy for inclusion in vehicles, particularly electric models facing removal due to electromagnetic interference from batteries and motors, with congressional mandates proposed to preserve it as a public safety tool amid the shift to digital media.^[46]^[47]^[48]^[49]

Europe

In Europe, medium wave broadcasting operates within ITU Region 1 standards, utilizing the frequency band from 531 kHz to 1602 kHz with 9 kHz channel spacing, providing approximately 120 channels for allocation.^[50] These allocations are governed by the Geneva Frequency Plan of 1975, which coordinates shared frequencies among countries to minimize interference through specified power levels, directional antennas, and usage patterns.^[51] The European Broadcasting Union (EBU) supports these ITU frameworks, promoting harmonized technical standards for public service broadcasters across the continent.^[52] The broadcasting landscape in Europe has historically been dominated by public service stations, delivering national and regional programming to wide audiences, though medium wave usage has significantly declined since the 2010s. For instance, France Inter, a flagship public station, formerly broadcast on multiple medium wave frequencies such as 675 kHz before ceasing analog transmissions in 2015 as part of cost-saving measures by Radio France.^[53] Similarly, the BBC operated medium wave services for Radio 4 on frequencies like 198 kHz (longwave adjacent) and others, but shut down all nine medium wave transmitters in April 2024 to focus on FM, DAB, and digital platforms.^[54] At its peak, Europe hosted over 1,000 medium wave stations, but by 2024, fewer than 100 remain active, with more than 20 countries, including France, the Netherlands, and much of Scandinavia, having fully ceased AM operations.^[55] The United Kingdom plans further medium wave reductions, with the BBC aiming for an online-only model by the 2030s, potentially ending all remaining analog services.^[56] Europe's dense population and high station concentration exacerbate interference challenges on medium wave, particularly at night when skywave propagation causes signals to overlap across borders, complicating reception in urban areas.^[57] This has led to medium wave's frequent use for multilingual international services, such as those from NEXUS-IBA on 1323 kHz, targeting audiences in multiple languages across Western Europe.^[50] In the 2020s, efforts to transition to digital have included pilots of DRM (Digital Radio Mondiale) technology on medium wave, with ongoing tests in the Czech Republic on 954 kHz and other European countries to enable stereo audio and data services without full spectrum overhaul.^[58] Regulatory shifts in the European Union emphasize spectrum efficiency amid broadcasting's decline, with directives encouraging reallocation of underutilized medium frequency bands for non-broadcasting applications, though primary focus remains on higher bands for mobile services through 2030.^[59] The EBU and CEPT advocate for coordinated planning to support digital transitions like DRM while preserving emergency and international broadcasting roles for medium wave.^[60]

Asia and Other Regions

In Asia, under ITU Region 3, medium wave broadcasting operates with 9 kHz channel spacing across the band from 526.5 to 1606.5 kHz, accommodating a dense network of stations to serve diverse populations.^[61] Japan utilizes frequencies from 531 to 1602 kHz, supporting approximately 50 AM stations, including networks like NHK, many of which are undergoing trial suspensions in 2024-2025 to facilitate a potential shift to FM broadcasting by 2028.^[62]^[63] In China, state-controlled broadcasting dominates the medium wave spectrum, with China National Radio 1 (CNR1) airing on multiple frequencies including 630 kHz, 855 kHz, 900 kHz, and 1116 kHz to propagate official news and programming across the country.^[64] India's All India Radio maintains 122 medium wave transmitters, many dedicated to rural areas where they deliver agricultural updates, education, and entertainment to remote communities with limited access to other media.^[65] Beyond Asia, medium wave practices vary by region, reflecting local infrastructure and regulatory frameworks. In Africa, broadcasting infrastructure remains limited in many areas due to economic constraints, yet medium wave persists as a key medium for news dissemination, with international services like Radio France Internationale relaying programs via local partners to reach underserved populations.^[66] Latin America follows Region 2 standards with 10 kHz channel spacing from 530 to 1700 kHz, similar to North America, but faces challenges from high-power pirate operations that disrupt licensed signals, particularly in urban fringes.^[67] Australia employs 9 kHz spacing, with the Australian Broadcasting Corporation (ABC) operating national medium wave stations such as 612 kHz in Brisbane and 792 kHz in regional areas to ensure broad coverage.^[68] Across these regions, medium wave radio remains essential in low-literacy and developing areas, serving as an accessible tool for information, education, and entertainment where print or digital alternatives are scarce.^[69] In the 2020s, challenges include frequent power outages disrupting transmissions in parts of Southeast Asia and Africa, though growth continues in nations like Indonesia and the Philippines, where hundreds of stations collectively support local programming. Unique issues in South Asia, such as station overcrowding, exacerbate co-channel interference, reducing signal clarity in high-density urban and rural zones.^[70]

Advanced and Emerging Technologies

Stereo and Multichannel Systems

Medium wave broadcasting, traditionally monophonic, saw efforts in the late 20th century to introduce stereo audio through compatible analog enhancements that preserved the existing 10 kHz channel bandwidth. The most widely adopted system was C-QUAM (Compatible Quadrature Amplitude Modulation), developed by Motorola and deployed primarily in the United States, Canada, and Japan during the 1980s and 1990s. This phase-modulated variant encodes the sum (L+R) signal via standard amplitude modulation for compatibility, while the difference (L-R) information is carried on a quadrature carrier, all within the allocated bandwidth. A 25 Hz pilot tone is added to the composite signal to activate stereo decoding in compatible receivers, ensuring the system remains backward-compatible with monophonic AM sets through envelope detection.^[71]^[72] C-QUAM achieved channel separation of approximately 20–30 dB across the audio band, providing discernible stereo imaging while minimizing crosstalk in stereo receivers. The Federal Communications Commission endorsed C-QUAM as the U.S. standard in 1993, following years of competing systems that delayed widespread implementation. In practice, the system maintained full compatibility with legacy mono receivers, which simply ignored the quadrature component and reproduced the L+R signal undistorted.^[71]^[72] Attempts to extend medium wave to multichannel audio, such as quadraphonic systems, were limited to experimental broadcasts in the 1970s and proved rare due to bandwidth constraints and complexity. These efforts, often matrix-encoded variants tested on select stations, aimed to deliver four-channel surround sound but lacked standardization and consumer adoption. More recently, iBiquity's HD Radio has incorporated AM stereo capabilities in its hybrid analog-digital framework, where the digital sidebands support stereophonic transmission alongside a monophonic analog host signal, though the overall system relies primarily on digital processing for multichannel features.^[73] Despite technical viability, AM stereo faced significant barriers to adoption, including the scarcity of compatible receivers—peaking at around 100 stations in the U.S. during the 1980s—and heightened vulnerability to interference from atmospheric noise and adjacent channels, which degraded the phase information critical for stereo decoding. These challenges, compounded by the rise of FM stereo and digital alternatives, rendered analog AM stereo largely obsolete in most regions by the early 2000s, with only isolated transmissions persisting today.^[72]

Digital Medium Wave Transmissions

Digital medium wave transmissions represent a shift from analog amplitude modulation (AM) to digital techniques, enabling higher fidelity audio and ancillary data services within the 300 kHz to 3 MHz band. The two principal standards are Digital Radio Mondiale (DRM) and HD Radio. DRM, standardized by the European Telecommunications Standards Institute (ETSI) with specifications from 2001 onward, employs orthogonal frequency-division multiplexing (OFDM) modulation tailored for medium wave, supporting channel bandwidths of 4.5 kHz to 20 kHz to fit existing analog allocations while allowing robust signal propagation over long distances.^[74] In contrast, HD Radio, developed by iBiquity Digital Corporation (now Xperi) and authorized by the U.S. Federal Communications Commission in 2002 with commercial rollout in 2003, operates as an in-band on-channel (IBOC) system that overlays digital signals within the primary analog carrier, preserving backward compatibility for traditional receivers. These standards deliver significant advantages over analog AM, including near-CD-quality audio reproduction and integrated data capabilities. DRM achieves audio bandwidths up to 20 kHz at bitrates up to approximately 35 kbps (Mode A) using advanced audio coding (AAC) or extended high-efficiency AAC (xHE-AAC) codecs, providing clear, noise-free sound suitable for music as well as speech.^[75] HD Radio offers similar stereo audio quality on AM stations, with bitrates up to 40-60 kbps in core modes. Both systems support multimedia data services, such as scrolling text for news or station information via Journaline in DRM, and slideshow images or traffic updates in HD Radio, enhancing listener engagement without additional spectrum.^[76] Robustness against medium wave's multipath fading and interference is enhanced through OFDM's frequency diversity and forward error correction mechanisms, including Reed-Solomon codes in DRM for detecting and repairing transmission errors.^[77] Global implementations vary by region, with DRM seeing broader international adoption outside North America. The British Broadcasting Corporation (BBC) has conducted DRM trials, including medium wave tests in earlier years, to evaluate coverage and receiver performance in urban and rural settings.^[78] India's All India Radio launched DRM services on medium wave in 2017, expanding to 35 operational transmitters as of October 2025, serving vast populations with multilingual programming and reaching more than 900 million people.^[79] In 2024, China adopted DRM as its national digital radio standard for medium wave, with implementation including vehicle receivers starting in 2025. In the United States, HD Radio operates on fewer than 100 AM stations as of 2025, down from peak adoption levels due to limited receiver penetration and competition from digital alternatives, though it persists in some major markets for enhanced audio and subchannels; all-digital AM HD Radio (MA3 mode, without analog carrier) was authorized in 2020 and operates on 4 stations as of 2025.^[80] Despite these benefits, digital medium wave faces practical hurdles that constrain widespread use. Achieving comparable coverage to analog requires higher transmitter power—often 20-50% more—due to the "digital cliff," where signal quality degrades abruptly below a threshold, unlike analog's graceful degradation.^[81] Receiver availability remains low globally, with compatible devices primarily in automotive and specialized markets, hindering mass adoption. As of November 2025, around 50 DRM medium wave services operate worldwide, concentrated in Asia and Europe, but the shift toward internet-based streaming poses risks of phase-out for dedicated digital MW infrastructure in favor of IP delivery.^[82]

Current Challenges and Trends

Interference and Regulatory Issues

Medium wave broadcasting faces significant interference challenges due to its propagation characteristics and shared spectrum environment. Co-channel interference arises primarily from skywave propagation, where signals from distant stations on the same frequency reflect off the ionosphere, leading to clashes especially at night when the ionosphere supports longer-distance propagation.^[83]^[84] This nighttime phenomenon, known as DX interference, can overpower local signals, making reception unreliable over vast areas.^[85] Adjacent-channel interference occurs when signals from nearby frequencies spill over due to inadequate receiver selectivity or excessive transmitter bandwidth, resulting in garbled audio or overlapping programs.^[86] Non-ionospheric sources, such as power lines, introduce broadband noise including a characteristic 50/60 Hz hum from alternating current, which degrades signal quality particularly in areas with overhead lines or faulty equipment.^[87]^[88] To mitigate these issues, broadcasters employ directional antennas to focus radiation patterns and null out unwanted directions, reducing co-channel overlap.^[84] In North America, the Federal Communications Commission mandates power reductions—often to 50% or less—or directional operation at night to limit skywave interference.^[84] Globally, the International Telecommunication Union coordinates frequencies through regional plans, such as the 1970s Geneva Agreement for medium frequency broadcasting, ensuring equitable allocations and minimizing conflicts.^[89] Skywave propagation is predicted using models like Longley-Rice, which account for terrain and ionospheric effects to inform site planning and interference assessments.^[90] Regulatory oversight varies by region but focuses on spectrum protection. In the United States, the FCC enforces interference limits and requires engineering studies for new assignments to prevent harmful overlap in the medium wave band.^[91] The UK's Ofcom regulates medium wave licenses, balancing coverage with interference avoidance through technical conditions on power and antenna patterns.^[92] In India, the Telecom Regulatory Authority (TRAI) oversees analogue medium wave operations, promoting coordination to support public service broadcasting amid growing digital transitions.^[93] Emerging pressures include potential spectrum reallocation near medium wave edges for advanced services like 5G low-band, though direct encroachments remain limited due to band separations.^[94] As of 2025, man-made noise from electric vehicles and solar inverters has intensified urban interference, with EV power electronics generating broadband emissions that blanket the medium wave band, often causing reception blackouts in cities.^[95] Solar photovoltaic inverters contribute similar noise through switching harmonics, exacerbating signal degradation in densely populated areas and prompting calls for stricter emission standards.^[96]

Decline and Future Prospects

The decline of medium wave (MW) broadcasting has accelerated since the 1970s with the widespread adoption of frequency modulation (FM), digital audio broadcasting (DAB), and internet streaming, which offer superior audio quality and flexibility compared to analog AM signals.^[97] In Europe, this shift has led to significant station closures, with more than 20 countries ceasing AM transmissions by 2024 and fewer than 100 MW services remaining active across the continent as of 2025.^[97] In the United States, the number of AM stations has stabilized around 4,300 but reflects an 8% reduction over the past 14 years through 2024, driven by economic pressures and listener migration to digital platforms.^[98] Despite these challenges, MW retains niche roles in emergency broadcasting and underserved regions. In the US, AM stations are integral to the Emergency Alert System (EAS), mandated for participation to disseminate critical alerts during disasters, ensuring reliable one-way communication when power or internet fails.^[99] MW's propagation characteristics continue to support rural and international broadcasting where broadband infrastructure lags, providing coverage in remote areas and penetrating buildings or vehicles more effectively than higher-frequency alternatives.^[50] Hybrid systems combining analog AM with digital overlays, such as Digital Radio Mondiale (DRM), offer a pathway for persistence by enhancing signal robustness without full infrastructure overhauls.^[100] Alternatives have further eroded MW's dominance, with shortwave filling global reach needs through long-distance propagation for international services, and podcasting enabling on-demand audio consumption via apps and streaming without spectrum constraints.^[101] However, low-cost software-defined radio (SDR) receivers have sparked potential revival among enthusiasts, allowing accessible monitoring and decoding of distant MW signals with minimal equipment.^[102] Projections indicate a full phase-out of analog MW in developed nations by the 2030s, as seen in the UK's plans to eliminate AM services while retaining FM until at least 2030 to facilitate digital transitions.^[103] In contrast, growth persists in Africa and Asia, where radio transmitters markets are expanding—Africa's valued at USD 750 million in 2025 and projected to reach USD 1.2 billion by 2031—due to MW's affordability for local and community broadcasting in low-connectivity areas.^[104] As of 2025, trends include ongoing spectrum repurposing in higher bands for emerging uses like IoT, though MW allocations remain primarily for legacy broadcasting in developing regions.^[105]

References

[1]
None
### Definitions and Nomenclature for Radio Frequency Bands
[2]
[PDF] NTIA Report 99-368
This paper discusses the basic aspects of radio-wave propagation and antenna modeling in the medium frequency (MF) band. This band covers the frequencies of.
[3]
Frequency Bands allocated to Terrestrial Broadcasting Services - ITU
Low frequency (LF) and Medium frequency (MF) Bands ; Band [kHz], Region 1, Region 2 ; 148.5-283.5 · NA ; 525-526.5, NA, A ; 526.5-535, A · A ; 535-1605, A · ...Missing: wave | Show results with:wave
[4]
AM Radio | Federal Communications Commission
AM radio stations are known as "mediumwave" stations. They are also sometimes referred to as "standard broadcast stations" because AM was the first form used ...
[5]
The History of the Radio Industry in the United States to 1940 – EH.net
Early radio was driven by inventors, then Marconi dominated, followed by the government-sponsored RCA. The 1930s were the Golden Age of radio.
[6]
None
### Summary of Medium Frequency (MF) Band and Mention of Medium Wave
[7]
Radio Spectrum: ITU Frequency Bands - Electronics Notes
The medium frequency ITU band is far more familiar as it contains the old medium wave broadcast band. The band extends from 300 kHz up to 3 MHz and apart from ...
[8]
Time and Frequency from A to Z, U to W | NIST
The wavelengths of the various frequency bands in the radio spectrum are shown in the table. Wavelength is inversely related to frequency. The higher the ...
[9]
Milestones:Marconi's Early Experiments in Wireless Telegraphy, 1895
Jun 14, 2022 · Marconi's first experiments in wireless telegraphy were aimed at communicating without wires at increasing ranges.Missing: medium | Show results with:medium
[10]
First Wireless Radio Broadcast by Reginald A. Fessenden, 1906
Jun 14, 2022 · On 24 December 1906, the first radio broadcast for entertainment and music was transmitted from Brant Rock, Massachusetts to the general public.
[11]
History of Commercial Radio | Federal Communications Commission
Under the call sign KDKA, Pittsburgh's Westinghouse Electric and Manufacturing Company transmitted the first scheduled broadcast on Nov. 2, 1920. KDKA's Leo ...
[12]
amplitude modulation (am) communication systems
It wasn't until 1906 that amplitude modulation was ready for public demonstration. Fessenden created the first radio broadcast in 1906 and took radio from a ...
[13]
International Radiotelegraph Conference (Washington, 1927) - ITU
The classification of frequencies in two classes was determined and a procedure for notification of frequencies was formulated. Finally, it was decided that the ...Missing: coordination wave
[14]
Radio In The 1930s | History Detectives - PBS
For the radio, the 1930s was a golden age. At the start of the decade 12 million American households owned a radio, and by 1939 this total had exploded to more ...
[15]
Solving the Medium-Wave Problem - Radio World
Oct 10, 2019 · Is medium wave in decline? Some people think so. In the 1950s radio was declared mortally wounded by TV. But then FM with its new music rescued ...
[16]
LF / MF Regional Frequency Assignment Plans - ITU
Plan for MF broadcasting in Regions 1 and 3 and LF broadcasting in Region 1, Geneva, 1975 (GE75). Planning area and frequency bands: , LF: 150-285 kHz. MF: ...Missing: medium | Show results with:medium
[17]
[PDF] FCC ONLINE TABLE OF FREQUENCY ALLOCATIONS
Jul 1, 2022 · 9.3-9.5 GHz, all Regions Reference to 5.475 placed to the right of RADIONAVIGATION. 24.25-24.45 GHz; Region 3 The radio services are listed in ...Missing: medium | Show results with:medium
[18]
[PDF] DIGITAL BROADCASTING SYSTEMS INTENDED FOR AM BANDS
The different channel spacing of LF and MF (9 or 10 kHz) and HF (10 or 5 kHz) lead to differences in the digital modulation procedures, if we require that the ...Missing: rationale | Show results with:rationale
[19]
AM Station Classes, and Clear, Regional, and Local Channels
Jun 3, 2021 · The AM band frequencies are divided into three categories: Clear, Regional, and Local channels. The allowable classes depend on a station's frequency.
[20]
47 CFR § 73.21 - Classes of AM broadcast channels and stations.
The operating power shall not be less than 10 kW nor more than 50 kW. (Also see § 73.25(a)). (2) Class B station. Class B stations are authorized to operate ...
[21]
World Administrative Radio Conference (Geneva, 1979) - ITU
agreement on the expansion of the shortwave spectrum allocated for broadcasting; adoption of major changes in the frequency allocations for the space services.
[22]
https://www.itu.int/en/history/Pages/RadioConferences.aspx?conf=4.101
[23]
[PDF] Radio Waves and the Ionosphere - ARRL
During the day, medium-wave signals propagate only via ground wave because the D layer absorbs signals that reach the ionosphere.
[24]
[PDF] handbook the ionosphere and its effects on radiowave propagation
Sky-wave propagation may be represented by rays reflected between ground and ionosphere. ... DIXON, J.M. [1960] - Some medium frequency sky-wave measurements.
[25]
[PDF] Radio Waves and Communications Distance - ARRL
Lower frequency HF bands have greater ground-wave distance. Higher frequencies have shorter paths. DX contacts are over 1000 miles in high-frequency bands.
[26]
Amplitude Modulation AM Bandwidth Spectrum & Sidebands
Audio bandwidth figures of up to 6 kHz are not uncommon - generally adjacent channels are not allocated so that signals spreading into adjacent channels can be ...
[27]
Understanding Double-Sideband Suppressed-Carrier Modulation
Nov 24, 2024 · In this article, we'll explore an AM variant known as double-sideband suppressed-carrier (DSB-SC) modulation in both the time and frequency domains.
[28]
[PDF] FM Stereo and AM Stereo: Government Standard-Setting vs ... - ERIC
until 1977. From 1977 until 1980, the FCC and NAMSRC conducted testing of the five AM stereo systems and finally selected one system. That tentative ...
[29]
[PDF] AM Antenna Systems - Rockwell Media Services
Directional antennas are used to concentrate signal in some directions. (toward population centers, for instance) while suppressing signal in others (toward.<|control11|><|separator|>
[30]
Kintronic Labs selected by Trans World Radio for Bonaire MW ...
Apr 6, 2016 · Trans World Radio 4-Tower MW Directional Antenna Array on the Island of Bonaire. Kintronic Labs selected by Trans World Radio for Bonaire MW ...
[31]
None
### Summary of Medium Wave Ground Systems, Efficiency, and Soil Losses
[32]
[PDF] UNIT-1 Antenna Basics
Radiation resistance of Short Dipoles and Short Monopoles: The radiation resistance obtained for the current element can be applied to dipoles of short ...
[33]
AM Antenna Tuning Units (ATU's) | Products - LBA Group
... antenna systems to powers in excess of 500 kW. Closely ... Most AM broadcast ATU systems are designed for a single medium wave transmitter frequency.
[34]
Ferrite Rod Antenna - Ferrite Bar Aerial - Electronics Notes
Overview & notes about the ferrite rod antenna or ferrite bar aerial, a form of RF antenna widely used in RFID & portable transistor radio applications.
[35]
[PDF] Analysis and Design of Electrically Small Loop Antennas for LF and ...
This provides magnetic coupling between the receiver's internal ferrite core antenna and the external loop. A theoretical analysis of this configuration is ...
[36]
XHDATA D-808: using an external longwire antenna for MW
Feb 6, 2018 · It is recommended to use 25 metres or more longwire for best results. Obviously, the more longwire used means the lower the frequency gain for ...
[37]
None
### Summary of Receiver Sensitivity and Q Factor from https://fctemis.org/notes/2994_Radio%20Receivers.pdf
[38]
[PDF] LOOP ANTENNAS DESIGN & THEORY - World Radio History
Thus the sensitivity as given by equation ( 7) is limited by Q limitations as a result of bandwidth limitations. For ferrite rod loops, Q limitations are ...
[39]
4- Antennas: To The MW DXer a Beverage Isn't Something You Drink!
Remember that a Beverage has its maximum signal pick-up along its length and that the antenna should point along the great circle path towards the desired ...
[40]
[PDF] The Beverage Antenna, 100 Years Later - ARRL
Traveling-Wave Antennas. The Beverage antenna is a traveling-wave antenna because it never has standing waves from reflections from the ends of the wire. As ...
[41]
[PDF] 4 Fundamental limitations of small antennas
It is commonly understood that as antennas reduce in size, antenna gain and efficiency will degrade and the bandwidth tends to be narrower.
[42]
[PDF] Federal Communications Commission Record
17. The RARC adopted an allotment plan for the ten additional channels (1610~1700 kHz) made available for AM broadcasting in this hemisphere. With few excep- ...
[43]
FCC: 61 AM Stations Lost In 2024 As Religious FM Keeps Surging
Jan 7, 2025 · As of December 31, 2024, there are 4,383 AM stations in the US, a decrease of 17 since Q3 and a total loss of 61 in the calendar year. This ...
[44]
The History of XERF: The Legendary Border Blaster Radio Station
Oct 19, 2014 · XERF was “border blaster” radio station AM 1570 out of Ciudad Acuña, Coahuila, Mexico, across from Del Rio, Texas. The call letters were ...
[45]
Border blasters: The outlaw stations that changed radio
Oct 3, 2024 · In the 1920s, a string of high-powered radio stations on the Mexican side of the Rio Grande changed American culture.
[46]
AM Radio's Role in the Emergency Alert System
AM radio stations continue to function during power outages, natural disasters or other emergencies, providing critical updates and information to the public.
[47]
Congress is trying to force carmakers to keep AM radio - CBS News
Oct 1, 2024 · The radio industry has been fighting back, lobbying for legislation that would force carmakers to install AM radios as a matter of public interest.
[48]
In a Future Filled With Electric Cars, AM Radio May Be Left Behind
Dec 10, 2022 · An increasing number of electric models have dropped AM radio in what broadcasters call a worrisome shift that could spell trouble for the stations.
[49]
Committee approves AM radio requirement for cars - E&E News
Sep 16, 2025 · Legislation requiring cars and trucks, including electric vehicles, to have AM radios easily cleared a House committee Wednesday, although ...
[50]
Broadcasting airtime on AM or Medium Wave (MW) to Europe
Jul 6, 2025 · Because it can reach broad and diverse audiences, AM/Medium Wave is the best choice for talk radio, international broadcasting, public service ...
[51]
Frequency plans - ITU
Regional frequency assignment plans ; GE85-R1-MAR, Planning area: Region 1 ; Maritime mobile, Planned bands: 415 - 495 kHz; 505 - 526.5 kHz; 1 606.5 - 1 625 kHz ...Missing: medium wave<|separator|>
[52]
[PDF] International frequency regulation and planning - EBU tech
One reason for this was that the. Soviet Union had not been invited to the. Washington Conference and was bound only by the Radio Regulations of 1912.
[53]
Radio France: mediumwave and longwave broadcasts to end
Jul 29, 2015 · Radio France, in a cost-cutting measure, will end mediumwave transmissions by the end of this year (2015) and longwave transmissions by the end of 2016.
[54]
Date set for the closure of BBC Radio 4 medium wave frequencies
Mar 21, 2024 · BBC Radio 4 will turn off its medium wave frequencies and end its separate schedule for LW by April 15th 2024.
[55]
MW in Decline as Many Euro Broadcasters Shut Off Transmitters
May 9, 2016 · The closure of European MW stations gained momentum in 2015, when a number of broadcasters silenced their services. “The most famous was ...
[56]
BBC preparing to go online-only over next decade, says director ...
Dec 7, 2022 · The BBC is preparing to shut down its traditional television and radio broadcasts as it becomes an online-only service over the next decade.Missing: medium wave
[57]
Why don't radio stations interfere? | Science Questions
Dec 18, 2012 · As I mentioned earlier, medium wave has about 120 channels available for use across Europe. It's all coordinated internationally so that ...
[58]
DRM+ Digital Radio on FM Band Now Launched in Copenhagen.
Dec 15, 2021 · The frequency allocated is 86.5 MHz and with a bandwidth of 200 kHz, which makes room for two DRM signal. Each DRM signal has a capacity of ...
[59]
Other Countries - Digital Radio Mondiale
DRM was on a medium wave trial a year ago that used to carry a powerful AM signal. The broadcast was on 954kHz (power reported as 3kW) from the České Budějovice ...Missing: DRM+ 2020s transition
[60]
Radio spectrum: the basis of wireless communications
The EU, together with the member states, manages radio spectrum creating the conditions for the development of innovative products and services.Missing: reallocation | Show results with:reallocation
[61]
[PDF] THE EUROPEAN TABLE OF FREQUENCY ALLOCATIONS AND ...
Mar 10, 2023 · A European Table of Frequency Allocations and Applications for the frequency range 8.3 kHz to 3000. GHz (ECA Table) is provided in the ...Missing: 531-1602 | Show results with:531-1602
[62]
[DOC] RNZ-ABU Technical Investigations on DRM in Medium Wave Band ...
Channel width and spacing in ITU-R Region 3 (Asia-Pacific). This region has 18 kHz wide channels following a 9 kHz channel raster, depicted below. Channel 1.
[63]
Map of radio stations in East Asia
Currently there are 880 AM and 1100 FM radio stations in Japan. The FM broadcast band in Japan uses frequencies from 76.0 to 90.0 MHz, in 2014 this band was ...Missing: range | Show results with:range
[64]
1250-1277 kHz: Mediumwave Radio stations in Asia - Asiawaves
Dec 28, 2024 · Language: Chinese. Relays CNR-1: 2230-2300, 1030-1100. Relays Henan Radio and TV Station: 2300-2320.
[65]
[PDF] existing air stations - Prasar Bharati
Mar 19, 2025 · 1. ANANTAPUR. LRS. 10 kW FM. 101.7 MHz MP. 2. CUDDAPAH. RSC. 100 kW MW. 900 kHz TYPE I. 1 kW FM. 103.6 MHz.
[66]
International radio makes new waves | UNESCO
Feb 4, 2020 · RFI has started to open up FM relays outside West African capitals, in the second and third largest cities, and is introducing locally produced ...Missing: infrastructure | Show results with:infrastructure
[67]
Latin American Pirate Radio Stations - HFUnderground
Oct 7, 2022 · There are many pirate radio stations operating in Latin America, although information is sparsely available online.
[68]
Australian A.M. Radio Timelines - Australian Old Time Radio
1978 A.M. radio station frequencies were changed from 10 KHz. spacing to 9 KHz. spacing, creating twelve extra M.W. channels. 1978 2WEB in Burke became the ...
[69]
Radio as an Educational Tool in Developing Countries: Its Evolution ...
Jan 10, 2018 · This paper makes an attempt to trace the evolution and growth of Radio as a tool of education, particularly distance education in the developing countries.
[70]
576-599 kHz : Mediumwave Radio stations in Asia - Asiawaves
All known radio stations in Asia using 576-599 kHz in the mediumwave ( AM ) band · 576 kHz (520.47 metres) Top · 585 kHz (512.46 metres) Top ...
[71]
BTS-1-1 — AM Broadcasting Stereophonic Operation
Mar 12, 2013 · 4 Stereophonic Separation. The separation between the left and right channels shall be at least 20 dB in the frequency range from 400 Hz to ...
[72]
AM Stereo Broadcasting | Federal Communications Commission
Jun 3, 2021 · Stereophonic AM broadcasting in the USA uses the C-Quam system of encoding the stereo signal. This system has been the official standard since 1993.<|control11|><|separator|>
[73]
[PDF] HD Radio™ AM Transmission System Specifications
Mar 13, 2017 · The iBiquity Digital Corporation HD Radio™ system is designed to permit a smooth evolution from current analog amplitude modulation (AM) and ...
[74]
[PDF] ES 201 980 - V4.1.1 - Digital Radio Mondiale (DRM) - ETSI
Medium Wave. NS. North South. OFDM. Orthogonal Frequency Division ... the OFDM modulation with an IFFT the signal path is split according to the ...
[75]
DRM Technology - Digital Radio Mondiale
DRM has excellent sound quality plus the ease-of-use that comes from digital transmissions. The improvement brought by DRM in the AM bands is immediately ...Missing: CD- error correction Reed- Solomon
[76]
DRM Radio: Leading The Way In Global Digital Broadcasting
Aug 16, 2024 · DRM radio can now be used around the world to let you experience high-quality digital audio and information in the form of text and images.Table Of Contents · The Drm Technology · Drm Receivers<|control11|><|separator|>
[77]
[PDF] TS 102 349 - V4.1.2 - Digital Radio Mondiale (DRM) - ETSI
addressing and/or reliable data transmission over error inserting channels using a Reed Solomon (RS) code to provide. Forward Error Correction (FEC) as defined ...
[78]
Digital Radio Mondiale - DRM - BBC
Digital Radio Mondiale is a digital broadcasting system developed originally for the Long- Medium- and Short-wave bands.Missing: 2020s | Show results with:2020s
[79]
https://www.radioworld.com/tech-and-gear/digital-radio/more-than-13m-cars-in-india-will-have-digital-radio-by-end-of-year
[80]
U.S. HD Radio by the Numbers
Sep 22, 2025 · In markets 51–200, this declines by half to 25% penetration. When reached for comment by Radio World, Joe D'Angelo, Xperi's senior vice ...
[81]
The Successful Implementation of High-Performance Digital Radio
Although DRM supports bandwidths of 4.5 kHz, 5 kHz, 9 kHz, 10 kHz, 18 kHz, and 20 kHz within four modes of transmission and reception, bandwidth and bit rate ...
[82]
https://www.drm.org/drm-consortium-position-on-indian-regulators-recommendation/
[83]
[PDF] Development of Techniques to Assess Interference to the MF ...
signals via the skywave mode at night can also lead to interference to local services. This report is devoted to describing the models that have been used.
[84]
Why AM Stations Must Reduce Power, Change Operations, or ...
Dec 11, 2015 · Most AM radio stations are required by the FCC's rules to reduce their power or cease operating at night in order to avoid interference to other AM stations.
[85]
Skywave - Information Station Specialists
This curious effect, which often manifests as nighttime interference, is caused by a phenomenon known as "skywave." Skywave is essentially radio waves from full ...Missing: medium co-
[86]
All digital Medium Wave transmission | Engineering Radio
Nov 20, 2020 · Both systems have 10 and 20 KHz channels available. This could be one feature used to mitigate adjacent channel interference, especially at night.<|separator|>
[87]
Power-Line Noise FAQ - ARRL
It is typically a broad banded type of interference starting at the low end of the radio spectrum. Power-line noise is usually, but not always, stronger on ...Missing: channel
[88]
Mitigation of 50–60 Hz power line interference in geophysical data
Nov 9, 2010 · [6] The electromagnetic interference from power lines, or “hum,” can often be significantly stronger. ... The hum fundamental frequency is 60.0 Hz ...
[89]
Message to the Senate Transmitting the Regional Agreement for the ...
Jun 26, 1987 · The Agreement establishes a Plan of frequency assignments and associated procedures designed to enable the International Telecommunication Union ...
[90]
[PDF] Radio Wave Propagation
Primary Path Loss Prediction. Models. ▫ Longley-Rice Model (MSAM). ▫ TIREM. ▫ CRC-Predict. ▫ Walfish-Bertoni Model. ▫ Walfish-Ikegami Model. ▫ Models Based on.
[91]
Interference Resolution | Federal Communications Commission
Dec 20, 2022 · Investigating and resolving radio frequency interference caused to public safety communications and critical infrastructure.Missing: medium wave
[92]
Rules on using radio equipment - Ofcom
Jul 10, 2023 · The use of radio equipment is regulated by national laws. This page explains the rules that apply, including licence-exempt use and devices like jammers and ...
[93]
[PDF] Recommendations on Formulating a Digital Radio Broadcast Policy ...
Oct 3, 2025 · 1.7 In India, presently the terrestrial radio broadcasting services are available in Medium Wave (MW) and Short Wave (SW) bands. (Amplitude ...
[94]
Understanding Millimeter Wave Spectrum for 5G Networks
Dec 1, 2020 · This spectrum is generally best suited for short range transmissions and can provide a variety of benefits, from coverage extension at the edge ...Missing: encroachment | Show results with:encroachment
[95]
AM Radio in Electric Vehicles: Setting the Record Straight - NAB Blog
Nov 10, 2023 · Techniques and equipment to reduce AM radio interference in electric vehicles add weight to a vehicle, which reduces battery range. Fact ...
[96]
Electromagnetic Interference from Solar Photovoltaic Systems - MDPI
This article presents a review of the important EMC aspects of PVI as a disturbance source. It has the following main parts:
[97]
“Medium wave's sunset in Europe” | The SWLing Post
Jul 17, 2024 · Probably the 9 kHz channel spacing in Region 1 hasn't helped with 10 or 15 kHz bandwidth transmissions. Our system is far from perfect, but ...
[98]
Groups Ponder RIS — “Reductions in Stations” - Radio World
May 27, 2025 · There are still more than 4,300 AM stations in the country. But as of the end of 2024 the total had declined about 8% over the past 14 years, ...
[99]
AM Radio Bill Now Supported by 61 Senators, 280 Representatives ...
Sep 3, 2025 · The AM Radio for Every Vehicle Act is led by Sens. Ted Cruz (TX) and Ed Markey (MA) and Reps. Gus Bilirakis (FL-12) and Frank Pallone (NJ-6).Missing: EAS | Show results with:EAS
[100]
DRM Emphasizes Flexibility and Quality of Service - Radio World
Aug 19, 2024 · AIR has adopted nationwide digital radio services in the medium-wave and shortwave bands using the DRM standard; it has 41 high-power DRM medium ...
[101]
African Broadcasters: Radio Still Reigns Supreme Across Continent
Aug 9, 2023 · No more than 600 million of the continent's more than 1.3 billion people have access to the internet, African broadcasters say.Missing: growth | Show results with:growth
[102]
Medium wave SDR spectrum with over 20 transatlantic signals
Dec 11, 2016 · A review of a MW spectrum with multiple transatlantic signals – all with audio. This is one of the recordings I took with the 200 metre Beverage antenna.Missing: revival | Show results with:revival
[103]
U.K. Review: AM Should Go, FM Stay Until 2030 - Radio World
Oct 25, 2021 · Planning to shut down British AM (MW) radio should begin, while analog FM services should stay on air until at least 2030.Missing: medium wave
[104]
Africa Radio Transmitters Market | Size, Share & Volume 2031
The Africa Radio Transmitters Market was valued at approximately USD 750 million in 2025 and is projected to reach USD 1.2 billion by 2031, growing at a CAGR of ...
[105]
[PDF] Annual Report on the Status of Spectrum Repurposing and Other ...
Most recently, the FCC's C-band auction assigned 280 megahertz of mid-band spectrum, raising $81 billion in revenue in the process.52. Following that was an ...Missing: medium wave