Medium wave is the part of the medium frequency radio band used mainly for AM radio broadcasting. The spectrum provides about 120 channels with more limited sound quality than FM stations on the FM broadcast band. During the daytime reception is usually limited to more local stations, though this is dependent on the signal conditions and quality of radio receiver used. Improved signal propagation at night allows the reception of much longer distance signals .
This can cause increased interference, because on most channels multiple transmitters operate simultaneously worldwide. In addition, amplitude modulation is often more prone to interference by various electronic devices, especially power supplies and computers. Strong transmitters cover larger areas than on the FM broadcast band but require more energy and longer antennas. Digital modes are possible but have not reached the momentum yet. FM broadcasting has a high frequency and a small signal coverage, about tens of kilometers, and generally only some local radio stations.
If you use an outdoor antenna, you can receive more, but there are exceptions. Under the influence of a specific time or event , it will also spread far. In the past, there were some FM long-distance receivers and received many foreign radio stations. FM sound quality is better than amplitude modulation, and stereo broadcasting can be achieved, but the threshold effect is significant, and the signal is weak to a certain extent and the signal-to-noise ratio drops sharply.
Medium waves can also reflect off charged particle layers in the ionosphere and return to Earth at much greater distances; this is called the skywave. At night, especially in winter months and at times of low solar activity, the lower ionospheric D layer virtually disappears. When this happens, MW radio waves can easily be received many hundreds or even thousands of miles away as the signal will be reflected by the higher F layer. This can allow very long-distance broadcasting, but can also interfere with distant local stations.
Due to the limited number of available channels in the MW broadcast band, the same frequencies are re-allocated to different broadcasting stations several hundred miles apart. On nights of good skywave propagation, the skywave signals of a distant station may interfere with the signals of local stations on the same frequency. In North America, the North American Regional Broadcasting Agreement sets aside certain channels for nighttime use over extended service areas via skywave by a few specially licensed AM broadcasting stations. These channels are called clear channels, and they are required to broadcast at higher powers of 10 to 50 kW.
Sources of radio waves operate in different frequency bands, and the strength of the electromagnetic field falls rapidly with distance. Over time, a person may absorb more RF energy from a device that emits radio signals near the body than from a powerful source that is farther away. Mobile phones, cordless phones, local wireless networks and anti-theft devices are all sources used in close quarters.
Long-range sources include radio transmission towers and mobile phone base stations. The spectrum provides about 120 channels with limited sound quality. Propagation in the night allows strong signals within a range of about 2,000 km.
What Is The Difference Between Am And Mw Radio Advances in vacuum tube technology (called "valves" in British usage), especially after around 1915, revolutionized radio technology. Vacuum tube devices could be used to amplify electrical currents, which overcame the overheating issues of needing to insert microphones directly in the transmission antenna circuit. Vacuum tube transmitters also provided high-quality AM signals, and could operate on higher transmitting frequencies than alternator and arc transmitters. Vacuum tubes remained the central technology of radio for 40 years, until transistors began to dominate in the late 1950s, and are still used in the highest power broadcast transmitters.
AM radio technology is simpler than later transmission systems. An AM receiver detects amplitude variations in the radio waves at a particular frequency, then amplifies changes in the signal voltage to operate a loudspeaker or earphone. In large urban centres, AM radio signals can be severely disrupted by metal structures and tall buildings. As a result, AM radio tends to do best in areas where FM frequencies are in short supply, or in thinly populated or mountainous areas where FM coverage is poor.
Great care must be taken to avoid mutual interference between stations operating on the same frequency. The daytime map series, in two parts, shows expected groundwave coverage patterns for Unlimited and Daytime , and Critical Hours operations. Daytime signal patterns represent groundwave coverage at two levels, out to the 1.0 and 0.1 millivolts per meter contours. The choice of these levels is made in order to more closely match those which might be helpful to the mediumwave DXer.
Note that daytime reception of signals out beyond the depicted 0.1 mV/m pattern is very possible, and in fact likely for the DXer. The contour line represents a signal strength at the station's extreme fringe distance, a level usually received on a sensitive portable radio with a low ambient local-noise level. I have chosen this signal level to give a good representation of what can be received by most DXers during sunlight hours. With the above said, I tested the radio on shortwave, medium wave and FM and I'm pleased to say that I was delighted by the performance on all bands.
Much has been said on line that medium wave is somewhat deaf with the S-8800 however it hasn't been the case with the unit I've reviewed. Perhaps Tecsun has upgraded the unit from earlier radios in answer to unfavourable reviews of medium wave performance. Of a night, there is a plethora of medium wave stations with 909 khz, China being received easily. Refers to the radio wave frequency called medium wave, also known as intermediate frequency , that is, radio waves with a frequency of 300KHz-3MHz. It can propagate in the form of sky waves reflected by the ionosphere, or it can propagate in the form of ground waves along the surface of the earth.
In the daytime, due to the large absorption of the ionosphere, sky waves cannot be reflected effectively, and mainly rely on ground waves to propagate. However, the ground has stronger absorption of medium waves than long waves, and the diffraction ability of medium waves is worse than that of long waves, so the propagation distance is shorter than that of long waves. For medium-power broadcasting stations, medium waves can travel about 30km. The absorption of the ionosphere decreases at night, which can greatly increase the propagation distance. Unlike telegraph and telephone systems, which used completely different types of equipment, most radio receivers were equally suitable for both radiotelegraph and radiotelephone reception.
In 1903 and 1904 the electrolytic detector and thermionic diode were invented by Reginald Fessenden and John Ambrose Fleming, respectively. Most important, in 1904–1906 the crystal detector, the simplest and cheapest AM detector, was developed by G. Homemade crystal radios spread rapidly during the next 15 years, providing ready audiences for the first radio broadcasts. One limitation of crystals sets was the lack of amplifying the signals, so listeners had to use earphones, and it required the development of vacuum-tube receivers before loudspeakers could be used. The dynamic cone loudspeaker, invented in 1924, greatly improved audio frequency response over the previous horn speakers, allowing music to be reproduced with good fidelity.
AM radio offered the highest sound quality available in a home audio device prior to the introduction of the high-fidelity, long-playing record in the late 1940s. AM broadcasting is radio broadcasting using amplitude modulation transmissions. It was the first method developed for making audio radio transmissions, and is still used worldwide, primarily for medium wave (also known as "AM band") transmissions, but also on the longwave and shortwave radio bands. Most broadcast FM has a channel spacing of 200 kilohertz, with a typical transmission occupying around 150 kilohertz of that.
That is why most FM broadcasts are on high frequencies above 79MHz. You can operate a FM transmitter on the AM bands, using various methods that reduce the bandwidth required, although these severely limit the quality, and require a more complex receiver to decode them. FM has the ability to offer better sound quality, and stereo sound as well, with relatively simple receivers.
To do the same on AM requires more bandwidth than most operators will license, and loses compatibility with the current base of listeners equipment. Hybrid digital broadcast systems, which combine AM transmission with digital sidebands, have started to be used around the world. At night medium wave radio signals can travel much further than during the day. This means your radio is able to receive more radio channels either using the same frequency as the service you are listening to or adjacent to that frequency. The result is a higher level of interference and a deterioration in both the sound and coverage.
Digital radio also provides at least two excellent quality stereo radio channels in the medium wave, using the current state of art xHE-AAC audio codec technologies. This means that, while there was only one analogue radio service possible in each media wave transmitter, with digital radio there are two independent radio services possible. In addition, each of these radio services is in high-quality stereo. In layman's terms, the introduction of digital radio enhances the capacity of the medium wave radio channel fourfold; two- three broadcast channels and one data channel are thus available. The nighttime map series shows expected skywave coverage patterns for Unlimited and Nighttime operations.
Nighttime signal patterns represent the standard SS+6 , 50% signal probability at 0.15 millivolts per meter. Note also that nighttime reception of signals out beyond the depicted pattern is very possible, and in fact quite likely for a skywave signal. The maps represent a signal strength between distant and fringe, a level generally easily received at night on most portable radios. I have chosen this signal level to give a good representation of what should be fairly easily received by most DXers on an average evening.
The nighttime signal probability of 50% means that the signal will be received at this level approximately 50% of the time at Central Standard Time. Because at these frequencies atmospheric noise is far above the receiver signal to noise ratio, inefficient antennas much smaller than a wavelength can be used for receiving. For reception at frequencies below 1.6 MHz, which includes long and medium waves, loop antennas are popular because of their ability to reject locally generated noise. By far the most common antenna for broadcast reception is the ferrite-rod antenna, also known as a loopstick antenna.
The high permeability ferrite core allows it to be compact enough to be enclosed inside the radio's case and still have adequate sensitivity. For weak signal reception or to discriminate between different signals sharing a common frequency directional antennas are used. For best signal-to-noise ratio these are best located outdoors away from sources of electrical interference. Examples of such medium wave antennas include broadband untuned loops, elongated terminated loops, wave antennas (e.g. the Beverage antenna) and the ferrite sleeve loop antenna. The Tecsun S-8800 High-Performance LW/MW/FM/SW Radio is a modern addition to the radio range. Some microbroadcasters, especially those in the United States operating under the FCC's Part 15 rules, and pirate radio operators on mediumwave and shortwave, achieve greater range than possible on the FM band.
On mediumwave these stations often transmit on 1610 kHz to 1710 kHz. Microbroadcasting and pirate radio have generally been supplanted by streaming audio on the Internet, but some schools and hobbyists still use LPAM transmissions. The earliest public radiotelegraph broadcasts were provided as government services, beginning with daily time signals inaugurated on January 1, 1905, by a number of U.S.
In Europe, signals transmitted from a station located on the Eiffel tower were received throughout much of Europe. Radio Umoja FM in the DRC recently launched, aiming to give the community a voice. FM provides a short-range signal - generally to anywhere within sight of the transmitter, with excellent sound quality.
It can typically cover the area of a small city or large town - making it perfect for a radio station focusing on a limited geographical area speaking into local issues. While shortwave and medium-wave stations can be expensive to operate, a license for a community-based FM station is much cheaper. Shortwave (also known as High frequency ) transmissions range from approximately 2.3 to 26.1 MHz, divided into 14 broadcast bands.
Shortwave broadcasts generally use a narrow 5 kHz channel spacing. Shortwave is used by audio services intended to be heard at great distances from the transmitting station. The long range of shortwave broadcasts comes at the expense of lower audio fidelity. Patent 706,737, which he applied for on May 29, 1901, and was issued the next year. Fessenden began his research on audio transmissions while doing developmental work for the United States Weather Service on Cobb Island, Maryland. He later reported that, in the fall of 1900, he successfully transmitted speech over a distance of about 1.6 kilometers , which appears to have been the first successful audio transmission using radio signals.
However, at this time the sound was far too distorted to be commercially practical. For a time he continued working with more sophisticated high-frequency spark transmitters, including versions that used compressed air, which began to take on some of the characteristics of arc-transmitters. Fessenden attempted to sell this form of radiotelephone for point-to-point communication, but was unsuccessful. Shortwave radio uses frequencies in the HF band, from about 1.7 megahertz to 30 megahertz, according to the National Association of Shortwave Broadcasters . Within that range, the shortwave spectrum is divided into several segments, some of which are dedicated to regular broadcasting stations, such as the Voice of America, the British Broadcasting Corp. and the Voice of Russia. Throughout the world, there are hundreds of shortwave stations, according to the NASB.
Shortwave stations can be heard for thousands of miles because the signals bounce off the ionosphere, and rebound back hundreds or thousands of miles from their point of origin. Those changes to a one waveband service were really very welcome at the time. Radio 2 medium wave listeners who listened to it for the music will have been highly annoyed at the changes. But most would have had FM on the same radio it really was a simple switch after all as per Derek Jamieson's demo of way back then showed.
How many people had an MW only radio, or an LW/MW radio but not FM? Most people didn't need to spend a lot of money just to receive radio 2 or radio's 1 and 3 eventually on FM as they already had the equipment to continue to listen to what they had before but in far better sound quality. The implementation of digital radio in the medium wave in Indonesia will offer several substantive advantages. One of these is that medium wave digital radio offers a huge spectrum resource which can be used to mitigate the shortage of frequency spectrum faced by the Indonesian FM broadcasters in Indonesia. This means that many digital radio services can be provided by radio broadcasters in the medium wave, some of these either replacing the crowded FM radio services or putting out new offerings. In the process of propagation, ground waves and sky waves coexist, sometimes causing difficulty in reception, so the propagation distance will not be too far, usually several hundred kilometers.
Mainly used for short-range local radio broadcasting, maritime communication, radio navigation and aircraft communication. The FM broadcast band was established in 1941 in the United States, and at the time some suggested that the AM band would soon be eliminated. Since then the AM band's share of the audience has continued to decline.
In the late 1970s, spurred by the exodus of musical programming to FM stations, the AM radio industry in the United States developed technology for broadcasting in stereo. Other nations adopted AM stereo, most commonly choosing Motorola's C-QUAM, and in 1993 the United States also made the C-QUAM system its standard, after a period allowing four different standards to compete. The selection of a single standard improved acceptance of AM stereo, however overall there was limited adoption of AM stereo worldwide, and interest declined after 1990.
