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Transcripts for Mann DX, Page Four |
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Carl Mann DX: Carl Mann of Omaha, Nebraska is a veteran journalist and radio hobbyist. Carl has been introducing KNLS listeners to the world of distance listening (DXing) for more than a decade. You can review Carl's scripts by clicking on the subjects listed above.
Zero Beat tuning, also called ECSS tuning, is a method used by Dxers to increase the readability of a poor AM signal. It requires the use of the receiver’s single sideband mode or beat frequency oscillator, also called the BFO. It’s the same as tuning in an AM station like it was a single sideband transmission. Some Dxers prefer using the Sideband mode or the BFO while tuning across a band. Each station creates a tone sweeping from one end of the scale to the other as the receiver tunes by, even on stations too weak to produce audio. Zero beat tuning is accomplished by carefully tuning in on the center of a station so that the tone goes down in scale, stopping just at the point where the tone disappears. This point is called the zero beat. At this point the station’s audio will become intelligible once again. In some cases this tuning method will improve the readability of the station. In sideband most receivers are using their most narrow bandwidth filters for increased selectivity. Fading and flutter is reduced because the receiver is placing its own steady carrier wave over that of the station. And the heterodyne note produced by a pair of stations too close together can be eliminated by properly zero beating on the desired station. Zero beating also allows measurement of the station’s frequency with the greatest accuracy because the zero beat is on the exact center frequency of the station. On the minus side, music cannot be enjoyed in its full range this way.
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Pirates are unlicensed stations that sneak on the air with brief broadcasts then disappear before there’s a chance for them to be tracked down. In some countries where the laws may be more relaxed or confusing, pirates may operate in the open as regular stations. They most commonly operate in America and Europe. Pirate broadcasting likely got its name from unlicensed stations operating from aboard ships in international waters. Also called Offshore Radio, some of these stations in the North Sea were quite successful in the 1960s, offering entertainment and pop music not found on local government networks like the BBC. From Radio Caroline in the 1960s to Laser Radio in the 1980s, the stations came and went, finally choked off the air when governments in the target countries made it illegal for land-based businesses to support them. In the U.S., the typical pirate operator is a radio hobbyist with a strong desire to become a broadcaster. Often an advocate for Free Radio, he argues for the right to broadcast without having to go through the long, expensive, and sometimes futile process of getting a license. The government’s position is to seek out and silence pirates because they can interfere with legal stations. American pirates typically broadcast for less than an hour, giving only a name or slogan for identification, most often heard on weekends and holidays. Programming usually consists of whatever the operator finds interesting: off beat music, sound effects, or silly narration. Pirates make interesting and challenging DX targets. Some QSL using a third party address. The preferred frequency of the 1990s is on or near 6955 kHz. It should be noted that Pirate stations differ from clandestine stations, which also operate in secrecy but operate for political reasons.
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Radio signals traveling great distances are subjected to varying ionospheric conditions that create a form of interference called fading. Slow fades on shortwave are most frequent when the ionosphere is strengthening or weakening causing a station to fade in and out. Some slow fades happening at times where conditions change between day and night are long lasting rather than going in and out. There are other kinds of fading to describe the reception a signal. Random fading is the wavering of a signal that is otherwise at a consistent strength. This happens because the ionosphere is not a smooth refractor of radio waves. It distorts and scatters the signal on each skip. The flutter fade sounds like the signal is almost vibrating. It’s most common on signals traveling polar routes, particularly during times of high sunspot activity. Selective fading will sometimes be noticed on stronger stations of medium distance from the listener. It happens when the station’s signals arrive by two different paths. As the signal taking the longer path begins to take over, it cancels out the signal arriving by the shorter path, causing a fade out. But the sidebands, the part of the signal that carries the sound, remain strong. Without the carrier signal, sound becomes distorted. This usually lasts just a minute or so. There are ways to reduce fading at the reception point, but it requires large antenna fields. Experimenters find that at any given instant a signal will be at different strengths at different points in the reception field. So, by creating antenna systems large enough to cover the field, the signals received will combine and average out to become steadier. This is not practical for the average listener but may be found in military and commercial communication.
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The dial position of a radio station can be described in frequency or wavelength. The frequency is measured in hertz, or cycles per second. The wavelength is measured in meters.
A wavelength is the distance between each radio wave leaving a transmitter antenna at a given frequency. Each radio wave radiates outward from the antenna traveling at the speed of light. At that fixed speed, the wave travels only a short distance before the next wave is radiated. The distance between the waves, measured in meters, is the wavelength. At higher frequencies, where even more radio waves are transmitted each second, there is less distance between the waves. The wavelengths become shorter.
For example, a shortwave station broadcasting on 10 megahertz will be radiating 10 million radio waves each second. At the speed of light, a wave on this frequency will travel only 30 meters before the next radio wave leaves the antenna. The wavelength for WWV on 10 mHz is 30 meters. WWV on 15 mHz is on the wavelength of 20 meters, because the frequency is higher and the radio waves are transmitting more frequently allowing less space between each as they leave the antenna. The formula to determine wavelength is: 300 divided by the frequency in mHz.
When radio was developed in the early 1900’s a station’s wavelength was always given rather than frequency. The switch to cycles, later called Hertz, came in the 1920’s, but it took another 10 years before listeners accepted the change. On shortwave, wavelength is still used to describe bands of frequencies. For example the 49 meter band is the portion just above 6 mHz, and the 31 meter band is just below 10 mHz.
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Shortwave, and radio in general, developed first as a communication tool. It was called wireless and immediately was put to use in ship to shore communication. Communication stations of all types followed: International telephone, marine and air navigation and two-way stations, military and amateur radio operator communication, program relays and facsimile and radio teletype stations. Facsimile is the transmission of still pictures to special devices connected to the receiver. Radio teletype, also abbreviated RTTY, is the transmission of text which will be typed out or displayed on a computer screen at the reception point. These stations are all utility stations. Some utility stations broadcast one-way transmissions. That would include Coast Guard stations issuing weather reports, standard time and frequency stations like WWV in the U.S and JJY in Tokyo, and some news agencies operating radio teletype or facsimile stations. Utility DX provides a unique set of challenges. The transmitters are relatively low power, particularly those in mobile operation. They can be more difficult to identify without up to date listings, they often operate erratically on an as-needed basis, and in the case of ships and aircraft are heard by chance depending on their locations. Also the Dxer must be able to tune single sideband for voice transmissions and understand Morse code for others. And special equipment is needed to copy some transmissions, such as radio teletype and facsimile. The face of Utility DX is always changing. Satellites, digital transmission and computers are taking over many two-way, radio teletype and facsimile circuits. Gone are the overseas telephone transmitters that once transmitted their markers between conversations. Also gone is the use of morse code by the U.S. Coast Guard, discontinued in 1995 after over 80 years of use. Some utility stations verify reception reports with their own QSL cards. There are clubs and magazine sections devoted to the utility Dxer.
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In the dawning days of broadcasting the only way a station could tell if it was being heard was by listener response. Stations would request letters or run mail-in contests promising a prize or a small gift in return to see how many listeners they might have. This was important for sponsors and for the engineering staff. Most often stations would reply with a QSL card verifying the reception like ham radio operators do. QSL card collecting started and continues today. A listener’s letter to the station for a QSL card is the reception report. Today, most large broadcasters already know how they are “getting out,” frequently using computer propagation forecasts and employing monitors in the target areas. Regional stations don’t often care that they can be heard beyond their own area. But some stations still find a reception report useful, and most like to hear from listeners anyway. A proper reception report details a specific reception period. It starts with the date, time, and frequency of the reception, then describes the signal’s strength, describes any interference and its source, and includes some program details to prove the correct station was monitored. The report portion of the letter then concludes with a description of the receiver and antenna being used. Continue your letter with some information about yourself and your hometown, and offer some comments on the station’s programming. Then be sure to politely request a QSL card in reply. Sending return postage for the reply is always necessary except for most international broadcasters. Since your own country’s stamps cannot be used in another country, Dxers can either find a source for international postage stamps, buy International Reply Coupons at their local post office, or send some form of currency. This can add up to quite an expense.
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A QSL is a written card or letter verifying that a station was heard at a particular time and date on a specific frequency. Listeners and Dxers who offer an accurate report of a specific reception obtain it from stations. The practice began with amateur radio operators who would verify each others radio contact by mail, offering written proof of the contact for years to come. Collecting QSL cards quickly became popular. The practice was taken up by broadcasters as a means of enticing listeners to write in. Mail response was important to determine listenership and the station’s signal quality. The term QSL comes from the Amateur Radio Operator’s Q-code. In using morse code, it’s easier to send three letter combinations for some more commonly used words. For example, QTH means location, QRM means interference, and QRN is static. QSL means verification of the contact by mail. Though not all shortwave listeners get involved in QSL collecting, to some building a collection of cards from all over the world is a challenge equal to chasing down rare DX. Cards from stations rarely heard or no longer on the air become treasures in the collection. To the more casual listener, a collection may only include a grouping of favorite stations. Some stations change their QSL card design regularly, to provide a variety for the listener who writes frequently. While the major International broadcasters still offer QSL cards, most other stations have a much lesser interest in hearing from distant listeners outside their primary target area. They may QSL only as a courtesy to hobbyists. Some only sporadically reply; others may not at all. This provides a challenge for the serious QSL card collector, who is known to go to great lengths to get a reply from a station.
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Radio waves travel outward from the transmitting antenna in all directions. The part that goes skyward is called the skywave. The signal that travels along the ground is the groundwave. Groundwave is useful for local broadcasting because it’s consistent and reliable, but it only reaches out a limited distance. Skywave radiates upward, much of it going out into space to be lost forever. But on shortwave frequencies the ionosphere can affect these signals. The ionosphere can refract the signals so that they bend back down toward the earth to be heard hundreds of miles away, far beyond the reach of that transmitter’s groundwave. Just how far skywave can reach around the world depends on the intensity of the ionosphere at the time, the angle of the skywave takeoff from the transmitter, and the frequency of the signal. Often it requires multiple hops for a skywave to reach great distances, the signal bouncing back upward from the earth for another reflection from the ionosphere. As a station’s frequency becomes higher, the groundwave reach lessens while the skywave intensity increases. The area between the limit of the groundwave and the first return of the skywave from the ionosphere is called the skip zone. However some signal may weakly return from the ionosphere back into the skip zone under conditions called back scatter. There is a limit where the higher frequencies are no longer refracted downward. This is called the maximum usable frequency, or MUF. The skywave signal instead will penetrate the ionosphere and travel on into space. The MUF constantly varies according to ionospheric conditions, usually going up to around 18 to 22 mHz during the day, but it has been known to go beyond 50 mHz under unusual conditions.
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To propagate is to spread. In the case of radio propagation, it is the spreading of radio waves, and how they travel such great distances. Although this could include the directional patterns of antennas, in shortwave it’s is primarily the study of the solar effects upon the ionosphere. Solar means: derived from or relating to the sun. Understanding propagation is important in making the best use of the shortwave bands. The ionosphere was discovered early in the days of radio when signals on mediumwave and low frequencies were being used and sometimes heard at great distances during the night. It turned out that a layer of electrically charged particles circling the earth refracts radio waves back down far beyond the horizon. Originally called the heaviside layer, named after the man who discovered it, the ionosphere was later discovered to perform more efficiently at higher frequencies, those being shortwave, going farther with less transmitter power. The electrical qualities of the ionosphere vary widely. It’s affected by being exposed to sunlight, so a frequency that works during the day may not necessarily work at night. It’s also affected by solar radiation, which increases as the number of sunspots on the sun’s surface increase. These high sunspot counts peak about every 11 years, the average solar cycle. And lastly the ionosphere is affected by solar storms that suddenly occur during high sunspot counts and disrupt the ionosphere blacking out long distance shortwave completely. Propagation forecasting is built on the sunspot count and the observance of solar flares in order to determine shortwave conditions. The forecasts are made available through government agencies. In the U.S. they are broadcast hourly on WWV and WWVH.
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In music a harmonic is a musical overtone in harmony with the first. In radio it is the multiple of any given transmitter frequency. Transmitters are capable of putting out signals on their harmonic frequencies as well as on their primary frequency. As an example, a station on 3.3 mHz could put out a second harmonic on 6.6 mHz, a third harmonic on 9.9 mHz, and so on up the spectrum. Each successive harmonic is weaker than the last. Harmonics are not welcome and in fact are not legal; they create interference. Well-tuned and properly maintained transmitters don’t put out harmonics. Also filters will suppress harmonics at the transmitter’s output. Still, if a listener is not too far away from a high power station it is not uncommon to weakly hear some of that station’s harmonics. Dxers will sometimes hear harmonics of medium wave stations appearing in the 2 to 3 mHz range. This allows some stations to be heard where their primary frequency might not propagate well or be blocked by other stations. More detective work is required to identify a harmonic, having first to compute the possible primary frequencies, then to investigate the listings. For example, a strange signal being heard on 2.4 mHz could be the second harmonic of 12 hundred kilohertz, or the third harmonic of 6 hundred kiloHertz, both primary frequencies being on the mediumwave band. Getting a QSL card from a station heard on its harmonic is rare as few will admit they can be heard on an illegal frequency. Harmonics don’t just go upward from the primary frequency, but can go downward, though this happens less often. Harmonics that are divisions of the primary frequency are called sub-harmonics.
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The New Life Station is pleased to provide transcripts online for a number of KNLS programs. Please note that all scripts are the property of World Christian Broadcasting and/or SeedSower Productions. They are provided here for your personal enjoyment only and may not be disseminated in any fashion without prior written permission.