just 20 years ago, no AM station of the Federal Capital exceeded the 25 kW peak power, and most passed with 15 kW or a maximum with 20 Kw.
Motivated by the pressure of the ratings and the need for better listen to their stations without interference and without interruption, broadcasters have found the solution to the problem of poor AM reception, was to raise power emissions, to improve the level of field strength throughout the coverage area. So
is like a late 80's began the technological renovation of plants important transmitters of AM and the old valve equipment is gradually replaced with solid-state transmitters last generation, most power of 50 Kw.
This twofold increase in power and evolution of technology was not sufficient because there were reception problems, and then these teams were going to the emergency room and most of the stations were acquired equipment of 100 kW even now there are two 200 Kw transmitters on the market.
As if this were not enough, nearly all plants have been equipped AM management systems, installing masts tuned liabilities, which in most cases gain 3 dB, which means that double the power of its transmitters to the Federal Capital. It seems
, which have increased more than 15 times the power transmission in recent years is not enough, because now questions the excessive distance between transmitter and plants the center of the Federal Capital.
So much so that there are already several major broadcasters are considering moving their plants transmitting, to the very limits of the Federal Capital.
Is this the solution?
no doubt that it will not. Indeed, in my personal opinion, I doubt there is a solution to this problem in the way it raises. Only thorough understanding the strategy that we have erred in the conduct of this business is that we can correct the defect that implies.
Hard with the gradual decline in advertising revenues can cover the depreciation and return on investments made monumental and are making the stations in these projects, more or less acceptable.
The problem has many angles different from which it can analyze, but in this case we're just trying to understand the reception problems AM stations and it is therefore necessary to understand some basics of electromagnetic emissions.
Throughout the world there, and live, radio stations in Amplitude Modulation (AM) and Frequency Modulation (FM) and each has a home market and a different marketing model.
Each modulation scheme has its own characteristics that make it different from the other, and generally are opposed, so that what in a system are strengths are weaknesses in the other and vice versa.
For example, if we analyze the quality of streaming audio, we find that the FM is received with excellent quality, and the AM it does sound quite poor.
If instead we analyze the primary coverage of each system, we see that while the AM covers large areas of several hundred miles with very good reception, an FM station can only cover a few kilometers.
Most reception problems arise when we want to serve big cities, where the average height of buildings is considerable, and where there are countless sources of noise, which hamper the reception of electromagnetic waves, and constitute a radio noise floor, with a threshold so high that sometimes it is impossible to overcome signal stations.
If we add the proliferation of illegal emissions, not just broadcasters, but most radio services covering most of the spectrum, then the city becomes an almost insurmountable barrier to broadcasters.
In this sense, the most affected AM stations, virtually anywhere in the world they intend to supply big cities, but rather they are used, taking advantage of their greater strength, to cover large rural areas are not densely populated, dotted with cities and not too large.
FM stations, for its higher frequency and by the very nature of its system of modulation are less affected by this type of interference, and then become the ideal system to cover urban areas and vehicles on the streets, much more efficient than AM stations, you will find huge amount of points, where his signal virtually disappears.
One of the typical characteristics of PM emissions in large cities, is the loss of uniformity of the signal, which causes a certain point the issue is completely lost, and only moving a few meters to reappear . This phenomenon, sometimes only occurs for a particular frequency, because if we measure in the same spot where a station loses signal, other stations in other frequencies can be tuned without any problem, as their null points occur elsewhere in the city.
This is proved when we make a measurement of field strength, which is neither more nor less than an instrument to measure the amount of signal that is present in a particular place. By measuring at different points in the city, we find that we get very different values \u200b\u200bof field strength, from very good to almost zero, as stated above.
What is remarkable about these measurements is that no connection, or the type of building, or the distance from the transmitting antenna, or any another feature that could be seen with the naked eye. Nor is there a coherent, if we analyze the measurements and confronted with those of other stations on other frequencies, which shows, as noted earlier, that some stations measure good and bad in some other places, and if we move a few blocks , the equation can be reversed.
do you explain this phenomenon?
Obviously the answer is not so visible as a tall building or a nearby power line, we do know that electromagnetic fields affect, particularly when amplitude modulated at low frequencies we speak.
PM emissions, are affected by other issues, whose presence is not as easy to detect but which produce interfering emissions, such as processing chambers underground electrical distribution lines, the gas ballasts for street lighting, traffic lights contactors, the electric ignition systems of cars, motive power systems in buildings, subways, etc.
All these factors and many others, constitute the "noise floor" we mentioned earlier, whose threshold we must overcome our radio signal in order to make it "tunable" by a common receptor radio.
Still, exceeding the noise threshold, many of these interference fields may have components of certain frequencies and phases, which combined with our own sign, or those of other radio stations, to make disappear in one place.
In some cases it has been proven that in a place where the morning was measured by a signal from a station that was almost imperceptible at night significantly improved, because he disappeared interfering factor, which probably is activated only in times labor.
To better understand this phenomenon, we need to see what factors influence the propagation of electromagnetic waves, because in them is the field strength (amount of signal) with which to recepcionar station at a particular point.
For FM stations, like antennas that are used may have a certain gain, which can multiply many times the transmitter power, there is talk of Effective Radiated Power (ERP) which is the power that finally will issue the air, this is the power rating of the transmitter plus antenna gain minus the losses occurring in the cables to reach the antenna.
The second item to come into play, is the average height of the antenna (HMA) that will determine the maximum extent will the station. A higher height, longer range in kilometers.
The last variable is the distance to the transmission plant that is the point of reception, and the obstacles they have to pass the signal to get to that place, like mountains, buildings, etc.
For these reasons, FM stations, try to locate in central areas of the city with very tall towers, antennas of several elements (high gain) and very powerful transmitters. With that obtained more uniform coverage throughout the city, and still manage to get inside homes, buildings and basements, with relative ease. In
AM things are very different, because basically we are talking about frequencies much lower. While in FM are in the order of Megahertz, on AM talk about Kilohertz.
AM To start there is an antenna mounted on a tower and FM, but the very metal of the tower is the radiating element. On AM, the tower is the antenna.
For this reason, the tower should not be as high as possible, as in FM, but must respond to a calculation that depends on the frequency of the station. For optimum efficiency, we say that the tower should have a height equal to half the wavelength, the latter being the inverse of the frequency.
For this reason, low-frequency stations must work with very tall towers, while than the higher frequencies do with lower towers. For example, Continental Radio 590 Khz at an altitude of 250 meters, while American Radio transmitting at 1190 kHz is a tower of 125 meters approximately.
The other issue that should be mentioned on AM antennas, is that unlike the FM, they have no gain, so that the radiated power will be only the rating of the transmitter.
order to obtain gain in AM, in a certain direction, it is necessary to construct an additional mast lower height, called the director, and that at best can double the power in one direction established, but you have in mind that this is not a real gain as that of FM, but it is a power routing, which means that what is gained in that direction, gets lost in the opposite direction. The only thing that changes is the emission diagram.
In these conditions, an AM transmitter plant generates two types of emission, one spatial and one terrestrial. The space issue is not desired, and is spread through the space in which to reach the ionosphere bounces and returns to earth in a remote location far away from the transmitting center. For this reason, some AM stations reported reception reports, especially during night hours, amateur distant countries
The other issue, the land is what interests us, and spreads on the crust, mimicking the topography of the land it crosses. The propagation of these waves, will influence the characteristics of the land, which is called conductivity that will help or hurt the issue.
For example, dry and dusty or desert areas, have low conductivity and hinder the spread, while the wetter areas or the water itself (seas, lakes, etc.) Are better conductivity.
In urban areas, especially those with the highest population density, and thus building, low conductivity at minimum levels and this constitutes an almost insurmountable barrier to the broadcasts.
Another factor is the frequency of the station. The stations of lower frequencies (or longer wavelengths) are greatly favored for which are at the top of the band. Continental, Rivadavia, Radio Mitre 10 and are favored against the spread they have the Red, Belgrano, Splendid, Del Plata, World, and other minor upper band.
Finally the other factor that influences the field strength at a particular point of reception, is the distance that separates us from the transmitter.
sum up, while FM are decisive, effective radiated power (ERP) and antenna height, the AM must take into account: the power of the transmitter, the correct height of the mast and radiating director if any, the distance from the receiver to the plant and conductivity of the ground it traverses.
Each of these issues changed in different proportions, the received signal level at a certain point and to achieve uniform coverage in the service area of \u200b\u200ba station, you must strike a delicate balance of all these variables, only is achieved with a complex engineering design, all equipment and plant facilities and their location transmitter.
Lastly
should take into account operating costs, because when we speak of powers as high as those that are managed at present, the cost of primary energy consumption takes a significant amount that must be taken into account.
All these considerations may help in making decisions, when dealing with issues related to coverage of the station and its relationship with audiences.
Eduardo Daniel Esarey
Motivated by the pressure of the ratings and the need for better listen to their stations without interference and without interruption, broadcasters have found the solution to the problem of poor AM reception, was to raise power emissions, to improve the level of field strength throughout the coverage area. So
is like a late 80's began the technological renovation of plants important transmitters of AM and the old valve equipment is gradually replaced with solid-state transmitters last generation, most power of 50 Kw.
This twofold increase in power and evolution of technology was not sufficient because there were reception problems, and then these teams were going to the emergency room and most of the stations were acquired equipment of 100 kW even now there are two 200 Kw transmitters on the market.
As if this were not enough, nearly all plants have been equipped AM management systems, installing masts tuned liabilities, which in most cases gain 3 dB, which means that double the power of its transmitters to the Federal Capital. It seems
, which have increased more than 15 times the power transmission in recent years is not enough, because now questions the excessive distance between transmitter and plants the center of the Federal Capital.
So much so that there are already several major broadcasters are considering moving their plants transmitting, to the very limits of the Federal Capital.
Is this the solution?
no doubt that it will not. Indeed, in my personal opinion, I doubt there is a solution to this problem in the way it raises. Only thorough understanding the strategy that we have erred in the conduct of this business is that we can correct the defect that implies.
Hard with the gradual decline in advertising revenues can cover the depreciation and return on investments made monumental and are making the stations in these projects, more or less acceptable.
The problem has many angles different from which it can analyze, but in this case we're just trying to understand the reception problems AM stations and it is therefore necessary to understand some basics of electromagnetic emissions.
Throughout the world there, and live, radio stations in Amplitude Modulation (AM) and Frequency Modulation (FM) and each has a home market and a different marketing model.
Each modulation scheme has its own characteristics that make it different from the other, and generally are opposed, so that what in a system are strengths are weaknesses in the other and vice versa.
For example, if we analyze the quality of streaming audio, we find that the FM is received with excellent quality, and the AM it does sound quite poor.
If instead we analyze the primary coverage of each system, we see that while the AM covers large areas of several hundred miles with very good reception, an FM station can only cover a few kilometers.
Most reception problems arise when we want to serve big cities, where the average height of buildings is considerable, and where there are countless sources of noise, which hamper the reception of electromagnetic waves, and constitute a radio noise floor, with a threshold so high that sometimes it is impossible to overcome signal stations.
If we add the proliferation of illegal emissions, not just broadcasters, but most radio services covering most of the spectrum, then the city becomes an almost insurmountable barrier to broadcasters.
In this sense, the most affected AM stations, virtually anywhere in the world they intend to supply big cities, but rather they are used, taking advantage of their greater strength, to cover large rural areas are not densely populated, dotted with cities and not too large.
FM stations, for its higher frequency and by the very nature of its system of modulation are less affected by this type of interference, and then become the ideal system to cover urban areas and vehicles on the streets, much more efficient than AM stations, you will find huge amount of points, where his signal virtually disappears.
One of the typical characteristics of PM emissions in large cities, is the loss of uniformity of the signal, which causes a certain point the issue is completely lost, and only moving a few meters to reappear . This phenomenon, sometimes only occurs for a particular frequency, because if we measure in the same spot where a station loses signal, other stations in other frequencies can be tuned without any problem, as their null points occur elsewhere in the city.
This is proved when we make a measurement of field strength, which is neither more nor less than an instrument to measure the amount of signal that is present in a particular place. By measuring at different points in the city, we find that we get very different values \u200b\u200bof field strength, from very good to almost zero, as stated above.
What is remarkable about these measurements is that no connection, or the type of building, or the distance from the transmitting antenna, or any another feature that could be seen with the naked eye. Nor is there a coherent, if we analyze the measurements and confronted with those of other stations on other frequencies, which shows, as noted earlier, that some stations measure good and bad in some other places, and if we move a few blocks , the equation can be reversed.
do you explain this phenomenon?
Obviously the answer is not so visible as a tall building or a nearby power line, we do know that electromagnetic fields affect, particularly when amplitude modulated at low frequencies we speak.
PM emissions, are affected by other issues, whose presence is not as easy to detect but which produce interfering emissions, such as processing chambers underground electrical distribution lines, the gas ballasts for street lighting, traffic lights contactors, the electric ignition systems of cars, motive power systems in buildings, subways, etc.
All these factors and many others, constitute the "noise floor" we mentioned earlier, whose threshold we must overcome our radio signal in order to make it "tunable" by a common receptor radio.
Still, exceeding the noise threshold, many of these interference fields may have components of certain frequencies and phases, which combined with our own sign, or those of other radio stations, to make disappear in one place.
In some cases it has been proven that in a place where the morning was measured by a signal from a station that was almost imperceptible at night significantly improved, because he disappeared interfering factor, which probably is activated only in times labor.
To better understand this phenomenon, we need to see what factors influence the propagation of electromagnetic waves, because in them is the field strength (amount of signal) with which to recepcionar station at a particular point.
For FM stations, like antennas that are used may have a certain gain, which can multiply many times the transmitter power, there is talk of Effective Radiated Power (ERP) which is the power that finally will issue the air, this is the power rating of the transmitter plus antenna gain minus the losses occurring in the cables to reach the antenna.
The second item to come into play, is the average height of the antenna (HMA) that will determine the maximum extent will the station. A higher height, longer range in kilometers.
The last variable is the distance to the transmission plant that is the point of reception, and the obstacles they have to pass the signal to get to that place, like mountains, buildings, etc.
For these reasons, FM stations, try to locate in central areas of the city with very tall towers, antennas of several elements (high gain) and very powerful transmitters. With that obtained more uniform coverage throughout the city, and still manage to get inside homes, buildings and basements, with relative ease. In
AM things are very different, because basically we are talking about frequencies much lower. While in FM are in the order of Megahertz, on AM talk about Kilohertz.
AM To start there is an antenna mounted on a tower and FM, but the very metal of the tower is the radiating element. On AM, the tower is the antenna.
For this reason, the tower should not be as high as possible, as in FM, but must respond to a calculation that depends on the frequency of the station. For optimum efficiency, we say that the tower should have a height equal to half the wavelength, the latter being the inverse of the frequency.
For this reason, low-frequency stations must work with very tall towers, while than the higher frequencies do with lower towers. For example, Continental Radio 590 Khz at an altitude of 250 meters, while American Radio transmitting at 1190 kHz is a tower of 125 meters approximately.
The other issue that should be mentioned on AM antennas, is that unlike the FM, they have no gain, so that the radiated power will be only the rating of the transmitter.
order to obtain gain in AM, in a certain direction, it is necessary to construct an additional mast lower height, called the director, and that at best can double the power in one direction established, but you have in mind that this is not a real gain as that of FM, but it is a power routing, which means that what is gained in that direction, gets lost in the opposite direction. The only thing that changes is the emission diagram.
In these conditions, an AM transmitter plant generates two types of emission, one spatial and one terrestrial. The space issue is not desired, and is spread through the space in which to reach the ionosphere bounces and returns to earth in a remote location far away from the transmitting center. For this reason, some AM stations reported reception reports, especially during night hours, amateur distant countries
The other issue, the land is what interests us, and spreads on the crust, mimicking the topography of the land it crosses. The propagation of these waves, will influence the characteristics of the land, which is called conductivity that will help or hurt the issue.
For example, dry and dusty or desert areas, have low conductivity and hinder the spread, while the wetter areas or the water itself (seas, lakes, etc.) Are better conductivity.
In urban areas, especially those with the highest population density, and thus building, low conductivity at minimum levels and this constitutes an almost insurmountable barrier to the broadcasts.
Another factor is the frequency of the station. The stations of lower frequencies (or longer wavelengths) are greatly favored for which are at the top of the band. Continental, Rivadavia, Radio Mitre 10 and are favored against the spread they have the Red, Belgrano, Splendid, Del Plata, World, and other minor upper band.
Finally the other factor that influences the field strength at a particular point of reception, is the distance that separates us from the transmitter.
sum up, while FM are decisive, effective radiated power (ERP) and antenna height, the AM must take into account: the power of the transmitter, the correct height of the mast and radiating director if any, the distance from the receiver to the plant and conductivity of the ground it traverses.
Each of these issues changed in different proportions, the received signal level at a certain point and to achieve uniform coverage in the service area of \u200b\u200ba station, you must strike a delicate balance of all these variables, only is achieved with a complex engineering design, all equipment and plant facilities and their location transmitter.
Lastly
should take into account operating costs, because when we speak of powers as high as those that are managed at present, the cost of primary energy consumption takes a significant amount that must be taken into account.
All these considerations may help in making decisions, when dealing with issues related to coverage of the station and its relationship with audiences.
Eduardo Daniel Esarey
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