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In what stage modulation is done on high power amplitude modulation transmission?
Vikashkumar6451
In high power AM transmission, modulation is done at
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How does the intelligence signal modulates the carrier?
There are three major types of modulation:AM, Amplitude Modulation, where the modulation signal is altering the amplitude of the carrier according to its own amplitude, normally this is done in the output stage. Therefor a strong audio signal is necessary at the same or a little less than the power of the carrier, never higher, because that will over modulate the carrier that will resort in distortion of the receiver output. AM is used in the lower band of the RF spectrum.FM, Frequency Modulation, where the frequency of the carrier is altered by the audio signal. When the amplitude of the audio is going higher the frequency go lower. Modulation happen at the oscillator stage, therefor a small audio signal is used to modulate the frequency. FM is normally used in the higher frequency range of the RF spectrum, 50MHz and up.FSK, Frequency-shift keying, used for data transmission, this type of modulation is simply, switching the carrier on and of, a high bit will switch the oscillator on and a low bit will switch it off, in some designs a low will be on and a high off.
What difference between amplitude modulation and double sideband suppressed carrier?
Both are forms of AM but in suppressed carrier a filter is used to attenuate the carrier frequency prior to transmission. This is usually done to reduce the total transmitter power consumption. An ordinary AM radio cannot correctly receive suppressed carrier stations, you must have a receiver that replaces the carrier prior to the detector stage.
What is effect on amplitude shift keying modulation and demodulation due to use of transistor SL100?
The SL100 is a PNP medium power transistor, suitable for use up to ~100MHz. This can be used in the power amplifier stage, with the output connected to a tuning network/transformer + antenna for AM modulation. It's purpose, if used in this application, is to supply current (usually a voltage amplifier circuit will precede this one) to drive the antenna.
What is an amplitude modulation transmitter?
Amplitude Modulation, AM, is a technique where a high frequency carrier of constant amplitude and frequency is modulated by a lower frequency signal. This modulation varies the amplitude of the carrier, and the resultant modulated carrier is what is transmitted. A typical carrier in the standard AM broadcast band is 550 kilohertz to 1.6 megahertz, while the modulating signal is audio, in a range less than 20 kilohertz.Demodulation involves tuning the centerpoint of the carrier and detecting the envelope of modulation, often with a peak follower such as a diode, capacitor and resistor. Very simple AM radios can be built with only a few components, typically with less than six.While there are several demodulation techniques, by for the most common is the superhetrodyne technique. Since selectivity and sensitivity are opposing factors, the RF stage of such a receiver generally trades selectivity for sensitivity, simply boosting the gain with a middle of the road semi-broad band amplifier. Then this is mixed with a local oscillator that is tuned to be exactly 455 kilohertz away from the desired carrier frequency. The mixed signal then is shifted to a center point of 455 kilohertz.This is followed by a very steep skirt band pass filter, the IF stage, which filters out everything but the desired shifted carrier. This is where the selectivity comes in, and since the IF stage is tuned to only one frequency, it can be highly optimized. Actually, the IF stage is three stages, each tuned to slightly different frequencies, so that the response curve, while having steep skirts, and centered at 455 kilohertz, still has the bandwidth necessary to cover the audio range needed.The output of the IF stage is then demodulated using some kind of peak follower, and the output is the original signal.If you analyze the frequency domain of the modulated carrier, you discover that there is a carrier, and two side bands. The carrier contains no information, and consumes about 67% of the total power, while each side band carries the exact same information, but each is backwards to the other.This has led to improvements in design. Sometimes you can suppress the carrier prior to the final amplifier in the transmitter. This gives you the ability to put more power into the side bands. The down side is that the receiver is more complex, and has to regenerate the original carrier and mix it with the suppressed carrier signal before then mixing it for the downshift into the IF stage.You can take this even further, by suppressing both the carrier and one of the sidebands, since all of the signal is contained in both sidebands. Of course, this makes the receiver even more complex.Some CB and Amateur radios are single sideband suppressed carrier, simply known as SSB, in order to boost range. Most broadcast stations are double sideband non-suppressed carrier, simply known as AM, in order to simplify the receiver. Different areas of the world use slightly different terminology, such as SSB-SC, but the intent is the same.
What is the advantage of high level modulation over low level modulation?
Low level modulation: Class B (75%max) power amplifiers are used which offers better quality modulation i.e low distortion probability. Minimize generation of harmonics. The advantage of using a linear RF LP amplifier is that the smaller early stages can be modulated, which only requires a small audio amplifier to drive the modulator. High level modulation: Class C (90%max) power amplifiers are utilized which improves greatly the efficiency of the transmitter but low in quality i.e higher distortion level is expected. A large audio amplifer will be needed for the modulation stage, at least equal to the power of the transmitter output itself. Traditionally the modulation is applied using an audio transformer, and this can be bulky. Direct coupling from the audio amplifier is also possible (known as a cascode arrangement), though this usually requires quite a high DC supply voltage (say 30V or more), which is not suitable for mobile units.
In what stage modulation is done in high power AM transmissions?
RF Power stage
How does the intelligence signal modulates the carrier?
There are three major types of modulation:AM, Amplitude Modulation, where the modulation signal is altering the amplitude of the carrier according to its own amplitude, normally this is done in the output stage. Therefor a strong audio signal is necessary at the same or a little less than the power of the carrier, never higher, because that will over modulate the carrier that will resort in distortion of the receiver output. AM is used in the lower band of the RF spectrum.FM, Frequency Modulation, where the frequency of the carrier is altered by the audio signal. When the amplitude of the audio is going higher the frequency go lower. Modulation happen at the oscillator stage, therefor a small audio signal is used to modulate the frequency. FM is normally used in the higher frequency range of the RF spectrum, 50MHz and up.FSK, Frequency-shift keying, used for data transmission, this type of modulation is simply, switching the carrier on and of, a high bit will switch the oscillator on and a low bit will switch it off, in some designs a low will be on and a high off.
Why frequency modulation is preffered over AM?
-- FM is better for the person on the transmitting end, because it's easier and cheaper to generate with high quality. Modulation can be applied in an early stage of the transmitter, at low frequency, low power, and with a small modulation index, and the final signal for transmission can be derived by frequency multiplication and power amplification, without garfing up (corrupting) the signal and producing a lot of intermod. AM must be modulated at the final frequency and power, which requires half as much audio power as final carrier output power, which is expensive. -- FM is better for the person on the receiving end, because most of the radio noise in nature, as well as man-made radio noise, is amplitude noise. If your receiver doesn't care about changes in amplitude, it's immune to a lot of the noise that gets picked up on the way from the transmitter to the receiver.
What difference between amplitude modulation and double sideband suppressed carrier?
Both are forms of AM but in suppressed carrier a filter is used to attenuate the carrier frequency prior to transmission. This is usually done to reduce the total transmitter power consumption. An ordinary AM radio cannot correctly receive suppressed carrier stations, you must have a receiver that replaces the carrier prior to the detector stage.
Why is AM modulation not an efficient way of modulation?
-- The power output stage in the transmitter must be operated either class A or class B. Whereas in FM the power output stage in the transmitter can operate class C which uses much less power per watt delivered to the antenna. -- For full modulation, audio power is required equal to 1/2 of the RF power of the transmitter output stage. -- At full modulation, 2/3 of the total power arriving at the receiver is at the carrier frequency, which conveys none of the information. -- A receiver designed for AM reception is susceptible to a wide variety of natural and man-made noise.
What is effect on amplitude shift keying modulation and demodulation due to use of transistor SL100?
The SL100 is a PNP medium power transistor, suitable for use up to ~100MHz. This can be used in the power amplifier stage, with the output connected to a tuning network/transformer + antenna for AM modulation. It's purpose, if used in this application, is to supply current (usually a voltage amplifier circuit will precede this one) to drive the antenna.
Amplifiers following the modulated stage in a low level modulation am system be?
linear circuits (class B push pull power amplifier)
What is an amplitude modulation transmitter?
Amplitude Modulation, AM, is a technique where a high frequency carrier of constant amplitude and frequency is modulated by a lower frequency signal. This modulation varies the amplitude of the carrier, and the resultant modulated carrier is what is transmitted. A typical carrier in the standard AM broadcast band is 550 kilohertz to 1.6 megahertz, while the modulating signal is audio, in a range less than 20 kilohertz.Demodulation involves tuning the centerpoint of the carrier and detecting the envelope of modulation, often with a peak follower such as a diode, capacitor and resistor. Very simple AM radios can be built with only a few components, typically with less than six.While there are several demodulation techniques, by for the most common is the superhetrodyne technique. Since selectivity and sensitivity are opposing factors, the RF stage of such a receiver generally trades selectivity for sensitivity, simply boosting the gain with a middle of the road semi-broad band amplifier. Then this is mixed with a local oscillator that is tuned to be exactly 455 kilohertz away from the desired carrier frequency. The mixed signal then is shifted to a center point of 455 kilohertz.This is followed by a very steep skirt band pass filter, the IF stage, which filters out everything but the desired shifted carrier. This is where the selectivity comes in, and since the IF stage is tuned to only one frequency, it can be highly optimized. Actually, the IF stage is three stages, each tuned to slightly different frequencies, so that the response curve, while having steep skirts, and centered at 455 kilohertz, still has the bandwidth necessary to cover the audio range needed.The output of the IF stage is then demodulated using some kind of peak follower, and the output is the original signal.If you analyze the frequency domain of the modulated carrier, you discover that there is a carrier, and two side bands. The carrier contains no information, and consumes about 67% of the total power, while each side band carries the exact same information, but each is backwards to the other.This has led to improvements in design. Sometimes you can suppress the carrier prior to the final amplifier in the transmitter. This gives you the ability to put more power into the side bands. The down side is that the receiver is more complex, and has to regenerate the original carrier and mix it with the suppressed carrier signal before then mixing it for the downshift into the IF stage.You can take this even further, by suppressing both the carrier and one of the sidebands, since all of the signal is contained in both sidebands. Of course, this makes the receiver even more complex.Some CB and Amateur radios are single sideband suppressed carrier, simply known as SSB, in order to boost range. Most broadcast stations are double sideband non-suppressed carrier, simply known as AM, in order to simplify the receiver. Different areas of the world use slightly different terminology, such as SSB-SC, but the intent is the same.
What is low level AM modulator?
Historically, AM modulation has always been applied to the final power amplifier stage of the transmitter, just before it goes to the antenna. The reason for doing it this way is that once it's modulated, the composite signal can't be handled by any non-linear devices; any non-linearity generates new frequencies, which would have the effect of introducing audible distortion into the modulated signal.The disadvantage of AM-modulating the final amplifier stage is that doing so requires audio power equal to 50% of the carrier power ... if you're running a 50 KW AM radio station, you need 25 KW ( ! ) of clean audio to modulate it with. You know what 100 watts of audio for your Home Theater or your car costs, so you can imagine what 25 KW of broadcast-quality audio, or even 5 KW, must cost.Low level modulation means modulation applied to a low-power stage before the power amplifier boosts it to the full transmit power level. That's obviously a great benefit, because you don't need nearly as much audio power, so the audio stages are much less expensive. BUT ... it means that every stage after modulation must be a highly linear stage, in order to avoid distortion. So now, instead of a husky Class-C final power amplifier, it has to be a Class-A (I think maybe Class-AB also works). Class-A for a final means much lower efficiency, so it has to be bigger, and use more DC power supply than the old Class-C needed, in order to send the same power up to the antenna. So it's a cost trade-off.
Compare high level modulation and low level modulation?
IN LOW LEVEL MODULATION THE MODULATING SIGNAL IS APPLIED NEARER THE CARRIER OSCILLATOR N IN HGH LEVEL MODULATION MODULATING SIGNAL IS APPLIED AT OUTPUT OF FINAL POWER AMPLIFIER OR FAR FROM CARRIER OSCILLATOR... IN OTHER WORDS :::: IN HAIGH LEVEL MODULATION THE AF SIGNAL IS APPLIED TO COLLECTOR OR PLATE AS THEIR RESPECTIVE DEVICES..... N IN LOW LEVEL MODULATION AF SIGNAL IS APPLIED AT BASE OR GRID IN TRANSISTOR AND TUBES RESPECTIVILY IN LOW LEVEL MODULATION THE MODULATING SIGNAL IS APPLIED NEARER THE CARRIER OSCILLATOR N IN HGH LEVEL MODULATION MODULATING SIGNAL IS APPLIED AT OUTPUT OF FINAL POWER AMPLIFIER OR FAR FROM CARRIER OSCILLATOR... IN OTHER WORDS :::: IN HAIGH LEVEL MODULATION THE AF SIGNAL IS APPLIED TO COLLECTOR OR PLATE AS THEIR RESPECTIVE DEVICES..... N IN LOW LEVEL MODULATION AF SIGNAL IS APPLIED AT BASE OR GRID IN TRANSISTOR AND TUBES RESPECTIVILY
Which consumes high power between FM and AM radio system?
-- For the same amount of radiated RF power, AM transmitters use more primary (utility) power, because the modulation must be applied to the final output stage, requiring high audio power. -- Commercial FM stations will typically radiate more RF power than AM stations, because of the relatively higher free space attenuation at the higher frequency of the commercial FM band ... they need more power to cover the same size 'market' area. But that's the result of their spot on the radio dial, not their modulation technique.
What is the advantage of high level modulation over low level modulation?
Low level modulation: Class B (75%max) power amplifiers are used which offers better quality modulation i.e low distortion probability. Minimize generation of harmonics. The advantage of using a linear RF LP amplifier is that the smaller early stages can be modulated, which only requires a small audio amplifier to drive the modulator. High level modulation: Class C (90%max) power amplifiers are utilized which improves greatly the efficiency of the transmitter but low in quality i.e higher distortion level is expected. A large audio amplifer will be needed for the modulation stage, at least equal to the power of the transmitter output itself. Traditionally the modulation is applied using an audio transformer, and this can be bulky. Direct coupling from the audio amplifier is also possible (known as a cascode arrangement), though this usually requires quite a high DC supply voltage (say 30V or more), which is not suitable for mobile units.
