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In what stage modulation is done in high power AM transmissions?
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∙ 11y ago
RF Power stage
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∙ 11y ago
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What is the difference between amplitude shift keying and AM modulation system?
Major disadvantage is that telephone lines are very susceptible to variations in transmission quality that can affect amplitude Ann
How does frequency modulation work?
Frequency modulation (FM) works by taking a signal, such as an audio signal, and using it to modulate a higher frequency (Radio Frequency, RF) carrier. This modulation causes the RF to shift up and down in frequency. The RF remains relatively constant in amplitude, and its shifting frequency represents the original signal.Contrast this with Amplitude Modulation (AM) where the RF is relatively constant in frequency, but its amplitude represents the original signal.In order to recover the original signal in an FM system, the receiver must demodulate the signal by measuring the time between successive waves of the RF. In a typical broadcast band system, limitations in the the design requirements for tuning the modulated carrier and for demodulating the original signal force the tuning and demodulation to be done in different stages. Using a process known as superhetrodyning, the tuner amplifies the RF with a broad-band amplifier and mixes the RF with a local oscillator (LO) frequency, converting the RF into an intermediate frequency (IF), typically 10.7 MHz. It then passes the still modulated IF (or shifted RF) into a sharp band-pass filter, the IF stage, and removes the interference of other stations from the IF signal. It then demodulates the original signal from the IF signal.Often, the original signal contains encoded information, such as a stereo subcarrier, which is subsequently demodulated and demultiplexed in order to recover the stereo signal. The question, however, asked about frequency modulation, so the answer stops here. If further detail is required, either add it by refining the answer, or comment on the question, and I or someone will refine the answer.
What is impedance matching?
making impedances identical. when done between supply and load it is done to maximize power transfer. when done on cables and busses it is done to prevent or minimize signal reflections. a low impedance mismatch reflects an inverted signal, a high impedance mismatch reflects an inphase signal.
What is the generation of Single Sideband?
It is the separation of the inverted bands of signals which are formed when an audio signal is mixed with a carrier. This was once thought to be Amplitude Modulation but in fact results in the original carrier plus 2 bands of signals translated from audio to Radio Freq. when they were mixed. They lie on either side of the carrier freq, with the lows adjacent to the carrier and heading away in both directions, LF or HF from carrier frequency to higher tones. For Single Side Band (SSB) use, the carrier is suppressed at generation, as far as is possible, by the use of a balanced modulator in order not to be present in the final signal, in order not to radiate. The side-band chosen for suppression is then attenuated by various methods, modern systems using a crystal filter no wider than the audio band width required for the purpose in hand. It can also be achieved by phasing in the generation stage. Speech is often tailored to as low as 1.8 khz band width, 2.4 khz at the most, for comms. purposes. The advantages of this system over the original double side-band plus carrier, erroneously named AMPLITUDE modulation, are many. Economies of :- Spectrum occupation: Although inverted, both side-bands contain identical information. We really don't need to send it twice in order to reproduce the original sound at the other end. Saves valuable space in the spectrum. Narrow Receive filters will get rid of the next-door neighbours when the system takes advantage and packs more stations into the newly available space. Power: The suppression of the unnecessary side-band reduces the power used and /or the power handling requirements of the device needed to generate the transmitted signal. Alternatively the saved power can be devoted to the wanted side-band, thus increasing the signal at the far end. Similarly, suppressing the carrier will save even higher levels of power, with all the same benefits. The carrier is crucial in the final signal but very easy to re-insert at the receiver end for microscopic amounts of power, ironically in a similar circuit to that which suppressed it in the first. Yet another significant power saving is the removal of the need for a high power audio amplifier used to modulate (mix really) the audio onto the transmitter at very high levels. With the high level "modulation" audio power of 50% of the transmitter power is needed. A 1kW transmitter needs 500 watts of audio whereas done in the early stages of the transmiiter, it needs micro-watts. Outcome: Either lower power consumed or more "talk power" (with the associated increase in signal strength at the far end) for a given amount of power. The original power level had to include 3 sets of signals..Two sidebands, only one of which is needed and an enormous carrier, which isn't needed at all. This shows that it wasn't a carrier after all. How you know that the carrier is on the correct frequency, as you tune your receiver? The other fellow stops sounding like Donald Duck, when you get it right.............easy!
What is the power rating of 500 amperes welding machine?
Welding is done with a high current and low voltage. The voltage of a 500 amp welder might be 10 v so the power rating in that case would be 5000 watts.
In what stage modulation is done on high power amplitude modulation transmission?
In high power AM transmission, modulation is done at
What are the electronic communication?
its nothing but modulation and demodulation. modulation of the message is done in transmitter side and demodulation is done at receiver side and retrieving the original message.
What are the electronic communication process?
its nothing but modulation and demodulation. modulation of the message is done in transmitter side and demodulation is done at receiver side and retrieving the original message.
What is the Digital modulation?
There are 3 main types of digital pulse modulation:Pulse time modulation (PTM), somewhat similar to analog phase modulation.Pulse width modulation (PWM), the width of the pulse represents the signal.Pulse code modulation (PCM), serial transmission of binary bits forming numeric or character codes that represent the signal.All of these can be modulated on an RF carrier using any of the standard modulation techniques: AM, FM, Phase Modulation, etc. One advantage with AM digital pulse modulation techniques over AM analog is that the carrier can be 100% modulated, which cannot be done with analog, thereby allowing significant reductions in transmitter power without loss of coverage range. Sometimes FM digital pulse modulation techniques are referred to as Frequency Shift Keying (FSK). A very complex method of combining Phase Modulation and AM to increase the bit density of digital pulse modulation on an RF carrier is called Quadrature Amplitude Modulation (QAM).
What is the digital pulse modulation?
There are 3 main types of digital pulse modulation:Pulse time modulation (PTM), somewhat similar to analog phase modulation.Pulse width modulation (PWM), the width of the pulse represents the signal.Pulse code modulation (PCM), serial transmission of binary bits forming numeric or character codes that represent the signal.All of these can be modulated on an RF carrier using any of the standard modulation techniques: AM, FM, Phase Modulation, etc. One advantage with AM digital pulse modulation techniques over AM analog is that the carrier can be 100% modulated, which cannot be done with analog, thereby allowing significant reductions in transmitter power without loss of coverage range. Sometimes FM digital pulse modulation techniques are referred to as Frequency Shift Keying (FSK). A very complex method of combining Phase Modulation and AM to increase the bit density of digital pulse modulation on an RF carrier is called Quadrature Amplitude Modulation (QAM).
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 detection of AM?
AM is amplitude modulation. AM detection is the process of demodulation or recovering the information encoded in the signal through amplitude modulation. AM detection can be done through a simple diode detector which rectifies the AM signal.
During what stage of labor is an episiotomy done?
An episiotomy is done during the second stage of labor
How do you do modulation BPSK with a digital input the modulation must use matlab simulink?
BPSK Modulation can be done by using a multiplier. Digital data must be multiplied with the carrier frequency. In matlab simulink use a multiplier block to one input apply a sinusoidal generator & to the other a Pulse generator
Why pre emphasis is done after modulation?
No, Pre-emphasis is done before modulation. We need it to do for improving the SNR ratio of the signals of higher frequencies. Actually this boosting of weaker higher frequencies of data signals. (Asked question is a sort of trap question usually asked in viva or interview.... ;) )
What is AM and FM?
what is AM and FM AM normally refers to Amplitude Modulation while FM refers to Frequency Modulation. As the names suggest, in AM, the carrier wave is modulated by the amplitude of the input signal/waveform while in FM, it is based on the frequency. For further information on how exactly it's done, just run a search for Amplitude Modulation / Frequency Modulation and you should be able to find more detailed information about them.
