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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
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.
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What is square law diode modulator?
Methods of amplitude modulation can be put in the two categories namely Linear modulation methods and Square law modulation methods. Linear modulation method utilizes the linear region of the current voltage characteristics of the amplifying device that is transistor or electron tube. Square law modulation method utilizes the square law region of some current voltage characteristics of a diode or transistor or electron tube. A large number of linear modulation methods have been devised and have been used to varying degree. These methods are namely linear shunt plate modulation or anode choke modulation, linear series plate modulation, grid bias modulation, cathode modulation, suppressor grid modulation, screen grid modulation, collector modulation. Square law modulation circuits make use of non linear current voltage characteristics of diodes or triodes and are in general suited for use at low voltages. Important square law modulation methods are square law diode modulation and balanced modulator.
Why do you use high frequency signals for communication and why not very high frequencies?
Low, medium and high frequencies is ideal for long distance communication but it is very sensitive to QRM and QRN because only amplitude modulation can be used on this part of the RF spectrum, FM modulation is not possible, where in the higher frequencies, FM (Frequency Modulation) is a beter option but with the drawback of distance overland. VHF, UHF and UUHF can't overcome obstacles like hills, mountains and large buildings, only line of site communication can be used here, although it can be used for long distance in open space IE. in outer space, like satellite communication.
How does the circuit of a collector modulation work?
The output stage of the transmitter is a high power frequency class C amplifier. Class C amplifiers conduct for only a portion of the positive half cycle of their input signal. The collector current pulses cause the tuned circuit to oscillate or ring at the desired output frequency. The tuned circuit, therefore, reproduces the negative portion of the carrier signal. The modulator is a linear power amplifier that takes the low level modulating signal and amplifies it to a high power level. The modulating output signal is coupled through modulation transformer T1 to the class C amplifier. The secondary winding of the modulation transformer is connected in series with the collector supply voltage Vcc of the class C amplifier. Read more: [http://www.daenotes.com/electronics/communication-system/am-modulators#ixzz2R69fAPRC http://www.daenotes.com/electronics/communication-system/am-modulators#ixzz2R69fAPRC]
What are the advantages and disadvantages of phase modulation?
Advantage - 1. Phase modulation & demodulation is easy compared to Frequency modulation. 2. Phase modulator is used in determining velocity of moving target by extracting Doppler information. Doppler information needs stable carrier which is possible in phase modulation but not in frequency modulation. Disadvantage - 1. Phase ambiguity comes if we exceed its modulation index pi radian(180 degree). 2. we need frequency multiplier to increase phase modulation index. Visit my website http://harshit.org
Why most of the interrupts in the microprocessor are active low?
If you consider the transistor level of a module, active low means the capacitor in the output terminal gets charged or discharged based on low to high and high to low transition respectively. When it goes from high to low it depends on the pull down resistor that pulls it down and it is relatively easy for the output capacitance to discharge rather than charging. hence people prefer using active low signals.
What is lowlevel amplitude modulation and highlevel amplitude modulation?
low level amplitude modulation occurs when the carrier signal is first modulated and then amplified,whereas in high level modulation,the carrier signal is first amplified and then is modulated.
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.
Does tongue twister help in voice modulation?
it helps the high and the low vocals
Comparison of amplitude modulation and frequency modulation?
Amplitude of the (high frequency) Carrier signal is varied with respect to low frequency of message signal is called amplitude modulation. Frequency of the carrier signal is varied with respect to low frequency of message signal is called frequency modulation.
I am 62 with a testosterone level of 132. How does that compare with normal. What are the consequences of low testosterone?
“I am 62 with a testosterone level of 132. How does that compare with normal. What are the consequences of low testosterone?”
Is cumulus low-level medium-level or high-level?
It is a low-level cloud type.
Why do seamen consider high and low tides in their journey?
They consider high and low tides in their journey because if it is high tide the water level will be high but if it is low tides the water level is low.
Is Cirrostratus low-level medium level or high level?
A high-level cloud type.
How water can travel through drainage?
water always flows from high level to low level. Also in drainage the principle is high level to low level....
Is 34 a low or high level of albumin?
low
Why say that 'c' is high level language?
Well, there are only two categories: low- and high-level languages. Machine code and Assembly are low-level, everything else is high-level.
Amplifiers following the modulated stage in a low level modulation am system be?
linear circuits (class B push pull power amplifier)
