What is the difference between low level and high level modulation?
The low level transmitter circuit does not require a large AF modulator power so its design is simplified. However the overall efficiency is much lower compared to high level modulation. This is due to the use of less efficient linear amplifiers.
What is high level modulation?
High level modulation occurs when the modulating voltage is applied to the collector/plate circuit of the final power amplifier. With high level modulation, the final stage is operated class C and the preceding stages are also operated class C. The overall efficiency of such a transmitter is very high.
What is meant by low level modulation?
Modulation of a signal at a point in a communications system or device where the power level is low, such as at a distribution frame or a radio microphone, compared with the output power, such as the output power of a long-distance line driver or the output power of a radio transmitter antenna.
What is the difference between low level and high level AM transmitters *?
In high-level transmission, the powers of the carrier and modulating signals are amplified before applying them to the modulator stage, as shown in figure (a). In low-level modulation, the powers of the two input signals of the modulator stage are not amplified.
What do you mean by low level AM?
low-level modulation: Modulation of a signal, e.g., a carrier, at a point in a system or device, such as a radio transmitter, where the power level is low compared to the final output power. (
What is the advantage of low level modulation?
An advantage of low level modulation is that less modulating signal power is required to achieve a high percentage of modulation.
What is the result of over modulation?
Overmodulation results in spurious emissions by the modulated carrier, and distortion of the recovered modulating signal. This means that the envelope of the output waveform is distorted.
What do you understand by the low level AM?
Explanation: In low level AM, modulation is done at low power of carrier and modulating signal therefore output power is low. Therefore, power amplifiers are used to boost the carrier and modulating signal. Collector Modulation Method is high level AM. At high-level AM, output power is high.
Why over-modulation should be avoided?
As you will remember, it is very important to avoid over-modulation. This would distort the amplitude modulated signal and cause undue bandwidth and interference. If over-modulation does occur the carrier is chopped up and the modulation no longer resembles its modulating signal.
How can we prevent over-modulation?
Over-modulation occurs when this maximum level is exceeded, and the result is DISTORTION, or even equipment damage. LIMITERs are used to prevent over-modulation and PEAK CLIPPING.
What do you mean by low level modulation?
Low level modulation is modulating an RF source at a power level of mWs. This has to be increased to the transmission level power by amplifiers, which may have to linear depending on the form of modulation.
What is the block diagram for high level modulation?
The image below is the block diagram of high level amplitude modulation. As this is high level amplitude modulation, therefore it uses a high level AM modulator which operates at high level. Before applying the message signal and the carrier wave to the high-level AM modulator, both of these signals are amplified.
Why do we use a high level AM modulator?
As this is high level amplitude modulation, therefore it uses a high level AM modulator which operates at high level. Before applying the message signal and the carrier wave to the high-level AM modulator, both of these signals are amplified.
How is the wideband used in high level modulation?
The wideband is used to preserve the sidebands of the amplitude modulated wave and then it is transmitted with the help of this antenna. The image below is the block diagram of high level amplitude modulation. As this is high level amplitude modulation, therefore it uses a high level AM modulator which operates at high level.