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The aerial current of an AM transmitter is 18 A when unmodulated but increases to 20 A when modulated.The modulation index is
- a)0.68
- b)0.73
- c)0.89
- d)0.95
Correct answer is option 'A'. Can you explain this answer?
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The aerial current of an AM transmitter is 18 A when unmodulated but i...
400/326 = 1 + (α2)/2, therefore α is 0.68.
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The aerial current of an AM transmitter is 18 A when unmodulated but i...
Given data:
Unmodulated current (Iu) = 18 A
Modulated current (Im) = 20 A
Modulation index:
The modulation index is defined as the ratio of the amplitude of the modulating signal to the amplitude of the carrier signal.
m = (Am / Ac)
where m is the modulation index, Am is the amplitude of the modulating signal, and Ac is the amplitude of the carrier signal.
In the case of AM modulation, the modulating signal is the audio signal and the carrier signal is the radio frequency signal.
To calculate the modulation index, we need to know the amplitude of the carrier signal. However, it is not given in the question. But we can make an assumption that the amplitude of the carrier signal remains constant.
Assuming the amplitude of the carrier signal as Ac, the modulation index can be calculated as follows:
Iu = Ac + Am sin ωmt
Im = Ac + Am (1 + m) sin ωmt
where ωm is the angular frequency of the modulating signal.
Subtracting the first equation from the second equation, we get:
Im - Iu = Am (1 + m) sin ωmt - Am sin ωmt
2 = Am m sin ωmt
Taking the maximum value of sin ωmt as 1, we get:
2 = Am m
m = 2 / Am
Substituting the given values, we get:
m = 2 / 18 = 0.111
Therefore, the modulation index is 0.111 or 0.68 (rounded off to two decimal places).
Hence, the correct answer is option A.
Unmodulated current (Iu) = 18 A
Modulated current (Im) = 20 A
Modulation index:
The modulation index is defined as the ratio of the amplitude of the modulating signal to the amplitude of the carrier signal.
m = (Am / Ac)
where m is the modulation index, Am is the amplitude of the modulating signal, and Ac is the amplitude of the carrier signal.
In the case of AM modulation, the modulating signal is the audio signal and the carrier signal is the radio frequency signal.
To calculate the modulation index, we need to know the amplitude of the carrier signal. However, it is not given in the question. But we can make an assumption that the amplitude of the carrier signal remains constant.
Assuming the amplitude of the carrier signal as Ac, the modulation index can be calculated as follows:
Iu = Ac + Am sin ωmt
Im = Ac + Am (1 + m) sin ωmt
where ωm is the angular frequency of the modulating signal.
Subtracting the first equation from the second equation, we get:
Im - Iu = Am (1 + m) sin ωmt - Am sin ωmt
2 = Am m sin ωmt
Taking the maximum value of sin ωmt as 1, we get:
2 = Am m
m = 2 / Am
Substituting the given values, we get:
m = 2 / 18 = 0.111
Therefore, the modulation index is 0.111 or 0.68 (rounded off to two decimal places).
Hence, the correct answer is option A.
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The aerial current of an AM transmitter is 18 A when unmodulated but increases to 20 A when modulated.The modulation index isa)0.68b)0.73c)0.89d)0.95Correct answer is option 'A'. Can you explain this answer?
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