Subelement G: Transmitters— Topic 53: Oscillators & Modulators
Question 3-53G2
Element 3 (GROL)What is the modulation index of a FM phone transmitter producing a maximum carrier deviation of 6 kHz when modulated with a 2 kHz modulating frequency?
Explanation
The modulation index (m) for a Frequency Modulation (FM) signal is a fundamental parameter that describes the ratio of the maximum carrier frequency deviation to the maximum modulating frequency. It's calculated using the formula:
m = $\Delta$f / fm
Where:
* $\Delta$f (delta f) is the maximum carrier frequency deviation (6 kHz in this case).
* fm is the maximum modulating frequency (2 kHz in this case).
Plugging in the given values:
m = 6 kHz / 2 kHz = 3
Therefore, the modulation index is 3.
Options B and C are incorrect because they represent the deviation and modulating frequency values themselves, not their ratio. Option D is incorrect as it would imply the deviation is equal to the modulating frequency, which is not the case here.
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