FCC Exam Question: 6A391
If a 1500 kHz radio wave is modulated by a 2000 Hz sine wave tone, what frequencies does themodulated wave contain?
Explanation: When a radio wave (the carrier) is amplitude modulated (AM) by an audio signal (the modulating tone), the resulting modulated wave contains three primary frequency components: 1. **The original carrier frequency (Fc):** This remains at 1500 kHz. 2. **An upper sideband (USB):** This is the carrier frequency plus the modulating frequency. 2000 Hz is equal to 2 kHz. So, USB = 1500 kHz + 2 kHz = 1502 kHz. 3. **A lower sideband (LSB):** This is the carrier frequency minus the modulating frequency. LSB = 1500 kHz - 2 kHz = 1498 kHz. Therefore, the modulated wave contains frequencies at 1500 kHz, 1502 kHz, and 1498 kHz, making option A correct. Options B and C are incorrect because they use the wrong units (MHz or Hz) for the radio wave frequencies.
6A337
6A582
6A63
6A460
6A243
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Includes Elements 1, 3, 6, 7R, 8, and 9.