Question

Consider an AM broadcast station that transmits modulating frequencies up to 10kHz. If it transmits a frequency of 1000 kHz. Find its maximum and minimum upper and lower sidebands frequencies and also the total bandwidth?

(a) 900 KHz, 820 KHz, 1000 Hz

(b) 720 KHz, 650 KHz, 1020 Hz

(c) 1010 KHz, 880 KHz, 15000 Hz

(d) 1010 KHz, 990 KHz, 20000 Hz

I had been asked this question in exam.

My enquiry is from Coherent Detection of DSBSC Waves topic in portion Double Sideband Suppressed Carrier Modulation of Analog Communications

Answer 1

Right choice is (d) 1010 KHz, 990 KHz, 20000 Hz

For explanation: Maximum Frequency, fm = (1000 + 10) KHz = 1010 KHz.

Minimum Frequency, fl = (1000 – 10) KHz = 990 KHz and,

Bandwidth = 2 * Modulating frequency = Maximum Frequency  –  Minimum Frequency

= (1010 – 990) KHz = 20000 Hz.