Question

The RF channel in a radio transmitter produces :

• A. Audio signals
• B. Both audio signal and high frequency carrier waves
• C. High frequency carrier waves
• D. Low frequency carrier waves

Answer 1

Answer: (C)

High frequency carrier waves

When audio signals are transmitted over thousands of kilometres through radio transmission, the audio frequencies that lie within the frequency range of 15 Hertz to 20 KiloHertz has very small signal power and thus cannot be transmitted via antenna for communication purposes. The radiation of electrical energy is only possible at frequencies above 20 KiloHertz. Thus, the audio signals must be sent along with the high frequency signals for communication since the high frequency signals can travel long distance without dissipation in power. This can be done by superimposing electrical audio signals on a high frequency wave called the carrier wave by a process called modulation.