Advanced Qualification · A-005 Transmitters, modulation and processing · A-005-009-011
How does the spread-spectrum technique of frequency hopping work?
- A If interference is detected by the receiver, it will signal the transmitter to change frequency
- B If interference is detected by the receiver, it will signal the transmitter to wait until the frequency is clear
- C A pseudo-random bit stream is used to shift the phase of an RF carrier very rapidly in a particular sequence
- D The frequency of an RF carrier is changed very rapidly according to particular pseudo-random sequence
Correct answer: D — The frequency of an RF carrier is changed very rapidly according to particular pseudo-random sequence. From the official ISED question bank, verified word for word.
Why
Frequency hopping works by making the radio jump its carrier frequency many times per second following a secret, random-looking pattern known as a pseudo-random sequence. The full explanation — and one for every question — is in Pro.
Practise this section
Transmitters, modulation and processing: AM, FM, SSB, keying, speech processing, and the numbers behind occupied bandwidth.