Deep Dive: E8D03
The correct answer is D: Rapidly varying the frequency of a transmitted signal according to a pseudorandom sequence. Spread spectrum frequency hopping is rapidly varying the frequency of a transmitted signal according to a pseudorandom sequence. The carrier frequency hops from one frequency to another in a pseudorandom pattern. In frequency hopping spread spectrum (FHSS), the transmitter and receiver follow the same pseudorandom frequency-hopping pattern. The signal rapidly jumps between different frequencies according to this pattern. Both transmitter and receiver must be synchronized to the same hopping sequence. FHSS is used in systems like Bluetooth and some military communications. The rapid frequency changes make the signal resistant to interference and difficult to intercept without knowing the hopping pattern.
Why Other Answers Are Wrong
Option A: Incorrect. Frequency hopping doesn't involve the receiver signaling the transmitter to change frequencies. Both follow a predetermined pseudorandom sequence automatically. Option B: Incorrect. Clipping signals to generate harmonics doesn't describe frequency hopping. FHSS changes the carrier frequency, not by generating harmonics. Option C: Incorrect. A binary bit stream shifting phase describes direct sequence spread spectrum, not frequency hopping. FHSS changes frequency, not phase.
Exam Tip
Frequency hopping = Rapidly vary frequency pseudorandomly. Remember: Frequency hopping spread spectrum rapidly varies the frequency of a transmitted signal according to a pseudorandom sequence. The carrier hops between frequencies.
Memory Aid
**F**requency **H**opping = **R**apidly **V**ary **F**requency (think 'FH = RVF')
Real-World Example
You're using a frequency hopping spread spectrum system. Your transmitter rapidly hops between different frequencies (maybe 1000 hops per second) following a pseudorandom pattern. Your receiver follows the same pattern, hopping in sync. An observer without the pattern sees the signal jumping around randomly, making it resistant to interference and difficult to intercept.
Source & Coverage
Question Pool: 2024-2028 Question Pool
Subelement: E8D
Reference: FCC Part 97.3
Key Concepts
Verified Content
Question from the official FCC Extra Class pool. Explanation reviewed by licensed amateur radio operators and mapped to the E8D topic.