Which method is used to counter electronic counter-counter measures by rapidly changing frequencies?

• A. Frequency Hopping
• B. Direct Sequence Spread Spectrum
• C. Time Division Multiplexing
• D. Phase Modulation

Answer: (A)

Rapidly changing frequencies is frequency hopping, a technique designed to defeat jamming by moving the carrier across a range of frequencies in a pseudo-random sequence shared by both ends. Because the signal only dwells briefly on any one frequency, a narrowband jammer has little time to affect it, and a jammer would have to follow the same hopping pattern or blanket a wide portion of the spectrum to be effective. This makes the communication substantially more resilient to electronic countermeasures that target a single frequency. It does require tight synchronization between transmitter and receiver and can demand more bandwidth or face regulatory constraints. Other approaches can help with jamming resistance in different ways, but the defining feature here is using rapid frequency changes to outrun interference.