Deep Dive: E2E04
The correct answer is D: All these choices are correct. Characteristics of the FST4 mode include: four-tone Gaussian frequency shift keying, variable transmit/receive periods, and seven different tone spacings. All three are characteristics of FST4. For amateur radio operators, this is important for FST4 operation. Understanding this helps when operating FST4.
Why Other Answers Are Wrong
Option A: While correct, this is incomplete. Variable periods and tone spacings are also characteristics. Option B: While correct, this is incomplete. Four-tone Gaussian FSK and tone spacings are also characteristics. Option C: While correct, this is incomplete. Four-tone Gaussian FSK and variable periods are also characteristics.
Exam Tip
All three are FST4 characteristics: four-tone Gaussian FSK, variable periods, seven tone spacings. When all listed characteristics apply to FST4 mode, 'all of the above' is usually the answer. All are key FST4 features.
Memory Aid
All three are FST4 characteristics: Four-tone Gaussian FSK, Variable transmit/receive periods, Seven different tone spacings. Think 'A'll 'F'ST4 'C'haracteristics. All three are key features of FST4 mode. Important for FST4 operation.
Real-World Example
FST4 mode characteristics: (1) Four-tone Gaussian frequency shift keying, (2) Variable transmit/receive periods (can be adjusted), (3) Seven different tone spacings (different bandwidth options). All three are characteristics of FST4. This is how FST4 works - all these features are part of FST4.
Source & Coverage
Question Pool: 2024-2028 Question Pool
Subelement: E2E
Reference: 2024-2028 Question Pool · E2 - Operating Procedures
Key Concepts
Verified Content
Question from the official FCC Extra Class pool. Explanation reviewed by licensed amateur radio operators and mapped to the E2E topic.