To what does the "4" in FT4 refer?
The correct answer is B: Four-tone continuous-phase frequency shift keying. To what does the '4' in FT4 refer is four-tone continuous-phase frequency shift keying. FT4 uses four tones with continuous-phase FSK. For amateur radio operators, this is important for FT4 operation. Understanding this helps when operating FT4.
Exam Tip
FT4 '4' = four-tone continuous-phase frequency shift keying. Think 'F'T'4' = 'F'our-'T'one 'F'SK. FT4 uses four tones with continuous-phase FSK. Not 4 bits, not 4 cycles per minute - just four-tone FSK.
Memory Aid
"FT4 '4' = four-tone continuous-phase frequency shift keying. Think 'F'T'4' = 'F'our-'T'one. FT4 uses four tones with continuous-phase FSK. Important for FT4 operation."
Real-World Application
FT4 mode: The '4' in FT4 refers to four-tone continuous-phase frequency shift keying. FT4 uses four different tones (frequencies) with continuous-phase frequency shift keying. This is what the '4' means - four-tone continuous-phase FSK.
Key Concepts
Why Other Options Are Wrong
Option A: Incorrect. Multiples of 4 bits of user information isn't what the '4' refers to - it refers to four-tone FSK. Bits isn't the '4'.
Option C: Incorrect. Four transmit/receive cycles per minute isn't what the '4' refers to - it refers to four-tone FSK. Cycles per minute isn't the '4'.
Option D: Incorrect. Since A and C are not correct, 'all of the above' cannot be correct. Only four-tone FSK is correct.
题目解析
The correct answer is B: Four-tone continuous-phase frequency shift keying. To what does the '4' in FT4 refer is four-tone continuous-phase frequency shift keying. FT4 uses four tones with continuous-phase FSK. For amateur radio operators, this is important for FT4 operation. Understanding this helps when operating FT4.
考试技巧
FT4 '4' = four-tone continuous-phase frequency shift keying. Think 'F'T'4' = 'F'our-'T'one 'F'SK. FT4 uses four tones with continuous-phase FSK. Not 4 bits, not 4 cycles per minute - just four-tone FSK.
记忆口诀
FT4 '4' = four-tone continuous-phase frequency shift keying. Think 'F'T'4' = 'F'our-'T'one. FT4 uses four tones with continuous-phase FSK. Important for FT4 operation.
实际应用示例
FT4 mode: The '4' in FT4 refers to four-tone continuous-phase frequency shift keying. FT4 uses four different tones (frequencies) with continuous-phase frequency shift keying. This is what the '4' means - four-tone continuous-phase FSK.
错误选项分析
Option A: Incorrect. Multiples of 4 bits of user information isn't what the '4' refers to - it refers to four-tone FSK. Bits isn't the '4'. Option C: Incorrect. Four transmit/receive cycles per minute isn't what the '4' refers to - it refers to four-tone FSK. Cycles per minute isn't the '4'. Option D: Incorrect. Since A and C are not correct, 'all of the above' cannot be correct. Only four-tone FSK is correct.
知识点
FT4, The '4', Four-tone continuous-phase frequency shift keying, FT4 characteristics
Verified Content
Question from official FCC Extra Class question pool. Explanation reviewed by licensed amateur radio operators.