What technique minimizes the bandwidth of a PSK31 signal?
The correct answer is C: Use of sinusoidal data pulses. The technique that minimizes the bandwidth of a PSK31 signal is the use of sinusoidal data pulses. PSK31 uses smooth, sinusoidal-shaped pulses instead of rectangular pulses, which reduces bandwidth.
Rectangular pulses have sharp edges that create wide spectral sidebands. Sinusoidal pulses have smooth transitions that concentrate energy in a narrower bandwidth. PSK31's use of sinusoidal data pulses, combined with phase changes at zero crossings, keeps the signal bandwidth very narrow (about 31 Hz). This is why PSK31 can operate in such a narrow bandwidth - the smooth pulse shape minimizes spectral spreading. This is a key design feature that makes PSK31 bandwidth-efficient.
Exam Tip
PSK31 bandwidth minimization = Sinusoidal pulses. Remember: PSK31 minimizes bandwidth by using sinusoidal data pulses instead of rectangular pulses. The smooth pulse shape reduces spectral spreading.
Memory Aid
"**P**SK31 **B**andwidth = **S**inusoidal **P**ulses (think 'PB = SP')"
Real-World Application
You're operating PSK31, which uses sinusoidal data pulses. Instead of sharp rectangular pulses that would create wide sidebands, PSK31 uses smooth, sine-wave-shaped pulses. This keeps the signal bandwidth very narrow (about 31 Hz), allowing many PSK31 signals to fit in a small frequency range without interference.
FCC Part 97.3Key Concepts
Why Other Options Are Wrong
Option A: Incorrect. Zero-sum character encoding isn't a technique for minimizing bandwidth. PSK31 uses Varicode, not zero-sum encoding.
Option B: Incorrect. Reed-Solomon encoding is for error correction, not bandwidth minimization. PSK31 doesn't use Reed-Solomon encoding.
Option D: Incorrect. Linear (rectangular) data pulses would actually increase bandwidth due to sharp edges. Sinusoidal pulses minimize bandwidth.
题目解析
The correct answer is C: Use of sinusoidal data pulses. The technique that minimizes the bandwidth of a PSK31 signal is the use of sinusoidal data pulses. PSK31 uses smooth, sinusoidal-shaped pulses instead of rectangular pulses, which reduces bandwidth. Rectangular pulses have sharp edges that create wide spectral sidebands. Sinusoidal pulses have smooth transitions that concentrate energy in a narrower bandwidth. PSK31's use of sinusoidal data pulses, combined with phase changes at zero crossings, keeps the signal bandwidth very narrow (about 31 Hz). This is why PSK31 can operate in such a narrow bandwidth - the smooth pulse shape minimizes spectral spreading. This is a key design feature that makes PSK31 bandwidth-efficient.
考试技巧
PSK31 bandwidth minimization = Sinusoidal pulses. Remember: PSK31 minimizes bandwidth by using sinusoidal data pulses instead of rectangular pulses. The smooth pulse shape reduces spectral spreading.
记忆口诀
**P**SK31 **B**andwidth = **S**inusoidal **P**ulses (think 'PB = SP')
实际应用示例
You're operating PSK31, which uses sinusoidal data pulses. Instead of sharp rectangular pulses that would create wide sidebands, PSK31 uses smooth, sine-wave-shaped pulses. This keeps the signal bandwidth very narrow (about 31 Hz), allowing many PSK31 signals to fit in a small frequency range without interference.
错误选项分析
Option A: Incorrect. Zero-sum character encoding isn't a technique for minimizing bandwidth. PSK31 uses Varicode, not zero-sum encoding. Option B: Incorrect. Reed-Solomon encoding is for error correction, not bandwidth minimization. PSK31 doesn't use Reed-Solomon encoding. Option D: Incorrect. Linear (rectangular) data pulses would actually increase bandwidth due to sharp edges. Sinusoidal pulses minimize bandwidth.
知识点
PSK31, Sinusoidal pulses, Bandwidth minimization, Narrow-band digital
Verified Content
Question from official FCC Extra Class question pool. Explanation reviewed by licensed amateur radio operators.