What signal source is connected to the vertical input of an oscilloscope when checking the RF envelope pattern of a transmitted signal?
The correct answer is D: The attenuated RF output of the transmitter. The signal source connected to the vertical input of an oscilloscope when checking the RF envelope pattern of a transmitted signal is the attenuated RF output of the transmitter. You need to attenuate the RF output to a safe level for the oscilloscope. For amateur radio operators, this is how you monitor transmitted signals. Understanding this helps when checking transmitter output.
Exam Tip
Check RF envelope = attenuated RF output of transmitter. Think 'R'F 'E'nvelope = 'R'F 'E'xit (output) attenuated. Connect attenuated RF output of transmitter to oscilloscope vertical input. Not local oscillator, external oscillator, or mixer - just attenuated RF output.
Memory Aid
"Check RF envelope = attenuated RF output of transmitter. Think 'R'F 'E'nvelope = 'R'F 'E'xit attenuated. Connect attenuated RF output to oscilloscope vertical input. Must attenuate RF to safe level for oscilloscope."
Real-World Application
You want to check the RF envelope pattern of your transmitter. You connect the attenuated RF output (using a proper RF attenuator) to the oscilloscope's vertical input. The oscilloscope displays the RF envelope, showing you modulation characteristics. The RF must be attenuated to a safe level for the oscilloscope.
Key Concepts
Why Other Options Are Wrong
Option A: Incorrect. Local oscillator output isn't the RF envelope - that's an internal signal, not the transmitted signal. You need the actual RF output.
Option B: Incorrect. External RF oscillator isn't needed - you want to check your transmitter's output, not an external signal. External oscillator doesn't show your transmitter's envelope.
Option C: Incorrect. Balanced mixer output isn't the RF envelope - that's an internal signal before final amplification. You need the final RF output.
题目解析
The correct answer is D: The attenuated RF output of the transmitter. The signal source connected to the vertical input of an oscilloscope when checking the RF envelope pattern of a transmitted signal is the attenuated RF output of the transmitter. You need to attenuate the RF output to a safe level for the oscilloscope. For amateur radio operators, this is how you monitor transmitted signals. Understanding this helps when checking transmitter output.
考试技巧
Check RF envelope = attenuated RF output of transmitter. Think 'R'F 'E'nvelope = 'R'F 'E'xit (output) attenuated. Connect attenuated RF output of transmitter to oscilloscope vertical input. Not local oscillator, external oscillator, or mixer - just attenuated RF output.
记忆口诀
Check RF envelope = attenuated RF output of transmitter. Think 'R'F 'E'nvelope = 'R'F 'E'xit attenuated. Connect attenuated RF output to oscilloscope vertical input. Must attenuate RF to safe level for oscilloscope.
实际应用示例
You want to check the RF envelope pattern of your transmitter. You connect the attenuated RF output (using a proper RF attenuator) to the oscilloscope's vertical input. The oscilloscope displays the RF envelope, showing you modulation characteristics. The RF must be attenuated to a safe level for the oscilloscope.
错误选项分析
Option A: Incorrect. Local oscillator output isn't the RF envelope - that's an internal signal, not the transmitted signal. You need the actual RF output. Option B: Incorrect. External RF oscillator isn't needed - you want to check your transmitter's output, not an external signal. External oscillator doesn't show your transmitter's envelope. Option C: Incorrect. Balanced mixer output isn't the RF envelope - that's an internal signal before final amplification. You need the final RF output.
知识点
Oscilloscope, RF envelope pattern, Attenuated RF output, Transmitter monitoring
Verified Content
Question from official FCC General Class question pool. Explanation reviewed by licensed amateur radio operators.