Question
Which of the following is the best instrument to use for checking the keying waveform of a CW transmitter?
Answer Options
- A) An oscilloscope
- B) A field strength meter
- C) A sidetone monitor
- D) A wavemeter
Correct Answer: A
Explanation
The keying waveform of a Continuous Wave (CW) transmitter must be properly shaped to prevent the generation of ‘key clicks,’ which are spurious sidebands caused by instantaneously turning the RF on and off. Checking this waveform requires analyzing the shape of the signal’s envelope in the time domain.
The oscilloscope is the best instrument for this task. By sampling the transmitter’s RF output and displaying the envelope (voltage vs. time) when the operator keys down, the oscilloscope allows the operator to visually inspect the signal’s rise and fall times to ensure they are smooth and not too fast, which would cause the unwanted clicks.
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