*Question G4B03:
Which of the following is the best instrument to use for checking the keying waveform of a CW transmitter?*  

*Correct Answer is  A: An oscilloscope*  

### AI Response: (may contain errors)  

To determine the best instrument for checking the keying waveform of a CW transmitter, let's analyze the options:

### Correct Answer: A: An oscilloscope

- **Why it's correct**: 
  - An oscilloscope is designed to visualize electrical waveforms. It allows you to see the shape of the keying waveform, which is crucial for ensuring that the transmitter is keying properly. You can observe the rise and fall times, the duration of the keying, and any distortion in the waveform, which are all important for effective CW operation.

### Why the other choices are incorrect:

- **B: A field strength meter**:
  - A field strength meter measures the strength of the radio signal in the field, not the waveform of the keying signal. It cannot provide information about the shape or timing of the keying waveform.

- **C: A sidetone monitor**:
  - A sidetone monitor allows the operator to hear the transmitted CW signal as a tone, but it does not provide a visual representation of the keying waveform. It is useful for monitoring the audio output but not for analyzing the waveform itself.

- **D: A wavemeter**:
  - A wavemeter is used to measure the frequency of a signal, not the waveform. While it can help ensure that the transmitter is operating on the correct frequency, it does not provide information about the keying characteristics.

### Summary:
- The oscilloscope is the best choice for analyzing the keying waveform of a CW transmitter because it provides a visual representation of the waveform, allowing for detailed analysis of its characteristics. The other instruments serve different purposes and do not provide the necessary information about the keying waveform.