*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 check the keying waveform of a CW (Continuous Wave) transmitter, you need to visualize the waveform to ensure it is clean and free of distortion. Here's why an oscilloscope is the best tool for this task:

1. **Correct Answer: An oscilloscope**
   - An oscilloscope allows you to visually inspect the waveform of the transmitted signal. You can see the rise and fall times, the shape of the waveform, and any distortions or irregularities. This is crucial for ensuring that the CW signal is being transmitted cleanly and efficiently.

2. **Why the other choices are incorrect:**
   - **A field strength meter**: This instrument measures the strength of the transmitted signal but does not provide any information about the waveform shape. It cannot show you the keying characteristics.
   - **A sidetone monitor**: This device allows you to hear the transmitted signal, typically used for monitoring your own CW transmissions audibly. It does not provide a visual representation of the waveform.
   - **A wavemeter**: This is used to measure the frequency of a signal, not the waveform shape. It is not suitable for checking the keying waveform.

3. **Useful Information:**
   - When using an oscilloscope, you can check for keying waveform issues such as "key clicks," which are unwanted sidebands caused by rapid changes in the waveform. A clean CW waveform should have smooth transitions without excessive overshoot or ringing.

In summary, an oscilloscope is the best instrument for checking the keying waveform of a CW transmitter because it provides a visual representation of the signal, allowing for detailed analysis of its shape and quality.