Ham Amateur Radio Technician Practice Exam

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

1. An audio spectrum analyzer

2. An oscilloscope

3. A digital multimeter

4. A frequency counter

The correct answer is: An oscilloscope

An oscilloscope is the best instrument to use for checking the keying waveform of a continuous wave (CW) transmitter because it provides a visual representation of the voltage signal over time. This allows you to observe the characteristics of the keying waveform, such as its amplitude, frequency, and the shape of the waveform itself. By examining these aspects, you can determine whether the CW signal is being transmitted correctly, including the rise and fall times of the keys, the presence of any distortion, and whether the signal's timing is accurate. Furthermore, an oscilloscope can display modulated waveforms in real time, enabling you to see how the signal behaves minute-to-minute or even second-to-second. This level of detail is crucial in ensuring the quality of the transmission and making necessary adjustments to maintain a clean and legitimate signal in CW operation. In contrast, other instruments mentioned, such as an audio spectrum analyzer, while useful for analyzing audio frequencies, do not specifically measure keying waveforms effectively. A digital multimeter primarily measures voltage, current, and resistance but lacks the capability to visualize waveforms or analyze the timing characteristics accurately. A frequency counter simply measures the frequency of a signal and does not provide information about the shape or timing of the waveform.