Which of the following is NOT a default issue when using a radio?

Device weight is not a default issue when using a radio because it is more about the physical characteristics of the device rather than its operational functionality. Radios are designed with a specific weight profile that often varies by model and purpose, but this does not directly affect the communication capability or reliability as the other factors do.

In contrast, frequencies and range, signal clarity, and battery life are fundamental aspects that can significantly impact radio operations. Frequencies and range refer to the specific channels that can be used and how far the radio can effectively communicate. Signal clarity relates to the quality and intelligibility of the transmitted signals, while battery life ensures that the radio can operate efficiently for the desired duration of use. Therefore, while weight can be a consideration for comfort and portability, it does not intrinsically influence the radio's performance in communication scenarios.