What should you check before transmitting on an EF Johnson radio?

The correct choice emphasizes the importance of conducting a thorough check of various essential settings before transmitting on an EF Johnson radio. By confirming the channel, transmission power (TX PWR), scan settings (ensuring that the scan is off), and the squelch (identified as "Sel SQ"), you ensure that the radio operates correctly and efficiently in the intended communication environment.

Each of these settings plays a critical role in effective radio communication. The channel selection ensures that you are on the correct frequency for communication. Adjusting the TX PWR is vital for optimizing the signal strength based on distance or environmental factors. Turning off the scan feature is crucial when you want to maintain a constant connection on a fixed channel, rather than have the radio continually searching for signals on other channels. Lastly, setting the squelch properly helps eliminate background noise, allowing for clearer communication.

In comparison to the other options, focusing solely on channel settings, microphone placement, or battery charge would not adequately prepare you for effective transmission, leaving out critical components that impact the quality and reliability of the communication process.