Before testing a RADAR transmitter, it would be a good idea to:

Testing a RADAR transmitter involves generating high-power microwave signals that can pose safety risks, particularly in environments where explosives or flammable materials are present. Ensuring that there are no explosives or flammable cargo being loaded is crucial to prevent potential accidents or fires during the test. The high-energy output of the RADAR system could ignite flammable materials or trigger an explosive device if these safety precautions are not adhered to.

While ensuring the safety of personnel on deck and notifying relevant authorities are also important considerations, they do not directly address the specific risks associated with testing a RADAR transmitter in an area where hazardous materials are present. Thus, confirming that the testing area is free of such dangerous materials is the most critical step for both safety and compliance with safety protocols.