Final answer:
In emergencies at sea, one issues a MAYDAY on Channel 16 while the distance radio messages can travel is influenced by antenna height and radio power. Mobile phones must be turned off in certain environments to prevent interference with critical communication systems or medical equipment.
Step-by-step explanation:
When facing a life-threatening emergency at sea, it is critical to ensure everyone's safety by having them put on Personal Flotation Devices (PFDs) and by issuing a MAYDAY call on Channel 16. The effectiveness of sending and receiving distances for these messages largely depends on the height of the antenna and the power of the radio used. Typically, the radio should be set to use one-watt power to avoid interference, but in emergency situations or if the signal is too weak, higher power settings may be used to ensure the message is received clearly.
The relevance of mobile phones being switched off on airplanes or in hospitals is due to the potential interference their signals, which often operate around 1.9 GHz, can cause to important communications systems or medical equipment that may operate on similar frequencies. Moreover, this example illustrates the broader concept of how various devices utilize radio frequencies and the importance of managing those frequencies to avoid cross-interference.
Understanding the basics of radio communication, including channels, signal strength, and interference, is essential for the maintenance of safety in various environments such as sea navigation, aviation, and medical settings.