What does shortwave radio signal 4 mean?

Shortwave radio signal 4 usually refers to frequency band 4 in international radio broadcasts, also called the 16MHz band. This frequency band is a relatively high-frequency shortwave frequency band with relatively stable propagation effect and is suitable for some long-distance communications, such as ship and aircraft communications.

In addition to communications, shortwave radio signals 4 are also used in some astronomical research. Because signals in this frequency band can penetrate the Earth's atmosphere, it plays an important role in the study of charged particles such as solar wind. At the same time, scientists also use shortwave radio signals 4 to observe the ancient universe and explore the evolution history of the universe.

In some emergency situations, shortwave radio signals 4 can also be used to send emergency rescue signals. Many countries have established corresponding emergency rescue frequencies to rescue people in unexpected situations. The signals in these frequency bands have strong penetrating power and can be received by rescue teams in distant places. At the same time, this emergency rescue signal can also prevent other ships and aircraft from approaching the accident scene to ensure the rescue effect.