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What is Shortwave Radio?

Most Americans have only a vague understanding of shortwave radio. Some confuse SW radio with ham radio. Ham radio is a 2-way service (hams talking to other hams). ‌In contrast SW radio is a broadcast service. Shortwave stations transmit news, music and information to millions of people across the world. It is often called "International Shortwave" because unlike local AM and FM radio, shortwave uses an upper layer of the atmosphere (ionosphere) to bend signals to far flung areas of the globe.
Many folk wonder why it's called "shortwave" radio. The radio spectrum has been arbitrarily divided up into segments based upon frequency - LF, MF, HF, VHF, UHF, etc. The MF (medium frequency) range is from 300 kHz to 3000 kHz (3 MHz).  This section of the spectrum is probably the most familiar because the AM broadcast band (540 kHz to 1700 kHz) resides there. Electromagnetic (radio) waves in the AM band range in length from 556 meters at the lowest frequency (540 kHz) to 176 meters at the highest (1700 kHz). Notice that the radio wavelengths become shorter as the frequency increases.
As we go up in frequency in the spectrum the next segment is called "high frequency," abbreviated by the letters "HF." This segment covers from 3 MHz to 30 MHz. The HF range is where shortwave broadcasting takes place. And the wavelengths are indeed shorter than those used in the AM broadcast band. Shortwave broadcasters use numerous segments (bands) scattered throughout the HF range. All radio waves in the HF range are shorter than those used in the familiar AM broadcast band - thus the term "shortwave." How "short" are the wavelengths? Some popular shortwave bands are 49 meters, 31 meters, and 25 meters. As you can see shortwave radio uses wavelengths measured in tens of meters rather than hundreds of meters (like the AM broadcast band).

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