Unusual Signals
The short wave bands are also used by unlicensed individuals who may want mostly short-range "party line" like communications. Two examples are the use of HF for communication between fishing boats in many areas of the world, and the unlicensed use of the 11-meter band, which is effectively permitted in some areas of the world. Unlicensed operators, called "pirates", can cause signal interference to licensed stations. Many third-world countries have shops selling HF transmitter radios to any customer without regard to license or operator knowledge. As of 2012, there were virtually no national or international efforts to control such pirate operations.
The short wave bands are also used for various experiments, some continuing for years. In 2011, signals traceable to China regularly sent powerful HF transmissions scanning wide ranges of HF frequencies, perhaps to determine the maximum usable frequency (MUF) or other variables.
Read more about this topic: Shortwave Radio
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