The International telecommunications Union, ITU frequency bands define a set of portions of the radio frequency spectrum: VLF, LF, HF, VHF, UHF, EHF, etc .
Frequency spectrum
eCFR :: 47 CFR Part 2 -- Frequency Allocations and Radio Treaty Matters; General Rules and Regulations
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Frequency Nomenclature (.PDF Download)
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ITu Communication band designation chart showing the Terahertz
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