each frequency range has a band designator and each range of frequencies behaves differently and performs different functions. The frequency spectrum is shared by civil, government, and military users of all nations according to international telecommunications Union (ITU) radio regulations. for communications purposes, the usable frequency spectrum now extends from about 3Hz to about 300GHz. There are also some experiments at about 100THz where research on laser communications is taking place but we won't discuss this now. This range from 3Hz to 300GHz has been split into regions. The good thing is that once this range has been split it remained that way and became standard. And it is up to you want to accept this standard or not. Frequency band standard is described in international telecommunications Union radio regulations. And it looks as follows.