宇宙微波背景辐射
An indoor antenna may include an amplifier circuit, whereby powered reception of the signal can help with capturing as much of an FM, UHF/VHF signal, for amplifying a radio or television signal. Its draw backs are that any noise is usually amplified as well, and a common result from this is amplification of ghost images (for analog signals), and any other perturberances that may be existing locally or even extra terrestrially like the Cosmic microwave background radiation for devices that work in that frequency range.