Preamplifiers or preamps are low noise amplifiers that mount to (or close to) an indoor or outdoor antenna to improve weak signals. Booster amps are high gain amp's used for overcoming long cable runs. Distribution amp's are low to moderate gain amp's used for multiple connections (TV's).
Preamps are low noise amplifiers, amplifies signal but not noise. Indoor antenna preamps are a single unit mounted to the antenna. Outdoor preamps are 2 piece units, an amplifier mounted close to the antenna, and a power unit inside the home that supplies power to the amplifier through the coax cable. The closer the amplifier unit is to the antenna, the greater the signal improvement. Signal improvement is the preamp gain minus the Noise Figure minus cable loss (between the antenna and amp unit). The lower the preamp noise figure (NF) and the shorter the cable, the better. Signal improvement can be 15 to 20 dB or more. Some outside antenna's have a built-in preamp to maximize performance.
The power unit uses standard house current (110 Vac), some can also get power from a USB connection. The power unit supplies direct current (DC) power to the amplifier through the coax cable center conductor. There can only be cable between the preamp and the power unit, no splitters/combiners or impedance matchers. Coax ground blocks (for lightning and static protection) and cable connectors can be used if they pass DC power (most do).
Preamps come with either a fixed gain or an adjustable gain, most cover the VHF and UHF bands, some are indoor only, some can be mounted outside. Some preamps have an FM Trap to filter out the commercial FM radio band which is between RF channels 6 and 7. The filter may be needed if an FM signal is strong enough to overpower the preamp reducing it's performance. Some FM traps reduce RF channel 6 reception. Some preamps also filter out the 4G and 5G mobile communication bands.
BOOSTER & DISTRIBUTION AMPLIFIERS
Booster amps are high gain amplifiers (20 dB or more) used to overcome long cable runs. Distribution amps are moderate gain amplifiers (3 to 8 dB) with multiple outputs used for cable systems with multiple outlets. Some amplifiers are fixed gain, some are adjustable. The amplifiers use standard house current (110 Vac).
A signal that is too strong can overwhelm (saturate) a TV receiver, causing signal distortion (cannot decode signal). An attenuator can reduce the signal to an acceptable level. Some attenuators have a fixed reduction, some are adjustable.
Over-the-Air Digital TV (OTA DTv)