Can I buy an amplifier by itself? Or do I have to buy a complete kit?

The FCC requires that all amplifiers must be sold as part of a kit and cannot be sold individually.

The FCC passed regulations on cell phone signal boosters that went into effect in 2014 mandating that all signal booster amplifiers must be sold as part of an entire kit, including antennas and cables, and can not be sold individually. Since then, all signal booster amplifiers have been required to be sold as a complete kit, even for situations where just an amplifier needs to be replaced in an existing system.