Also known as: low-noise amplifier, LNA

A low-noise amplifier (LNA) boosts a weak antenna signal early in the receive chain, adding as little noise as possible.¹ Because later stages add their own noise, amplifying first preserves SNR.

A low-noise amplifier boosts the faint antenna signal early, setting the receiver's sensitivity.

How it works

An LNA’s noise figure largely determines how weak a signal the whole receiver can detect — its sensitivity. It is best mounted at the antenna, often powered through the coax by a bias tee.

Relevance to SDR

An antenna-mounted LNA can meaningfully improve reception of weak signals, especially with lossy cable runs — but watch for overload from strong nearby transmitters.

Sources

1. Low-noise amplifier — Wikipedia, on LNAs, noise figure, and their role in setting receiver sensitivity. ↩

See also

• Noise floor
• Signal-to-noise ratio (SNR)
• Superheterodyne receiver
• Bias tee
• Antenna

Learn it step by step

• How an SDR receiver works