LNA vs LNB

They sound similar, but they serve different purposes in the signal chain:

What it is: An electronic amplifier that boosts very weak signals while adding as little noise as possible.
Where it’s used: Placed as close to the antenna feed as possible (for radio astronomy, satellite comms, RF front-ends).
Function:
- Amplifies the weak RF signal from the antenna.
- Designed to have a very low noise figure (so it doesn’t swamp the signal with amplifier noise).
- Keeps the system noise temperature low.
Output: Still at the original RF frequency.

What it is: A device that combines an LNA with a frequency downconverter.
Where it’s used: Common in satellite TV dishes and radio astronomy front ends at microwave frequencies.
Function:
- First, the LNA inside the LNB amplifies the weak microwave signal.
- Then, a local oscillator (LO) and mixer shift (downconvert) the frequency from a high microwave band (e.g. 10–12 GHz for Ku-band TV, or 1.42 GHz in hydrogen-line astronomy if custom-made) down to a lower intermediate frequency (IF).
- The IF is easier to transport over coax and to process with standard receivers or SDRs.
Output: A lower-frequency version of the signal, already amplified.

✅ In short:

An LNA just amplifies at the original RF frequency.
An LNB is an LNA plus a frequency downconverter, producing a lower IF output suitable for long coax runs and consumer-grade receivers.