Interesting piece by ChatGPT about sensitive receivers

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Here's a breakdown by category so you can see what really pushes the limits of sensitivity:

🔭 Ultimate sensitivity (radio astronomy)

World's most sensitive "receivers" overall are the radio telescope front-ends used in arrays like:

ALMA (Atacama Large Millimeter/submillimeter Array) — noise figures down to <5 K system noise temperature at 100 GHz!

SKA (Square Kilometre Array) — designed to have a system equivalent flux density (SEFD) of just a few Jy (10⁻²⁶ W/m²/Hz), effectively the quietest radio receivers ever made.

Cryogenically cooled LNAs (liquid helium or nitrogen cooled) inside these receivers can reach noise figures <0.05 dB (yes, that's not a typo).

These are used for detecting signals weaker than 10⁻²⁴ W — literally from galaxies billions of light-years away.

📡 Laboratory / experimental communications

In communications and weak-signal work, some of the most sensitive setups are:

Deep Space Network (DSN) receivers — used by NASA to pick up Voyager 1/2 signals ~22 billion km away.

Effective noise temperature ~15 K

Receiver sensitivity around –260 dBm in Hz bandwidth, or about –160 dBm in 1 Hz SNR=1.

SETI receivers (like at Green Bank) — similar cryogenic front-ends with software-defined back-ends capable of detecting femtowatt-level carriers.

🛰� Amateur / practical extreme

For something you could build or use:

State-of-the-art microwave LNA chains (with pHEMT or InP transistors) can reach 0.2 dB NF at 1–3 GHz, giving a minimum detectable signal around –165 dBm/Hz.

Modern SDRs like the Perseus, Airspy HF+ Discovery, or SDRplay RSPdx have noise floors in the –140 to –155 dBm range (in narrow bandwidths).

E-ME / moonbounce stations often run cryo LNAs to detect signals around –150 dBm after path loss of ~250 dB.

🧠 So, in short:
Application   Receiver Example   Sensitivity
Radio astronomy   ALMA, SKA   < –270 dBm (narrowband equivalent)
Space comms   NASA DSN   ~ –260 dBm
Amateur microwave   Cryo LNA + SDR   ~ –165 dBm
Consumer HF SDR   Airspy HF+   ~ –155 dBm