By Bob Griffin (KC2JJM)
SETI — the Search for Extraterrestrial Intelligence.
Every ham’s logbook tells the same story in expanding circles. Across town on 2 meters. Across the country on 20. Across an ocean on a gray-line opening. Moonbounce, if you’re stubborn enough. Each ring is the same discipline — weak signals, patience, knowing your noise floor — applied to a longer path.
This is a story about chasing the outermost ring.
SIXTY-FIVE YEARS OF A DEAD BAND
First, the puzzle that drives the whole field. The Fermi paradox, in one line: a galaxy of hundreds of billions of stars, most of them billions of years older than the Sun, should be full of civilizations — so where is everybody? Enrico Fermi asked it over lunch in 1950, and it has not been answered since.
Since 1960, SETI has worked one way: point a big dish at a star and scan for a carrier near 1420 MHz, the hydrogen line — the natural calling frequency any radio-literate civilization could find. Project Ozma did it with one channel. SETI@home did it with millions of our PCs (I had that screensaver running in the shack for years; many of you did too). Breakthrough Listen does it today with billions of channels. Sixty-five years of better receivers have returned exactly one thing: silence. No confirmed carrier, ever.
Every ham knows what a dead band usually means. A band that sounds empty on a carrier scan can be carrying dozens of QSOs at 20 dB below the noise — you hear nothing because you’re listening for the wrong mode, not because nobody’s on the air. FT8 taught a whole generation of operators that lesson.
So here’s the question my project asks: what if the silence is a design feature? In the paper, we develop a new testable hypothesis, called Behavioral SETI, to explain the apparent radio silence.
THINKING LIKE THE SYSTEM DESIGNER
Suppose an advanced civilization wanted to reach emerging societies across the galaxy, over spans of millions of years. Design that system the way an engineer would and three decisions fall out. Build no transmitter — stars already radiate more power than any machine ever could; the cheap way to signal is to modulate sources already on the air. Write in ratios — a sender who shares no units with you can only use dimensionless relationships among measurements; the message isn’t on any one channel, it’s in how observables move together. Spend nothing on receivers who can’t act — gate the message behind a proof of capability.
If that’s the design, nobody hears it with a carrier scan. You find it by looking for behavior in sources that already exist — which means searching astrophysics archives, not the airwaves.
THE CRYPTOLOGICAL GATE
The strangest rule is the third one, and it deserves its own explanation. The framework predicts the message arrives locked: a short pointer tells you where to look, but the payload behind it is protected by what a cryptographer calls proof of work — a puzzle that is cheap to set, expensive to solve, and trivial to verify once solved. Why would anyone bother, across interstellar distances? Three reasons an engineer would insist on it.
First, the gate is a license exam that grades itself. A sender cannot proctor anything from thirty light-years away. Solving the puzzle certifies the receiver’s capability with no effort from the sender: if you opened it, you had the computers; if you had the computers, you have the industry and the science to act on what’s inside. Nobody unqualified can even read the question.
Second, it sets the timing automatically. Our own computing grew eight-billion-fold in one working lifetime — Cray-1 to Frontier, 1976 to 2022. A gate pitched at industrial-scale computing opens within a generation of a civilization first noticing it. The lock is a fuse, timed by the receiver’s own growth — no schedule, no appointments, nothing that can go stale over a million years.
Third, the unlock is authentication. When the receiver transmits the solved key back, that transmission proves the work was actually done — no spoofing, no accidental triggers, no energy wasted answering noise. In ham terms: the gate is the ultimate CTCSS. Except this tone can’t be looked up in a manual. It can only be earned.
WEAK-SIGNAL DISCIPLINE, APPLIED TO ARCHIVES
So that’s what I did: 49 searches across public archives — GOES X-ray satellites, neutron monitors, pulsar timing arrays, Voyager’s magnetometers, solar neutrino detectors. And here’s the part I’d defend at any club meeting: the methods are ham methods. Long integration to pull signals out of noise. Measuring the noise floor before claiming anything sits above it. And never trusting the rig without a test signal — every detection limit is verified by injecting synthetic signals and confirming the pipeline recovers them. The whole campaign’s positive control was recovering the Sun’s known five-minute oscillations from satellite data — the WWV of the project. If your system can’t hear the known signal, your silence means nothing.
The score: 45 nulls with measured limits, and no contact. In this business a calibrated null is the product.
THE EMAIL TO JAPAN
My favorite result wasn’t in any dataset. One channel needed solar-neutrino data from Super-Kamiokande, the great detector in a mine in Japan. The public link had been dead for years. So I wrote to the collaboration — callsign in the signature, one ham asking about data. The spokesperson answered the next day, pointed me to a public 22-year dataset better than the one I’d asked about, and committed to fixing the dead link. We ran the search within 48 hours. Null, with limits — and the first time anyone had asked that dataset an aperiodic question. QSL received, you might say.
HOW FAR DO OUR SIGNALS GET?
A 2025 SETI Institute study ran the honest numbers on Earth’s own detectability, and hams will appreciate the EIRP ladder: Arecibo’s planetary radar, at 20 terawatts EIRP, would stand out at 12,000 light-years. The Deep Space Network: 65. The combined mobile-phone leakage of the entire planet: 4. The loudest thing humanity ever put on the air was pinging asteroids. Everything we broadcast to each other barely leaves the neighborhood — one more reason silence proves so little.
And one thought I can’t shake, as an AM DX’er myself: the earliest thing any radio civilization transmits is its lowest bands. A designed listening post watching for emerging civilizations wouldn’t need to decode a 1930s 500 kW AM flamethrower like WLW — just detect the carrier, coherently integrated, far below any demodulator’s threshold. Carrier detection at absurd SNR is a very ham idea. The paper takes it seriously.
GOING DEEPER
The write-up, a six-minute animated version, and the full paper with every method and limit are here:
https://dxtra.com/static/galactic-dx/summary.html?src=hamdaily
Source: KC2JJM
Amateur Radio Daily