CERN Amateur Radio Club – CARC

Shortwave utilities monitoring

Beyond the Broadcast: Exploring Shortwave Utility Signals, Number Stations, and Ham Radio

There’s a whole world hiding between the crackles and tones of shortwave radio—and if you’re only tuning in for international broadcasters or ham QSOs, you’re missing out on some of the most fascinating parts of the spectrum. Welcome to the world of shortwave utility monitoring, where you’ll find aviation weather, military signals, coast guard bulletins, and yes—even mysterious number stations whispering coded messages into the static.

If you’re a ham radio operator or an SWL (shortwave listener), utility DXing is like treasure hunting in the ionosphere. With the right setup—often as simple as a portable receiver and a long wire—you can eavesdrop on the beating heart of global infrastructure and espionage from your own backyard.

What Are Shortwave Utility Signals?

Utility signals are non-broadcast, non-amateur communications on the HF (3–30 MHz) bands. That means:

  • Aviation: HF ATC (Air Traffic Control) for oceanic flights (like New York Radio on 10051 kHz)
  • Marine: NAVTEX and weather broadcasts, distress communications, ship-to-shore traffic
  • Military & Diplomatic: Encrypted digital modes, schedules, and mysterious unannounced chatter
  • Telemetry & Beacons: From time stations like WWV to propagation beacons and telemetry bursts
  • Number Stations: Those odd, monotone voices repeating coded messages at scheduled times… still active and still unexplained.

Getting Started with SWL and Utility Monitoring

The great part about shortwave utility monitoring is how approachable it is. You don’t need an expensive setup to start exploring.

Starter gear might include:

  • A portable shortwave radio with SSB support like the Tecsun PL-660, Sangean ATS-909X, or XHDATA D-808
  • A simple long wire or dipole antenna—even clipped to your curtain rod
  • Optionally, an RTL-SDR dongle or SDRplay receiver for digital decoding and waterfall displays
  • Decoding software such as Fldigi, MultiPSK, DSCDecoder, or SigIDWiki for identifying digital modes

And of course, a logbook—because once you start logging stations like “Shanwick Oceanic HF Control” or “Mysterious Digital Burst on 9150 kHz,” it becomes addictive.

Ham Radio Meets SWL: The Overlap

If you’re a licensed ham, you’re already familiar with the rhythm of HF. Utility listening brings a different flavor—it’s mostly one-way, passive, and strange. But it’s also an excellent way to sharpen your:

  • Band awareness: Knowing propagation windows and gray-line effects
  • Mode decoding skills: Many digital utility transmissions use modes like PSK, FSK, RTTY, STANAG, and even OLIVIA or MFSK
  • Antenna performance: Because some of these signals are faint and far, perfect for tuning and testing

Many hams blend SWL and transmitting hobbies. On a quiet band, it’s fun to shift gears from FT8 to monitoring a Russian weather fax or a UN diplomatic relay in SITOR-B.

And Then There Were Numbers…

No utility DX post is complete without a nod to number stations—those eerie transmissions of computer-generated voices, bursts of tones, and coded sequences. Once thought relics of the Cold War, many are still active, possibly maintained by intelligence agencies for one-way messaging to field agents.

Some of the more famous ones include:

  • The Buzzer (UVB-76): A buzzing sound interspersed with coded voice messages (4625 kHz)
  • Lincolnshire Poacher: A now-defunct but legendary British station with a cheery interval tune and eerie numbers
  • E10 “Mossad” stations: Often heard in AM or USB, broadcasting from the Middle East and Eastern Europe

You can find live logs and schedules on:

Why It’s Worth Your Time

Shortwave utility monitoring connects you to the hidden infrastructure of the world. You’re not just a passive listener—you’re decoding fragments of real-time global communication. And unlike much of modern life, it’s all off the grid and fully under your control.

It’s the side of radio where weather meets war, where shipping reports brush up against spy messages, and where you, the operator, become the link in the listening chain.

So whether you’re a ham with a Yaesu base station, an SDR tinkerer with a Raspberry Pi, or a night owl with a $50 shortwave radio and a wire on the porch—there’s a whole spectrum out there whispering utility signals into the night. Go chase them.

Recommended Links for the Curious: