There’s a sense of urgency in the air at a Virginia nuclear power plant. Everything within at least a five-mile radius is at immediate risk due to a critical meltdown. One of the emergency responders opens the envelope she’s holding, scans its contents, and announces the bad news: “We just lost 911 and the cell towers are overloaded.”

There are some groans, but the team of amateur radio operators knew this was a possibility, and they’re prepared. They have their radios at the ready to coordinate evacuations, making sure that no shelters are overwhelmed and that evacuees arrive at the right locations. Two detach themselves from the rest and make their way over to the lead coordinator. They’re acting as the points of contact for all emergency services, which means they’re responsible for relaying information about everything from fires to urgent medical care to illegal activities.

It’s no small task, especially when there’s a nuclear meltdown in the background, but this isn’t the first time these radio operators have tackled a problem of this scale: Similar disasters happen every two years, after all. This time, it’s an earthquake that caused a cooling tower to fail. Sometimes it’s a terrorist attack, or perhaps a hurricane. Fortunately, none of these are real disasters: They’re Simulated Emergency Tests (SET), mock disasters that radio-operator groups use to show the typical emergency players—police, the Red Cross, FEMA—that when the worst happens, these hobbyists can be an essential part of the response.

The moniker “ham” as a nickname for amateur radio operators was initially an insult: Professional broadcasters referred to these amaterus as “” as ham-handed. But the newly dubbed hams didn’t let that stop them. Amateur radio operating took off at the beginning of the 20th century; by 1910, there were thousands of amateur radio operators, and things were getting noisy. Shoddy workmanship on homemade radios caused disruptive signals across all the bands of radio waves: The signal scattered like drops of paint, splattering onto other nearby bands and disrupting their communications.

The volume of chatter and the potential for disruptions to communications led to the Radio Act of 1912, which required amateur radio operators to be licensed and restricted them to use only a single short wavelength. Around 88 percent of hams quit the hobby, thinking this band too weak and too short to allow them any real fun.

The ones that stuck with it, though, were a dedicated lot. In 1914, Hiram Percy Maxim figured out that you could successfully transmit radio messages across long distances if you had other ham radio operators along the way to leapfrog the signal. He created the American Radio Relay League (ARRL) to organize hams across the nation.

Today the United States is home to more than 700,000 licensed amateur radio operators (including every member of my immediate family—I’m the only one without a ham-radio license, having failed the lowest-level technician test).

Around 40,000 of them are part of the Amateur Radio Emergency Service (or ARES, pronounced like the god of war), a subset of the ARRL. There are branches all over the country, and ARES members are the hams that show up at the simulated disasters, ready to relay information wherever it needs to go. They helped out during disasters like Hurricanes Katrina and Sandy and the 9/11 terror attacks—they were the ones getting messages out even after the cellphone towers went down, overloaded by the family members of World Trade Center employees trying to reach their loved ones.

“Our primary mission is to work with local operations to assist with communications when normal means fail to function,” says Michael Corey, the national coordinator for ARES. They do this on three main levels: the local level, which would cover disasters like a nuclear meltdown; state level, which would cover more widespread menaces like hurricanes; and the national level, which might involve a mass evacuation in the event of a devastating hurricane or the loss of national communications services due to space weather events.

If you live in a hurricane-vulnerable region like the mid-Atlantic or the Gulf coast, you’ve likely benefited from ARES’s presence. “Hurricanes tend to take out large chunks of infrastructure for short periods of time,” explains Corey. “There’s about a 72-hour window when normal infrastructure is not operating at its optimum level. In a hurricane, the hams will come in and basically set up those temporary networks until other backup systems can be brought online.”

The advantages of ham radios in a disaster situation are twofold: They’re free from large infrastructure, and they’re incredibly flexible bits of technology. “An emergency operation system might need a big generator to keep things going, but we can get by with batteries or solar power,” Corey explains. If a natural or man-made disaster takes out power, Internet, or phone lines,  “We can do global communications with nothing between the two systems but ether.”

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Eugene Spafford, a computer-science professor at Purdue University  and a member of the Naval Academy’s Cybersecurity Advisory Board, has been thinking about all the ways computers work (and fail) since 1979. “So many [technologies] are interconnected in ways we don’t see,” he says, “that a longer shutdown lasting weeks or months would be catastrophic.”

A key example: global positioning systems, better known as GPS. If you were to lose your ability to use GPS to find directions, it’d be an inconvenience. But if emergency services—ambulance drivers, firefighters, and police— were to lose their navigational ability, it could be deadly.

GPS also plays a key role in time synchronization. Power plants, for example, use GPS to ensure that their generators are emitting electrical currents in sync. Mistimed generators can lead to burnt-out unusable equipment, power failures and fires.

But the satellite system that controls such essential functions isn’t foolproof.  “A solar flare, certain kinds of attacks that can be committed from the ground, or a hostile nation using anti-satellite weapons could take out our satellite system,” Spafford says. “And because those require a space launch of custom built satellites, we couldn’t just turn those on a day later.” In this hypothetical disaster scenario, that translates to a sustained time without cellphones or GPS-coordinating emergency services, and even the possibility of rolling blackouts.

Radios, though, would continue functioning. “We more or less know how to do the same thing[s these technologies do] without technology, but we’ve forgotten how to do it,” says Spafford. “It’s called deskilling.”

In the digital age, “we’ve run into a lot of deskilling,” he says. “Many people used to be able to remember phone numbers or have phone books, for example—now we look it up online. If that went away, what would we use?”

There are measures in place to make sure we don’t need to find out: There are usually a few spare satellites in orbit,  our electric grid is cleverly designed in disconnected pieces. In the case of a cyberattack, it’s unlikely that all of a region (or even most of it) would go dark, as the power systems would be able to disconnect from each other and still generate power.

But a more resilient infrastructure, Spafford explains, would be one with low-tech backups in place, too. Power failures are devastating because the general public doesn’t know how to live without power. “If we had a power failure that shut off all the gas pumps for a month, the Amish would probably survive just fine,” Spafford points out. “It isn’t a matter of training them for that eventuality, it’s that’s the way they live.”

Clearly, he isn’t advocating that everyone start building sturdy furniture in Pennsylvania. But what he’s describing, a trained segment of the population that can keep going when infrastructure fails, sounds a whole lot like ARES.

Ham-radio operators, at least the ones who volunteer for ARES, are in some ways an antidote to Spafford’s deskilled millions. The best ones are also using their radios all the time, that if disaster strikes they’ll be ready to spring into action.

“What makes us useful is the things we do when nothing is happening, when no big events are going on, and then using the skills we learn through regular practice to assist during a crisis to add capability and capacity,” Corey explains.

The ARES member Reid Barden, 20, is one such ham who makes it a point to stay sharp. Barden is the president of the Virginia branch of the Amateur Radio Communication Association (ARCA) and the founder of Virginia Commonwealth University’s Amateur Radio Club. Several weekends each year, he volunteers at events like Special Olympics, MS Society bike events, and marathons—events that rely on teams of hams to communicate when an athlete goes missing or a runner needs medical attention.

Volunteering is in many ways at the heart of ham radio. There’s no commercial aspect to the hobby—hams aren’t paid for their work. There’s a reason thousands of hams across the nation spend their time helping out at bike events or to do disaster drills: They need to make themselves present to demonstrate just how essential their skills really are. The average person doesn’t like dwelling on the worst-case scenario. But when and if one happens, the most dedicated hams will be ready, radios in hand, to turn a quirky hobby into a network of lifesavers.