When a nuclear bomb goes off in a movie, audiences expect one of two things: a fiery explosion that wipes out a city, or total technological collapse across the country.
In Homestead, a nuclear bomb was detonated just off the coast of Los Angeles. Power went out. Some cell service failed or faltered, but the rest of the nation didn’t go dark... at least not initially.
That made some viewers cry foul. But the truth is, what we showed was realistic. Most people conflate a ground-level nuclear detonation with a High-Altitude Electromagnetic Pulse (HEMP) or EMP for short.
Here is the reality of the threat, debunking the biggest myths, and actionable steps to protect your gear.
The Science: Why Not All Nukes Are EMPs
EMP stands for Electromagnetic Pulse—a burst of energy that creates a voltage surge in electrical circuits. While all nuclear detonations create an EMP, the altitude matters enormously.
1. Ground-Level Detonation (The Standard Nuke)
If a bomb hits a city, the primary threats are blast, heat, and radiation. The EMP effect is intense but localized—typically limited to a 2–5 mile radius. If you are close enough for the EMP to fry your phone, you likely have much bigger problems to worry about (like the shockwave...and instant death).
2. High-Altitude EMP (HEMP)
This is the nightmare scenario. A weapon detonated 20–250 miles above the Earth interacts with the magnetic field to cover a massive area (potentially the entire continental U.S.).
A HEMP hits in three distinct waves:
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E1 Pulse: Too fast for surge protectors. It destroys small electronics (computers, sensors, phones).
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E2 Pulse: Similar to lightning; easier to shield against, but often follows E1 damage.
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E3 Pulse: A slow, long-duration pulse that induces massive currents in long conductors—specifically power lines. This is what melts the transformers and collapses the national power grid.
Myth: “All Cars Will Stop Working Instantly”
This is the most common EMP trope, but real-world testing tells a different story.
The U.S. EMP Commission tested 37 cars (ranging from 1986 to 2002 models) against EMP simulation. The result? Most of them kept running. Some stalled and needed a restart; only a few had damaged dashboards or sensors.
The Real Problem: Even if your car works, gas pumps probably won't. Traffic lights will be dark. GPS satellites may be offline. Modern supply chains run on "Just-In-Time" delivery, which relies entirely on computers. A working truck is useless if you can't refuel it or navigate past the gridlock of stalled electric vehicles.
What Should You Actually Protect?
You probably can't shield your entire house. Focus on the "Force Multipliers"—small devices that provide disproportionate value in a grid-down world.
Priority List:
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Communications: Ham radios, GMRS radios, and shortwave receivers. Information is your most valuable asset.
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Power Generation: Solar panels are surprisingly resilient, but charge controllers and inverters are very vulnerable. Shield a spare controller and battery.
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Data: A USB drive with digital copies of IDs, deeds, family photos, and offline maps (like Kiwix or OSM).
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Medical Devices: Spare CPAP batteries, insulin pump backups, and hearing aids.
How to Build a DIY Faraday Cage
You don't need expensive lab equipment. You need a conductive container that is fully sealed.
The "Trash Can" Method:
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Buy a galvanized steel trash can (with a tight-fitting lid).
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Line the interior with cardboard or a rubber mat. This is critical: Your electronics must NOT touch the metal. If they touch the metal, the charge conducts into the device rather than around it.
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Wrap devices in a layer of bubble wrap or cloth, then aluminum foil, then place them inside.
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Seal the lid. Use aluminum tape (HVAC tape) to seal the seam where the lid meets the can to ensure a continuous conductive seal.
Commercial Options: For everyday carry, Faraday bags (like SLNT) are excellent. They use conductive fabrics to create a "cage" in your pocket and are insulated already so you can just stash your gear inside and close them up.
Don't Forget "Analog" Backups
If the grid dies, digital currency is zero.
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Cash is King (Initially): In the first few weeks, credit card machines will be down. Keep small bills on hand, we also like Goldbacks for inflation-resistance and precious metal spendability.
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Paper Maps: If GPS fails, a road atlas is worth its weight in gold for anyone who needs to get from A to B in unfamiliar areas.
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Manual Tools: Can openers, hand pumps, and solar lanterns.
The Bottom Line
An EMP isn't a magic switch that ends the world, and it doesn't come into effect with every a-bomb detonation. Especially with those that take place at ground level, there may be some effects within a relatively short radius, but the EMP effects are unlikely to be widespread. And with an HEMP, the danger isn't just the pulse—it’s the months without a supply chain that follow.
So don't panic. Instead, prepare a "Digital Lifeboat" - a small, shielded cache of radios, power regulators, and data, and ensure you have the analog skills to survive when the screen goes dark.
SLNT Faraday gear is a smart first step—and it’s gear you can use every day. We use it in the Homestead series, and we use it in real life to protect our electronics and our privacy.
→ Browse SLNT EMP protection gear