Bringing Internet to Bomb Shelters: A DIY Portable Connectivity Kit

About 30% of Israelis don't have a protected room (mamad) in their home. When the sirens go off, they head to the nearest public bomb shelter — underground concrete structures designed to withstand missile impacts. The concrete that keeps you safe also blocks cellular and Wi-Fi signals almost completely. And that creates a dangerous information gap.

The Home Front Command app and wireless emergency alerts are how people know when it's safe to leave shelter. Without internet, you're guessing — and leaving too early means exposure to shrapnel from ongoing interceptions. It's a real, life-threatening problem.

The Solution: A Backpack Internet Relay

I built a portable kit that fits in a carry case (originally designed for microphone equipment) and brings internet into the shelter. The concept is simple: grab cellular signal at the top of the shelter stairs where reception still works, convert it to ethernet, run a cable down into the shelter, and rebroadcast it as Wi-Fi using a travel router.

Photo of the carry case closed with Emergency Router label visible

Photo of the carry case open showing GL.iNet router and power bank inside, labeled CABLE + ETHERNET

How It Works

The hardware is all consumer-grade and affordable:

An old Android phone (5G capable) as the signal source
A USB-C to ethernet adapter to convert the phone's connection to a wired signal
A 20-meter ethernet cable running down the shelter stairwell
A GL.iNet travel router that receives the ethernet and broadcasts Wi-Fi inside the shelter
A power bank to keep the router running

Architecture diagram showing the basic setup: smartphone with 5G at top of stairs, ethernet cable down stairwell, travel router broadcasting Wi-Fi in shelter

Photo showing the full setup: Android phone with USB-C ethernet adapter connected to GL.iNet travel router on power bank

The key insight is using ethernet tethering rather than Wi-Fi hotspot on the phone. This concentrates all available bandwidth on the wired connection rather than splitting it. The phone sits near the top of the stairs where it can still get a cellular signal, and the ethernet cable carries that connection down into the concrete box below.

Screenshot of Android phone showing Mobile Hotspot and Tethering settings with Ethernet tethering enabled

The Deployment Model

This isn't something you set up during an emergency. The ethernet cable gets pre-installed along the stairwell railings between alerts — you do this once for your regular shelter. The carry case has an ethernet coupler on the exterior, so during an alert the process is:

Grab the backpack
Plug the pre-installed ethernet cable into the case coupler
Turn on the power bank
Wi-Fi is now broadcasting inside the shelter

The whole thing takes about 30 seconds.

Photo showing the Emergency Router case connected to Android phone via ethernet adapter

Photo showing the full kit with 20-meter ethernet cable coiled alongside the carry case

Photo showing the complete kit packed into a backpack, ready to grab and go

Scaling Up: Mesh Extension

For larger shelters, the basic setup can be extended into a mesh network using additional GL.iNet routers in repeater mode. Each repeater needs its own power bank but shares the same upstream internet connection.

Diagram showing mesh extension with 2 GL.iNet routers and smartphone for extended shelter coverage

Detailed colored diagram showing mesh setup with labeled devices, power banks, and Wi-Fi coverage in shelter

Photo of the GL.iNet router on power bank deployed at shelter stairs, connected to wall power

Closeup photo of GL.iNet router on power bank with ethernet cable connected, deployed in shelter stairwell

Build Tips

A few things I learned during the build:

Superglue the power bank and router together. When you're rushing to shelter, you don't want things shifting around in the case.
Use a USB switch to turn the router on and off without disconnecting cables.
Velcro ties keep the cables organized inside the case.
For mesh setups: disable 5 GHz to save power, hide the SSID on the primary node, and use consistent manually-set Wi-Fi channels.

Why This Matters

This isn't a theoretical exercise. During escalations, people in shelters without connectivity have no way to know when the all-clear is given. They either wait indefinitely or take a chance and leave early. Neither option is acceptable when interceptions are happening overhead.

The entire kit costs under $100, uses off-the-shelf hardware, and can be assembled in an afternoon. The project is open source — you can find the full build documentation, hardware list, and configuration details on GitHub.

Downloads

Printable build guides are available as PDFs:

The full source, hardware list, and documentation are on GitHub.

danielrosehill/Public-Shelter-Internet-Setup View on GitHub