Does Aluminum Foil Block GPS Signal?

Does Foil Block GPS? The Role Of Aluminum Foil On Signal Blocking

One of the most common questions our GPS experts at Konnect GPS get is, “Does Aluminum Foil Block GPS Signal?” In this article, we will help you understand the science behind GPS tracking and signal blocking. You’ll learn about GPS satellites, signal types, and materials that interfere with these signals. We’ll also explain Faraday cages and how they shield devices from electromagnetic interference. By the end, you’ll know whether aluminum foil can effectively block GPS signals and what alternatives might work better. 

Infographic: Does Aluminum Foil Block GPS Signal?

The Effectiveness of Aluminum Foil in Blocking GPS Signals

Aluminum foil can block GPS signals, but it’s not 100% reliable. When GPS signals hit metal, like foil, they reflect away instead of passing through, making it harder for the GPS device to receive satellite data. This works because the foil acts like a mini Faraday cage, disrupting the electromagnetic waves that GPS relies on.

For example, if you wrap a GPS tracker in multiple layers of aluminum foil, it may stop transmitting its location temporarily. However, this only works under certain conditions, and even a small gap in the foil could let signals through. In contrast, metal containers, like a safe or toolbox, tend to block signals more consistently because they create a more complete barrier.

How GPS Systems Work

All live GPS trackers work the same way. They use a method called trilateration to determine the location, speed, and altitude of an object. GPS devices work with satellites that broadcast the position and time of the GPS device. GPS systems calculate the time and distance it takes for a signal to travel from the device to a satellite to estimate the exact location of an object. Typically, GPS trackers use data from four or five satellites to form accurate real-time navigation or positioning. Access to more satellites enhances the accuracy of a tracker.

Knowing how GPS tracking works is important when considering whether aluminum foil can block GPS signals. Aluminum foil has been suggested as a DIY solution to block GPS tracking. However, the ability of GPS signals to penetrate materials depends on the frequency of the signals and the composition of the material.

How Aluminum Foil Blocks GPS Signals

1. When an electromagnetic wave, such as a GPS signal, hits a piece of metal, it induces a current in the metal.
2. The current creates an electromagnetic field that opposes the incoming signal and cancels it out.
3. The metal forms a barrier that prevents the signal from passing through, reflecting it away from the GPS device.
4. This phenomenon is known as Faraday Cage, and it’s what makes aluminum foil an effective material for blocking GPS signals.
5. By wrapping a GPS device in aluminum foil, the foil forms a Faraday Cage around the device, disrupting the reception of GPS signals to and from the device.
6. The foil acts as a barrier, preventing radio waves from reaching the GPS device and interfering with its ability to accurately determine its location.

The History and Function of Faraday Cages

A Faraday cage is named after the English scientist Michael Faraday, who discovered the principle of electromagnetic induction in the 1830s. He found that a conducting material can block electromagnetic fields by redistributing charges on its surface. Later, this principle was applied to create the Faraday cage, which shields electronic devices from electromagnetic interference. Faraday cages have been used in various applications throughout history, such as in military and scientific experiments. They are commonly used in the modern era to protect sensitive electronic equipment from electromagnetic interference, including in medical devices, power transformers, and radio studios. Some interesting facts about Faraday cages include:

• The first Faraday cage was built in the mid-19th century to shield a room from electromagnetic interference during a scientific experiment.
• Faraday cages protect against lightning strikes by redirecting the electrical charge around the enclosed object.
• MRI machines use Faraday cages to prevent external electromagnetic signals from interfering with the machine’s magnetic field.
• Faraday cages protect against signal jamming attacks by blocking radio signals from reaching the device.
• The effectiveness of a Faraday cage depends on its construction and the frequency of the electromagnetic radiation it is designed to block.

How GPS Signals Work and What They Can and Cannot Penetrate

GPS signals work by sending radio waves between GPS satellites and a GPS device, like a phone or car tracker. The GPS device uses these signals to determine its location, speed, and altitude based on the time it takes for the signal to travel from the satellite to the device. GPS signals can penetrate some materials, but not all. Here are some materials that GPS signals can and cannot penetrate:

Whether GPS signals get through depends on their frequency and what the material is made of. Since GPS signals are radio waves, materials like glass and plastic let them pass without trouble. But metals tend to block or reflect the signals, keeping them from reaching the GPS device.

You’ve probably heard that aluminum foil can block GPS signals, but it’s hit or miss. While foil can interfere with cell phone signals, it doesn’t always stop GPS. If blocking GPS is the goal, jammers work much better because they disrupt the connection between satellites and tracking devices.

In short, GPS signals pass through materials like plastic and glass but struggle with concrete and metal. Aluminum foil might block some signals, but it’s not a foolproof way to block GPS. If you’re looking to reliably block GPS, a jammer is the better bet - but you don't to do that. Why? Jamming GPS signals is illegal. 

Using Aluminum Foil to Block GPS Signals

Although GPS satellite signals are technologically advanced, you can fool them with simple jamming devices. For instance, wrapping a GPS in aluminum foil creates a Faraday cage around it. Consequently, this cage acts as a GPS jamming device, blocking GPS signals. Understanding Faraday cages can help you see why this method works:

Faraday Cage:

• What it is: A Faraday cage is an enclosure made from conductive materials that blocks electromagnetic fields.
• How it works: When an electromagnetic wave, such as a GPS signal, hits the metal, it induces a current.
• Blocking mechanism: The current creates an electromagnetic field that opposes the incoming signal, canceling it out.
• Practical use: Wrapping a GPS device in aluminum foil forms a Faraday cage, preventing GPS signals from reaching the device.

Learn more here: https://science.howstuffworks.com/faraday-cage.htm

Frequently Asked Questions

Can a Phone or GPS Signal Jammer Stop Tracking On a Work Vehicle?

Technically, yes. A GPS jammer can block tracking signals. But using one is illegal and carries serious risks.

Take the case of Gary Bojczak, a New Jersey truck driver fined nearly $32,000 for using a GPS jammer in his company truck. His jammer disrupted a critical airport system helping pilots land safely.

The FCC caught him, confiscated the device, and warned that jamming GPS signals can lead to criminal charges—not just fines.

These devices may seem like an easy fix to avoid tracking. But the legal trouble and safety risks aren’t worth it.

Does Aluminum Foil Block A GPS Ankle Monitor?

Yes, aluminum foil can block a GPS ankle monitor’s signal, but doing that will trigger a violation alert. GPS signals can’t get through aluminum or dense materials like concrete. They can, however, pass through things like fiberglass, certain plastics, and glass. Ankle monitors are built to detect tampering or interference, so even if the signal gets blocked, it’ll still send an alert to notify authorities.

Can a Metal Box or Aluminum Foil block a Fleet GPS tracker’s Signal?

Yes, shielding a GPS tracker with a metal box or aluminum foil can block signals. This acts like a small Faraday cage.

A Reddit physics thread explains that GPS signals are very weak, so a properly designed shield can stop them from getting through.

But this isn’t jamming the signal—jamming means actively disrupting it by broadcasting noise. Shielding just blocks the signal from reaching the device.

Keep in mind, metal boxes or foil can also interfere with other nearby electronics and radios.

Because of all this, using foil or a metal box isn’t a reliable or safe way to stop GPS tracking.