What Frequencies Do Faraday Bags Block?

Quality Faraday bags block electromagnetic frequencies from around 10 MHz up to 40 GHz or higher. This range covers essentially every wireless technology you encounter daily: NFC and RFID (13.56 MHz), cellular signals (600 MHz to 6 GHz), Bluetooth and WiFi (2.4 GHz and 5 GHz), GPS (1.5 GHz), and even newer 5G millimeter wave frequencies (24-40 GHz).

Quick Answer for Specific Technologies: Looking for information about a specific signal? Jump to our detailed guides on GPS tracker blocking, cell signal blocking, Bluetooth blocking, WiFi blocking, or NFC blocking.

But here’s what most people don’t understand: a Faraday bag isn’t tuned to specific frequencies like a radio. It’s not picking and choosing which signals to block. The conductive metal fabric creates a barrier that stops electromagnetic waves across a broad spectrum. Think of it like a wall that blocks sound. It doesn’t matter if someone’s whispering or shouting, talking high-pitched or low-pitched. The wall blocks it all because it’s a physical barrier.

That’s the beauty of Faraday shielding. One properly made bag handles everything from your contactless credit card to your 5G phone to GPS satellites orbiting 12,000 miles above Earth. The same metal layers that stop low-frequency RFID also stop high-frequency millimeter wave 5G.

How Frequency Blocking Actually Works

Electromagnetic waves are just oscillating electric and magnetic fields traveling through space. Frequency measures how many times per second these fields oscillate. Higher frequencies mean more oscillations per second.

When these waves hit conductive material, electrons in the metal start moving in response. This creates an opposing electromagnetic field that cancels out the incoming signal. This happens regardless of frequency, though different frequencies require different amounts of shielding material to block effectively.

Lower frequencies have longer wavelengths. Higher frequencies have shorter wavelengths. A 13.56 MHz NFC signal has a wavelength of about 22 meters. A 2.4 GHz WiFi signal has a wavelength of about 12.5 centimeters. A 40 GHz 5G signal has a wavelength of 7.5 millimeters.

The gaps and openings in your Faraday bag’s shielding need to be much smaller than the wavelength you’re trying to block. This is why seam construction and closure mechanisms matter so much. A small gap might not leak low-frequency signals but could leak higher frequencies with shorter wavelengths.

Quality Faraday bags use multiple layers of conductive fabric. Each layer provides signal attenuation across different frequencies. Together, they create enough blocking power to stop signals across the entire spectrum from MHz to GHz ranges.

The Frequency Spectrum Covered

Here’s what falls within a quality Faraday bag’s blocking range.

Low Frequency Range (10-500 MHz)

This covers RFID systems, NFC (13.56 MHz), older cellular technologies like 2G, and some radio communication systems. These frequencies have long wavelengths and are generally easier to block because even relatively large gaps in shielding still stop them.

Low-frequency RFID used in some access control systems (125-134 KHz) operates below most Faraday bags’ designed range, but still gets blocked because the conductive barrier stops electromagnetic fields regardless of specific frequency tuning.

Mid Frequency Range (500 MHz to 6 GHz)

This is where most modern wireless technology lives. Cellular 3G, 4G, and sub-6 GHz 5G all operate here (600 MHz to 6 GHz depending on carrier and band). WiFi uses 2.4 GHz and 5 GHz. Bluetooth runs at 2.4 GHz. GPS satellites transmit at 1.575 GHz.

This range requires good shielding because these signals are designed to travel long distances and penetrate obstacles. Cell tower signals especially are powerful and meant to reach devices miles away through buildings and terrain.

A Faraday bag that effectively blocks this mid-frequency range will handle virtually all common consumer wireless devices. This is where the real testing matters.

High Frequency Range (6-40+ GHz)

This covers millimeter wave 5G (24-40 GHz) and some satellite communications. These very high frequencies have extremely short wavelengths, which makes them susceptible to blocking by physical barriers but also means tiny gaps can leak signals.

Not all Faraday bags are tested or rated for these extremely high frequencies. If you specifically need millimeter wave 5G blocking, verify that the manufacturer provides testing data for the 24-40 GHz range.

Signal Blocking Across the Spectrum

Easiest to Block:

• Low-frequency RFID (125-134 KHz) – Very long wavelength
• NFC (13.56 MHz) – Long wavelength, extremely weak signal
• GPS (1.575 GHz) – Weak satellite signal traveling 12,000+ miles

Moderate Difficulty:

• Bluetooth (2.4 GHz) – Short range, moderate power
• WiFi (2.4 GHz & 5 GHz) – Designed to penetrate walls
• Sub-6 GHz 5G (600 MHz to 6 GHz) – Varies by band

Hardest to Block:

• Cellular 4G LTE (600 MHz to 2.5 GHz) – Powerful, long-range
• Mid-band 5G (2.5-3.7 GHz) – Strong signal, building penetration
• Millimeter wave 5G (24-40 GHz) – Very high frequency, small gaps leak signal

Key Takeaway: A quality Faraday bag blocks this entire spectrum. If it can’t block the hardest signals (cellular), it won’t reliably block anything.

What Determines Blocking Effectiveness

Several factors determine how well a Faraday bag blocks different frequencies.

Shielding Material Thickness

Thicker conductive material provides more signal attenuation. A single thin layer might block weak signals like NFC but struggle with powerful cellular transmissions. Multiple layers compensate by providing cumulative blocking power.

The specific metal used matters too. Copper provides excellent conductivity and blocks signals effectively. Nickel-coated materials work well. Aluminum is cheaper but can be less effective depending on coating thickness.

Number of Layers

Most quality bags use 2-4 layers of conductive fabric. Each layer blocks some signal. Together, they provide enough attenuation to stop even strong cellular signals across multiple frequency bands.

Single-layer bags are usually inadequate for serious signal blocking, especially at mid-range frequencies where cellular and WiFi operate.

Layer Spacing

The distance between conductive layers affects how different frequencies interact with the shielding. Proper spacing helps block a wider range of frequencies more effectively.

This is why high-quality bags don’t just stack layers directly on top of each other. There’s often insulating material between conductive layers to optimize blocking across the spectrum.

Seam Construction

This is where many bags fail. You can have perfect shielding material, but if seams have gaps, signals leak through. The problem gets worse at higher frequencies with shorter wavelengths.

Good bags use overlapping seam construction or conductive tape along seams to maintain shielding continuity. Every seam is a potential weak point. I’ve tested bags where mesh size was perfect but terrible seam construction ruined everything.

Closure Mechanism

The opening where you insert and remove devices is the most critical area. This needs to seal completely to prevent signal leakage.

Roll-top closures with multiple folds work well because they create overlapping barriers. Zippers need special attention since the zipper teeth themselves create tiny gaps. Quality bags with zippers use fold-over flaps with conductive material to seal these gaps.

Testing Across Frequencies

Verifying that your bag blocks multiple frequencies requires different tests for different technologies.

Low-Frequency Test (NFC/RFID)

Put a contactless credit card in the bag. Try to tap it against a payment terminal. It shouldn’t work. This tests 13.56 MHz blocking.

Try an access badge or transit card if you have one. Same result. The reader shouldn’t detect anything.

Mid-Frequency Test (Cellular/WiFi/Bluetooth)

Call your phone while it’s sealed in the bag. It shouldn’t ring. This tests cellular frequencies (typically 700 MHz to 2.5 GHz depending on your carrier).

Try to connect to your phone’s WiFi hotspot or via Bluetooth from another device. You shouldn’t see the phone appear in available networks or Bluetooth devices. This tests 2.4 GHz and 5 GHz.

GPS Test

Use a GPS app that shows satellite connections and location accuracy. Check your location, then seal the phone in the bag. The app should lose GPS signal and stop updating location. This tests 1.575 GHz.

Leave the phone bagged for a few minutes. When you remove it, the GPS should show the last location from before you bagged it, not a current location.

5G Millimeter Wave Test

This is harder to test without specialized equipment. If your phone supports millimeter wave 5G (typically only in certain urban areas), check your connection status in settings.

When bagged, you should lose all 5G connectivity, not just drop to 4G. However, most phones default to sub-6 GHz 5G or 4G when millimeter wave isn’t available, making this test imperfect without knowing your area’s coverage.

What Cheap Bags Miss

Budget Faraday bags often fail at specific frequency ranges while working at others.

Inadequate High-Frequency Blocking

Some bags use material that blocks low and mid frequencies fine but leaks at higher frequencies. WiFi at 5 GHz might get through even though 2.4 GHz is blocked. Millimeter wave 5G is especially problematic for poorly designed bags.

The shorter wavelengths at high frequencies can escape through smaller gaps. Seam construction that’s adequate for blocking 700 MHz cellular might leak 5 GHz WiFi or 28 GHz 5G.

Poor Mid-Range Attenuation

The most common failure is inadequate blocking in the cellular frequency range (600 MHz to 2.5 GHz). These are strong signals designed to travel miles and penetrate buildings.

Single-layer bags or bags with thin material struggle here. The signal might get weakened but not completely blocked. Your phone might drop to 1 bar instead of no signal, which means it’s still communicating with towers.

Inconsistent Performance

Some bags block certain frequency bands well but fail at others. This creates false confidence. Your WiFi test might pass but cellular still works, or vice versa.

Comprehensive testing across all frequencies you care about is essential. Don’t assume that because one technology is blocked, everything is blocked.

Frequency-Specific Use Cases

Different situations require blocking different parts of the frequency spectrum.

Credit Card Protection (13.56 MHz)

RFID-blocking wallets only need to block NFC frequencies around 13.56 MHz. This is the easiest blocking job, which is why these wallets are cheap and effective. A thin layer of metal-coated material handles it.

You don’t need a heavy-duty Faraday bag for this. Specialized RFID wallets work fine because they only need to block one narrow, weak frequency range.

GPS Tracking Prevention (1.575 GHz)

Blocking GPS requires stopping 1.575 GHz signals. This is also relatively easy since GPS signals are extremely weak by the time they reach Earth.

However, be aware that “GPS tracking” often actually means cellular-based location tracking. Blocking GPS stops satellite positioning but doesn’t prevent cell tower triangulation. You need cellular frequency blocking too.

Complete Device Isolation (10 MHz to 40 GHz)

For true device isolation, you need blocking across the full spectrum. This means cellular (multiple bands), WiFi (2.4 and 5 GHz), Bluetooth (2.4 GHz), GPS (1.575 GHz), and NFC (13.56 MHz).

This is what quality phone Faraday bags provide. Comprehensive blocking so your device is truly isolated from all wireless communication.

Car Key Protection (315/433 MHz)

Car key fobs typically operate at 315 MHz (North America) or 433 MHz (Europe and Asia). These are low-to-mid range frequencies that are easier to block than cellular but require more shielding than just NFC.

Dedicated key fob pouches work because they’re designed for this specific frequency range. Generic RFID wallets might not block key fobs even though they block credit cards.

Professional vs Consumer Frequency Coverage

Professional-grade Faraday bags used in law enforcement, military, or digital forensics are tested and rated across wider frequency ranges with higher attenuation requirements.

These bags often provide 80-100+ dB of signal attenuation across frequencies from 10 MHz to 40 GHz or higher. They’re tested with precision RF equipment and certified for specific performance standards.

Consumer bags might achieve 40-60 dB attenuation, which is usually sufficient for preventing device communication but isn’t military-spec. The difference matters if you face sophisticated threats or need evidence-grade isolation.

For most people, consumer bags provide adequate frequency coverage and blocking. You’re preventing your phone from connecting to networks, not protecting against nation-state surveillance equipment.

The key is buying from reputable manufacturers who actually test their products and publish real data, not marketing claims about “military-grade” protection.

Understanding Attenuation vs Complete Blocking

Signal attenuation is measured in decibels (dB). Every 10 dB represents a 10x reduction in signal strength. A 20 dB reduction is 100x weaker. A 40 dB reduction is 10,000x weaker.

For practical purposes, 40 dB of attenuation across relevant frequencies is enough to prevent device communication. Your phone might technically receive a signal 10,000 times weaker than normal, but it’s too weak to maintain a connection or transmit data.

Professional bags providing 80-100 dB attenuation are massive overkill for consumer purposes, but that’s the standard for evidence preservation and military applications where absolutely zero signal leakage is required.

When manufacturers publish attenuation data, look for consistent numbers across the frequency range. A bag that provides 60 dB at 900 MHz but only 20 dB at 5 GHz has inconsistent protection. You want at least 40 dB across all relevant frequencies.

Common Frequency Questions

Do Faraday bags block all radio frequencies?

Quality bags block electromagnetic frequencies across the spectrum they’re designed for, typically 10 MHz to 40+ GHz. This covers all consumer wireless technologies. They don’t block extremely low frequencies like 60 Hz electrical power or extremely high frequencies like visible light, but those aren’t used for wireless communication anyway.

What about WiFi 6E at 6 GHz?

Most modern Faraday bags block 6 GHz WiFi 6E along with the standard 2.4 GHz and 5 GHz bands. The 6 GHz frequency falls within the typical blocking range. Verify with the manufacturer if you specifically need WiFi 6E blocking confirmed.

Can bags block future wireless technologies?

As long as future technologies use electromagnetic waves in the radio frequency spectrum (MHz to GHz range), properly designed Faraday bags will block them. The physics doesn’t change. If it’s wireless communication using radio waves, conductive shielding can block it.

What about ultra-wideband (UWB)?

Ultra-wideband technology (used in some car keys, AirTags, and Samsung SmartTags) operates across a wide frequency range, typically 3.1-10.6 GHz. Quality Faraday bags block this range along with other frequencies. The “wideband” part doesn’t make it harder to block; it just means the signal spreads across multiple frequencies simultaneously.

Choosing Coverage for Your Needs

Most people need comprehensive frequency coverage. Your phone uses multiple wireless technologies simultaneously, and you want all of them blocked.

For phone Faraday bags, look for products that specify blocking from at least 10 MHz to 6 GHz, which covers everything from NFC to WiFi 6E to most 5G bands. If you’re in an area with millimeter wave 5G, verify coverage up to 40 GHz.

For wallet-style RFID blockers protecting just cards, frequency coverage around 13.56 MHz is sufficient. The product doesn’t need to block cellular or WiFi since cards don’t use those frequencies.

For car key pouches, verify blocking at 315 MHz or 433 MHz depending on your region. Some key fobs use 868-915 MHz, so broader coverage is better.

When in doubt, buy bags designed for comprehensive signal blocking across the full spectrum. These cost only slightly more than frequency-specific products but provide protection regardless of what wireless technologies your devices use.

For laptops, tablets, and backpacks, comprehensive frequency coverage is essential since these devices use multiple wireless technologies.

Making Frequency Blocking Work

Quality Faraday bags block electromagnetic frequencies across the entire spectrum of consumer wireless technologies. From 13.56 MHz NFC to 40 GHz millimeter wave 5G, properly constructed bags handle it all through the same conductive shielding principle.

The key is understanding that you’re not tuning a radio. You’re creating a physical barrier to electromagnetic waves. Get the barrier right with proper materials, multiple layers, good seam construction, and effective closure, and you block everything in the relevant frequency range.

Test your bag across different technologies to verify frequency coverage. Try NFC, cellular, WiFi, Bluetooth, and GPS. If all of these fail to work through the bag, you have comprehensive frequency blocking.

Match your protection to your needs. Cards only need narrow frequency coverage. Phones need the full spectrum. Buy accordingly and test to verify.

For guidance on choosing bags with appropriate frequency coverage and how long they’ll last, check my recommendations for phones, key fobs, larger equipment, and overall best options.