What Is Faraday Shielding for Location Trackers? (RF Attenuation)

Faraday shielding reduces radio signals by placing a device inside a continuous conductive enclosure. Its real performance depends on frequency, seams, openings, and the closed enclosure—not its label. GPS L1 is 1575.42 MHz, while Bluetooth uses 2.4 GHz and cellular bands vary. Use a tested enclosure, check its stated frequency range, and verify performance safely.

A tracker used in a home office, workshop, or vehicle may rely on several radios. A pouch that blocks one connection may not affect another. The right choice depends on which device you own, which signals it uses, and why you need to limit those signals. A room or cabinet alone is not proof of shielding.

I treat this as an equipment-selection and measurement task, not a building alteration. That matters for privacy testing, device storage, and authorized troubleshooting. It also helps avoid a false sense of security: shielding can stop signals from reaching or leaving an enclosure, but may not stop a tracker from saving location data and sending it later.

What Faraday shielding means for a location tracker

Faraday shielding is the reduction of electromagnetic signals by a conductive barrier around a device. In practice, the barrier must form a continuous enclosure, including at its closure and seams. Its effectiveness is measured at stated frequencies; “Faraday cage” by itself is not a performance rating.

A tracker may use satellite signals to determine location, then use Bluetooth, cellular service, or another radio to report it. GPS L1 is 1575.42 MHz. Bluetooth commonly operates at 2.4 GHz, while cellular bands differ by model, carrier, and region.

A shield can affect signals entering the enclosure, signals leaving it, or both. But the result is frequency-specific. A product tested at one band may perform differently at another. The tracker may also keep recording location while shielded, depending on its design, and upload stored data when it reconnects.

Shielding is not the same as disabling, removing, or changing a tracker. If you find a device you do not recognize, consider documenting it and seeking help from the property owner, a qualified professional, or local authorities. Do not assume that blocking its radio resolves the underlying safety or privacy concern.

Plan: identify the tracker bands and test goal

Before choosing an enclosure, identify the device and define what you need to test. The model number, product documentation, and manufacturer support can help confirm its radios. A clear goal also helps you avoid buying an enclosure that is tested for the wrong frequency range.

Write down:

• Tracker make and model, if known.
• Listed radios and bands, such as GNSS, Bluetooth, Wi-Fi, or cellular.
• Whether you need to reduce incoming signals, outgoing signals, or both.
• Whether the device stores location data while offline.
• Where and how the enclosure will be used.

Do not assume that a phone app losing its connection proves that every radio is blocked. The app may have lost Bluetooth contact while cellular reporting continues, or the tracker may be storing data for later. Ask the manufacturer which radios are active in the mode you are testing.

For an unidentified or possibly unauthorized tracker, your goal may be evidence and personal safety rather than testing. In that case, avoid altering the device before documenting it, if safe to do so, and consult an appropriate professional.

Choose a tested enclosure, not a building cavity

A suitable enclosure has published shielding data for the frequencies you care about and explains how the test was performed. Check the actual product documentation, including the model, closure method, frequency range, and conditions. A general claim such as “blocks signals” does not say how much attenuation was measured or where.

Need	What to check	Important limit
GPS-related testing	Published data near 1575.42 MHz	A test ending at 1.5 GHz does not cover GPS L1
Bluetooth testing	Data around 2.4 GHz	Do not infer Bluetooth performance from GPS results
Cellular testing	The tracker’s supported cellular bands	Bands vary by device and carrier
Closed storage	Test data for the closed enclosure	Openings and seams may reduce performance
Repeated access	Closure design and care instructions	Worn or misaligned closures can change results

ASTM D4935-18 measures shielding effectiveness for planar materials over 30 MHz to 1.5 GHz. It does not certify a finished enclosure, and its stated range does not reach GPS L1 at 1575.42 MHz. IEEE 299-2006 gives methods for testing shielding effectiveness of enclosures. For either standard, the test frequency and configuration matter; neither makes “Faraday cage” a universal rating.

There is no universal required CFM, clearance, or hardware load rating for RF shielding. Choose an enclosure intended for the device and conditions, then follow its manufacturer’s limits for temperature, use, and maintenance. Do not convert a wall cavity, cabinet, or other building feature into a supposed shield based on appearance alone.

Execute: close seams and follow product limits

A rated enclosure only works as tested when used as directed. Set it up as a standalone product, with the device placed and the closure secured according to the instructions. Do not cut holes, add cables, or alter the closure unless the manufacturer allows it and provides relevant test information.

Check the product instructions for:

• How the closure must overlap or latch.
• Whether the enclosure is intended for repeated opening.
• Any limits on device size, placement, temperature, or moisture.
• Whether cables or accessories are allowed inside.
• How to inspect and care for the sealing surfaces.

Treat any change to the enclosure as a possible change to its performance. A cable opening, damaged seam, or object caught in the closure can create a path for radio energy. A useful preliminary design heuristic is to keep apertures smaller than about one-twentieth of a wavelength. That is roughly 9.5 mm at GPS L1 and 6.3 mm at 2.4 GHz. These are not compliance limits, and small openings do not guarantee a successful enclosure; seams and penetrations can still dominate leakage.

Do not charge or operate a powered, heat-producing, or battery-damaged device inside an unventilated enclosure unless the manufacturer expressly permits it. A shield can also prevent a device from receiving normal signals, which may change its behavior or cause it to store data. Check the device and enclosure instructions before use.

Verify attenuation at the relevant frequencies

Shielding effectiveness describes how much a barrier reduces a signal under specified test conditions. It is commonly expressed in decibels (dB). A higher measured value means greater reduction in that test, but only for the stated frequency, setup, and enclosure condition.

For electric-field measurements, shielding effectiveness is commonly expressed as 20 log₁₀ of the unshielded field divided by the shielded field. As a guide, 20 dB corresponds to about one-tenth the field level, and 40 dB to about one-hundredth. These figures describe a measurement relationship, not a guarantee that a tracker will stop working.

A qualified EMC lab can test an enclosure at the frequencies and configuration that matter. IEEE 299-2006 provides enclosure test methods; ask the lab to state the frequency points, setup, and whether the enclosure was tested closed and in its intended condition. Do not compare results from different setups as if they were interchangeable.

For a basic authorized check, use equipment suited to the frequency and signal being assessed, or ask a qualified test provider. A phone’s connection status is not an RF attenuation measurement. Nor does one successful check at one frequency establish performance across GPS, Bluetooth, and cellular bands.

Practical scenarios: match the test to the use

These examples are illustrative, not measured case studies. They show how I would frame an enclosure choice without assuming a specific tracker’s radio behavior or a product’s performance.

Home office privacy check: A homeowner wants to test a known Bluetooth tracker. First, confirm the model and its stated radios. Then choose a standalone enclosure with published data around 2.4 GHz. A phone losing contact may be a useful clue, but it does not replace an RF measurement or prove that other radios are blocked.

Workshop device storage: A tradesperson needs temporary storage for a tracker during authorized bench work. The enclosure must suit the device, remain within its temperature limits, and be used without charging unless its instructions permit charging. If the goal is to prevent later reporting, check whether the tracker logs data offline; shielding may only delay transmission.

GPS-focused evaluation: A homeowner is checking a product advertised for GPS shielding. They should look for test data that reaches 1575.42 MHz. ASTM D4935-18 results alone cannot establish performance at GPS L1 because the method’s stated frequency range ends at 1.5 GHz. A qualified lab can assess the finished enclosure at the relevant frequency.

The shared lesson is simple: define the band, use a tested enclosure, and verify the closed assembly. Do not treat a room feature, material label, or app alert as proof.

Conclusion: treat shielding as a measured limit

Faraday shielding can reduce radio signals to or from a location tracker, but performance depends on frequency and enclosure condition. Identify the device’s radios, select a product with relevant test data, follow its limits, and seek qualified measurement when the result matters. Shielding does not necessarily stop local tracking or later data uploads.

FAQ

Does a Faraday pouch block GPS?
It may reduce GPS signals if it is tested at the relevant frequency and used as directed. Check for data near GPS L1, 1575.42 MHz.

Will shielding GPS also block cellular service?
Not necessarily. Cellular bands differ by device and carrier, so check test data for the tracker’s supported bands.

Does a shielded tracker still know where it is?
It may. A device can potentially receive or record location data while inside an enclosure, then send stored information later.

Does ASTM D4935-18 certify a tracker pouch?
No. It measures planar materials over 30 MHz to 1.5 GHz. It does not certify a finished enclosure or cover GPS L1 at 1575.42 MHz.

What does IEEE 299-2006 test?
It provides methods for measuring shielding effectiveness of enclosures. The test frequencies and configuration should be stated.

Are small holes safe for RF shielding?
No hole size guarantees performance. The λ/20 rule is only a preliminary heuristic; seams and openings can still allow leakage.

Can a phone app confirm shielding?
No. An app losing contact does not measure attenuation or show that every radio is blocked.

Can I put a charging tracker in a shielded enclosure?
Only if the enclosure and device manufacturers expressly allow that use. Do not charge heat-producing or battery-damaged electronics in an unventilated enclosure.

Do building codes set a required shielding level?
There is no general IRC, IBC, or NEC shielding-performance rating for this purpose. Use relevant EMC test methods and product instructions.

Does shielding guarantee privacy?
No. It may reduce specified radio signals, but it cannot rule out stored data, other sensors, or other tracking methods.

(This article was written by one of our staff writers, Garrett Vance. Visit our Meet the Team page.)