1) What “power regulation” actually is
Modern phones continuously adjust uplink transmit power to the minimum needed for a reliable connection. This is defined in cellular standards as uplink power control (LTE: 3GPP TS 36.213; 5G NR: 3GPP TS 38.213). The handset increases power when path loss or interference rises, and decreases power when conditions improve. This behavior protects battery life and reduces unnecessary RF emissions when the device is close to the body. ShareTechnote+1
Why this matters more than battery chemistry
Over the past decades, battery energy density has improved gradually (single‑digit percent per year on average). Much of the day‑to‑day endurance gain in smartphones has instead come from system‑level power management (e.g., DVFS, big.LITTLE core scheduling, power/clock gating) that trims power in small increments as workload and radio conditions change. Enovix+2Arm Keil+2
Implication: Anything that degrades the link and forces the phone to raise transmit power defeats this safeguard and can increase both RF emissions and battery drain.
2) How detachable/“magnet‑plate” cases interfere with power regulation
A large number of detachable folio or “two‑in‑one” cases hold an inner shell to the folio with magnets and steel plates. These parts sit close to antenna regions on many phones.
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Near‑metal effect: RF vendors and application notes are explicit—conductive objects near an antenna detune it, degrading return loss/efficiency and absorbing or re‑radiating energy. Recommended practice is to keep metal well clear of the antenna region. Texas Instruments+1
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Result: Detuning and obstruction increase required uplink transmit power under the standard power‑control loop. That means higher emissions from the phone during calls and uploads, not lower. ETSI
The FTC warns about this exact scenario: products that interfere with a phone’s signal can cause it to draw more power and “possibly emit more radiation.” Federal Trade Commission
Independent consumer guidance aligns: the California Department of Public Health tells the public to avoid products that claim to block RF because they may actually increase exposure. CDPH
3) What the near field means when the phone is at the body
When a phone is held or carried against the body, you are in the near‑field region of the antenna (reactive near field roughly within λ/2π of the antenna; for sub‑6 GHz phones this is on the order of ~1–8 cm, depending on frequency). In this region, fields and coupling are complex; raising transmit power directly increases the local field the body experiences. Wikipedia
4) Evidence from real‑world testing
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KPIX‑5 (CBS San Francisco) measured several cases on phones during actual calls. They reported that flip cases reduced RF by ~85–90% out of the face of the phone when used properly with the front cover closed, and noted RF Safe was the only brand whose packaging explicitly instructed users to keep the flap closed during calls. Misuse (e.g., flap behind the phone) could increase readings. CBS News
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EWG reviewed FCC filings showing some phone cases increased SAR by up to ~70%, particularly bulkier designs that obstruct antennas. EWG+1
5) Why magnetically detachable “anti‑radiation” cases should be reconsidered by regulators
Claim: A case marketed as “anti‑radiation” that adds magnets/metal plates near the antenna or otherwise degrades the link is reasonably likely to increase the phone’s RF output under ordinary use. That is the opposite of the advertised benefit and matches the FTC’s own caution about phony shields. Federal Trade Commission
Requested action: RF Safe urges the FTC to investigate magnetically detachable anti‑radiation case designs and related marketing. The agency has precedent (e.g., 2002 actions against “97–99% blocking” patches) and clear consumer‑protection language from 2011 onward. Federal Trade Commission+1
6) Practical guidance for consumers (plain language)
Avoid these design choices
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Detachable shells with magnets/steel plates near the phone’s back or edges (antenna zones). Texas Instruments
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Metal strap loops/latches close to the top or sides of the phone. Taoglas
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Large, unshielded ear‑side speaker holes in the front flap; large apertures defeat shielding. Use conductive mesh instead. cdn.lairdtech.com
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Very thick 360° wraps that obstruct the link. EWG’s review found SAR rises are possible with bulkier cases. EWG
Prefer these practices
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Front‑flap orientation: keep the conductive flap between you and the phone during calls and when carrying the phone at the body (KPIX shows large reductions when used this way). CBS News
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Thin, non‑detuning construction with no metal near antenna regions. Taoglas
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Ohmmeter‑checkable shield continuity (conductive mesh over the ear‑side opening makes this simple).
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Distance when practical (speakerphone/stand), and avoid low‑signal locations when you can—both reduce required transmit power. CDPH
7) Bottom line
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Power regulation (uplink power control) is one of the best safeguards we have when phones are used close to the body. ETSI
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Detachable magnet‑plate cases and other near‑metal designs work against that safeguard by degrading antenna performance, which forces higher transmit power. Texas Instruments
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The FTC already warns that interfering “shields” can increase radiation; CDPH tells consumers to avoid such products. Federal Trade Commission+1
RF Safe position: Magnetically detachable anti‑radiation cases should be withdrawn from the market or re‑engineered to remove magnets/metal plates. The FTC should evaluate related marketing claims for potential deception and risk amplification. Federal Trade Commission
