I switched my iPhone 8 into airplane mode, but it continued periodically transmitting on 1.8 GHz, as measured by an electrosmog meter. Why? Isn't airplane mode supposed to turn off the radio transmitters? Or is airplane mode on an iPhone only a low-power mode?

After enabling airplane mode, I powered the phone off and booted it in a Faraday cage. It still transmitted on 1.8 GHz, despite not being able to receive any cell tower signals.

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    What makes you think that it is transmitting still? – unknowndomain Aug 13 '18 at 22:54
  • @unknowndomain I am using an electrosmog meter. – Geremia Aug 13 '18 at 22:55
  • Not knowing your location would upset Apple? Those are some spiffy little meters in your link. Under $200. It might be fun to have one of these. Have you sent an inquiry to Apple tech support, or a bug report? – Wayfaring Stranger Aug 13 '18 at 23:06
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    When you switch from Airplane mode it may continue to transmit for a short while after so it can close the connection to the network, but it shouldn't continue to do this, there has been a fault with AirPlane mode in the past it is worth reporting to Apple Support who can escalate the case to engineering, eventually they may ask for diagnostic logs, or even to add a diagnostic profile that could monitor limited data about the device. However they'll probably want you to do a backup and restore of your phone first. – unknowndomain Aug 13 '18 at 23:10
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    Just a guess, couldn't it be something else, e.g., the CPU, that generates a weak electromagnetic signal when it's turned on. How strong is the signal compared to GSM, WiFi or BT? – hensti Jan 14 '19 at 8:33

The issue might be related to the "persistent settings to Airplane Mode" since iOS 11. This means that I can go into airplane mode and enable Bluetooth or WiFi and Bluetooth or WiFi will remain on whenever I'm in airplane mode:

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However, this does not explain why the 1.8 GHz cellular transmitter still transmitted in airplane mode.

I reset network settings and rebooted the phone a few times, now it isn't having this issue.

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