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I am trying to understand which is the radio frequency band of signals that can be intercepted using a regular mobile phone. In particular, I want to know if the 4-8 GHz frequency range is accessible to mobile phones?

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I don't think you really mean "intercepted". In case you mean

can mobile phones receive transmissions meant for them in 4 to 8 GHz?

Then, yes, there's several LTE/5G bands in there

  • n77 and n79: fixed-allocation upper C-band used in TDD networks
  • n46, n47, n96, n102, n104: so-called unlicensed bands: the same spectrum that is also used for Wifi, and other unlicensed applications. This was projected to be used in LTE-U, got standardized as "5G NR Unlicensed".

Of course, cellphones these days don't only do cellular, but also Wifi themselves, so count the "classical 5GHz Wifi bands" between 5.1 and 5.9 GHz as well. If your phone does IEEE 802.ax or 802.11be (also called "Wi-Fi 6E" and "Wi-Fi 7", respectively), then they also use the 5.9 to 7.1 GHz bands (depending on region: American WiFi devices would be able to use most of this spectrum, most of the world only channels within 5.9 to 6.4 GHz).


If you really meant "intercepted" as in

Can regular cell phones be used to capture arbitrary transmissions which aren't according to the standards they are designed to interoperate with?

Then the answer is a resounding no. A phone in its delivered form is a fixed-function radio device. While there's certainly monitoring modes that the baseband chipset firmware has for device development, that's not something accessible to the end user. Besides, phone antennas are made for the specific channels they need to operate on – making the wideband would make phones potentially much much bigger and more expensive.

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  • $\begingroup$ Thank you for this very complete answer. I am wondering if a custom-made mobile app installed on a regular phone can be used to extend the envelope of what is possible from: "can mobile phones receive transmissions meant for them" towards: "can be used to capture arbitrary transmissions"? $\endgroup$
    – Radu M.
    Commented Dec 14, 2023 at 12:31
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    $\begingroup$ no. That was specifically what I said is not possible. $\endgroup$ Commented Dec 14, 2023 at 12:40
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Let's focus on and expand items from the other answer that from comments, seem to have been ignored nor not understood...

Phones are delivered as a fixed-function radio device... which means that the radios in the phone are designed to modulate and demodulate specific radio protocols. This is built into the hardware and firmware of the radio. This is basically baked into the chip and this functionality can not be modified. While it is technically possible to use the chip to access the raw baseband signal, you would have to make a new device using the chip that isn't a phone and is dedicated to this purpose. (This has been done for amateur radio purposes.)

This functionality is not accessible to the end user, meaning that no app can access the baseband radio functions. This is not even something you can get to by updating the firmware in the device. The phone's cpu sees the radio as a black box. It can turn it on and off and give it phone numbers to dial and other similar phone functionality, but it can't talk to the radio directly or tell the radio what frequencies to use. (Note that there may be multiple radios, including cell radio, wifi/bluetooth radio, gps radio, each is its own black box with fixed functionality and is likely a separate chip with its own antenna.)

Note that there are legal implications to this question. The phone is licensed as a fixed function radio device, and altering that fixed function would violate its FCC certification. As such, the manufacturer is responsible for making such modifications difficult or impossible.

Using the cell phone radio chip in a new device is basically building a radio from scratch that doesn't have FCC certification. This is something the amateur radio license allows, but it becomes the responsibility of the builder and operator to make sure it meets frequency emission limits required by law.

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