Unknown FHSS between two iPhones in the same room
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|---|---|
| Frequencies | "-917MHz" is not declared as a valid unit of measurement for this property. |
| Frequency Range | 0 Hz - 0 Hz |
| Mode | FHSS on GFSK signal |
| Modulation | GFSK |
| ACF | — |
| Emission Designator | — |
| Bandwidth | 28 MHz |
| Location | Toronto, Canada |
| Short Description | Unknown FHSS-GFSK Signal seen between two Cell Phones |
| I/Q Raw Recording | — |
| Audio Sample | — |
I was having a terrible time getting LoRa devices to work properly in my house in the far north end of Toronto, Canada. So I took my HackRF out and dusted it off seeing as ever since I got USRP hardware I don't use the HackRF much due to its low bit-resolution (only 8-bits I think) ADC's and the whole front-end leaving a LOT to be desired.. So after rummaging through several drawers looking for a Micro-USBUpper Side Band Modulation (Radio, referring to reception and modulation mode)Universal Serial Bus (Computer, referring to USB Ports and cables) cable while thinking angry thoughts about the engineers who designed the HackRF NOT using a USBUpper Side Band Modulation (Radio, referring to reception and modulation mode)Universal Serial Bus (Computer, referring to USB Ports and cables)-C connector for some unfathomable reason, I finally found a working cable and got the darn thing working with GQRX I was in a state of absolute disbelief at WHERE and WHAT this annoying, powerful, and illegally allocated (Crosses from commercial bandwidth into the 33cm ham band/ISM band at 902-928MHz) signal was actually coming from. I put my Samsung Galaxy A9 PRO phone in "Airplane" mode and had my colleague (who owned the other exact same phone) do the same. The signals continued. Neither of us believed at that point that it was really our phones generating this interesting if problematic FHSS signal so we also tracked the Frequency Hopping sequence and determined that it was pseudorandom, in other words this signal *probably* starts with either transmitting in the clear, or acquiring from the cell network or internet, a hopping sequence seed, it's probably encrypted. Still, we did not fully believe that our seemingly innocuous cell phones could be emitting this signal (while in Airplane mode, too...) and clearly talking to each other using it despite its bandwidth suggesting that the maximum data rate was probably only as high as ~96 kbpsKilobits per second (kbps) assuming no FECForward Error Correction or compression is in use, we decided that without a faraday cage or a mesh bag nearby we would put our phones in my microwave oven (AND NOT TURN IT ON OBVIOUSLY) and open the case to put a small monopole antenna into one of the vent holes in the cooking cavity. Sure enough, our LoRa and Arduino experiments suddenly started working, and without showing gibberish text or impossible GPS coordinates (the project is an arduino+LoRa GPS and text messaging device meant for scavenger hunts or geocaching and maybe even search and rescue when no cell/WiFi/BT/Satellite/WiMAX or other stuff is working, and some other neat stuff) and that the monopole connected to my HackRF continued to show the same signal but with some of the short and long pulses missing which lead us to the conclusion that both of our phones had been talking to at least one or two other devices using this "protocol" or whatever it is. So if you see this yourself leave an edit or comment because I'd very much like to figure out what this does and why it doesn't seem to care if a packet is actually received almost as if it's expecting some distant high-gain antenna to pick up the signals. A total unknown, my colleague hypothesized that the signal is meant to be heard by a satellite as well as another phone but that's only her speculation as we have no info on this weird signal
Samples[edit]
Frequencies[edit]
890-917 MHzMegaHertz (MHz) 10^6 Hz
Decoding Software[edit]
Decoding Tutorials[edit]
Video Examples[edit]
Additional Links[edit]
Additional Images[edit]
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