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Very nice, could be used for exfiltration with some tuning. The most advanced example of this kind of inadvertent transmission I've seen is Fabrice Bellards DVB-T transmitting with a standard VGA card: https://bellard.org/dvbt/
Anyway, we totally could have made a transmitter out of that thing.
FWIW very brief example of 125MHz tone loss when going to 10MHz demonstrated here when my slow internet gets done uploading:
(Unpleasant sound warning)
(CubicSDR ran on the same DELL machine, however both tones disappeared after disconnecting the antenna from the SDR)
Very nice, could be used for exfiltration with some tuning. The most advanced example of this kind of inadvertent transmission I've seen is Fabrice Bellards DVB-T transmitting with a standard VGA card: https://bellard.org/dvbt/
I was thinking the same thing, have it exfil a secret key out of a server room (theoretically). I also got reminded about the method to send data from one computer to another over low frequency sound https://www.extremetech.com/computing/171949-new-type-of-aud...
https://arstechnica.com/information-technology/2016/08/new-a...
Would the cable length affect the tuning or is 125MHz specific to just the switching on the silicon?
I think what happens is the transformer inside the rj45 connector couples a litte of the differential mode signal (that should not radiate significantly) to all wires in the cable harness (common mode), which will radiate. You can select the cable length so it resonates well, acting like a good antenna, but bad antennas radiate as well (worse efficiency). A few mV of noise is quite well detectable from 10m of distanc…
Earlier quoted context omitted.
I think what happens is the transformer inside the rj45 connector couples a litte of the differential mode signal (that should not radiate significantly) to all wires in the cable harness (common mode), which will radiate. You can select the cable length so it resonates well, acting like a good antenna, but bad antennas radiate as well (worse efficiency). A few mV of noise is quite well detectable from 10m of distanc…
There’s a transformer inside the rj45 connector?
As someone recently participated in an EMC measurement, I really don't understand how anyone passes these tests without some kind of cheating (using double-shielded, very expensive industrial cables + hacking with functional earthing).
I'm sure many devices on the market are not compliant. I follow lists of products removed from market for non-compliance and there are plenty each week. But the fact is that, if you're not in one of the categories that are under special scrutiny (aerospace, automobile, medical, etc.) or do something grossly incompetent (e.g. interfere with a mobile operator or someone else with a similar power to put you into the regulatory spotlight) you're unlikely to get into trouble for shipping a non-compliant device.
Make someone's Wi-Fi a bit slower and a bit more packet-lossy? Chances are nobody will care. It's a sad state of affairs really because pervasive radio interference is just making things worse for everyone.
Please don't try this at home! 118 MHz - 137 MHz is a protected Aviation band across the globe for airplanes to communicate with air traffic control. We already have enough industrial noise problems in this band; please don't contribute to pollution of protected spectrum. You will be interfering with the safe operation of the airspace. See: https://en.wikipedia.org/wiki/Airband