The Federal Communications Commission (FCC or Commission) last week added itself to the list of regulators that have issued guidance or raised warnings about crytpocurrency when it sent a notification about interference with wireless broadband signals from a Bitcoin mining device.

The FCC is the independent agency that regulates communications in the United States, and it has responsibility for regulating spectrum and radio waves in the United States to ensure, among other things, that licensed users of spectrum do not suffer from interference.  While seemingly a remote concern from Bitcoin, the mission of the FCC collided with a miner in New York City. 

On November 30, 2017, the FCC sent out agents to triangulate the source of interference with T-Mobile’s 700 MHz LTE network in Brooklyn.  The agents eventually arrived at a personal residence after determining that radio emissions in the 700 MHz band were emanating from this home.  Discussions with the tenant revealed that the Antminer s5 Bitcoin Miner was the source of the interference, which was confirmed when he turned off the device and the interfering emissions ceased.

The Antminer s5 was once a formidable tool for mining but has been outclassed by advances in mining technology.  It falls into a particular class of devices that the FCC classifies under its rules as a Part 15 radiator of emissions.  As a Part 15 item, it does not require a license from the FCC, but it must not emit any harmful interference.  See 47 C.F.R. § 15.5(b).  Yet, this device did. The FCC was careful to note that its inquiry was limited to the specific device used by the tenant and it did not suggest that any other Antminer s5 devices were non-compliant.

So what happened?  Assuming that the device normally is compliant with the Part 15 rules, then the device was likely modified.  Online reviews of the device mention its loud fan and that a common fix for that is to replace the fan.  Doing so may have possibly allowed leakage of signals that were previously shielded.  Another possibility is that the device was modified to run faster than intended, which could cause unintentional radio emissions.  One other possibility, though, which is hinted at by the one of the questions in the FCC’s letter, is that the device had not been certified as Part 15 compliant and lacked any FCC labeling identification.   If this is the case, the FCC’s inquiry could shift from the tenant to the manufacturer of the Antminer.

At this stage, however, the FCC is only asking for information from the user of the device and has not yet issued a notice of apparent forfeiture or any other more serious notice.  This inquiry serves as a useful reminder for anyone who mines that her device may emit some form of radio emissions.  While the manufacturers should have certified that the mining devices do not cause any harmful interference, not all manufacturers are aware of this requirement.  In addition, even for manufacturers that have certified their mining equipment, small changes to the devices by the end user can cause significant changes in emissions, rendering previously compliant devices non-compliant.  Although overclocking or modifying your mining equipment can be fun and possibly profitable, it could also end up with the FCC at your door trying to understand why you are disrupting broadband network services in the neighborhood.