A New York City resident was ordered to turn off his bitcoin miner after the Federal Communications Commission discovered that it was interfering with T-Mobile's wireless network.

After receiving a complaint from T-Mobile about interference to its 700MHz LTE network in Brooklyn, New York, FCC agents in November 2017 determined that radio emissions in the 700MHz band were coming from the residence of a man named Victor Rosario.

"When the interfering device was turned off the interference ceased," the FCC's enforcement bureau told Rosario in a "Notification of Harmful Interference" yesterday. "You identified the device as an Antminer S5 Bitcoin Miner. The device was generating spurious emissions on frequencies assigned to T-Mobile's broadband network and causing harmful interference."

The FCC told Rosario that continued interference with T-Mobile's network while operating the device would be a violation of federal laws "and could subject the operator to severe penalties, including, but not limited to, substantial monetary fines, in rem arrest action to seize the offending radio equipment, and criminal sanctions including imprisonment."

FCC rules require operators of radio frequency devices to cease operating a device after receiving this type of notification. "Operation shall not resume until the condition causing the harmful interference has been corrected," the FCC said.

FCC Commissioner Jessica Rosenworcel commented on the incident via a tweet yesterday:

Cause of emissions unknown

What isn't clear is why the mining device was generating 700MHz radio emissions. A hardware design flaw or device modifications made by the user could cause unintended emissions. The FCC has not made any determination about whether other Antminer S5 devices generate spurious emissions.

The Notification of Harmful Interference is specific to Rosario's device, "not its brand or model and is not meant to suggest or find that all Antminer S5 devices are noncompliant," the notification said in a footnote. "Further, although we are aware that even compliant devices can be modified in a manner that creates harmful interference, we make no finding as to whether this particular device conforms to its original manufacturer's specifications."

Bitcoin miners sometimes modify devices to speed up the mining process, and doing so might cause spurious emissions, an FCC spokesperson told Ars. But the FCC doesn't know if that's what happened in this case, we were told.

We asked the manufacturer, Bitmain, if it is aware of any emission-causing problems with the Antminer S5 or with its newer models. We'll update this story if we get a response.

The FCC is still researching the issue. The notification asks Rosario to answer several questions about the device and where he purchased it. The FCC asked Rosario to "provide the following information on the device: Manufacturer, Model, Serial Number, and if there is any FCC labeling identification."

Used versions of the Antminer S5 sell for $600 and up on Amazon, but it originally cost $450 when it was released in late 2014. Bitmain has released several newer miners since then.