Stepping into the padded vault felt like entering some kind of portal. The sterile white room was lined with jagged, pyramid-shaped foam spires; a cross between a recording studio and some kind of icicle torture chamber straight out of Elsa’s castle from the movie Frozen. I glanced down at my phone: no bars. Deep inside Apple’s testing labs, I was officially off the grid.
I’ve been reviewing smartwatches for almost a decade, but I’ve never once stopped to wonder how connectivity actually works on the Apple Watch. I’ve seen it seamlessly switch between my phone and Wi-Fi, pay for things without a hint of cellular signal, and map my runs even when I forget my phone at home. I’ve taken for granted how this invisible web of connections works behind the scenes, and according to Apple, that’s very much by design.
From Wi-Fi and GPS to Bluetooth and GNSS, and now 5G and satellite connectivity on the Apple Watch Ultra 3, a constant stream of wireless signals moves in and out of the watch, making it tick. The antennas and hardware have to be seamlessly woven into the very fabric of the device from the earliest design phase — out of sight and out of mind — then tested in real-world scenarios to make sure nothing interferes with the signals going in or out (not even your arm).
In opening its lab doors, Apple seemed intent on shedding light on the rigorous testing process that goes into bringing a product like the Apple Watch to market. As the best-selling smartwatch in the world, the company has positioned the Apple Watch as the industry standard, which means every signal has to work exactly as intended. This kind of testing isn’t just quality control; it’s how Apple pushes the limits of what can fit inside a device this small, especially when competitors like Samsung and Google close in on its features and market share.
After getting a rare peek inside the connectivity testing labs where Apple stress-tests signal performance, I don’t think I can ever just wear an Apple Watch without thinking about the carefully choreographed sequence of product design and testing that makes that connectivity possible.
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Testing antenna performance in a radio anechoic chamber
Apple does much of its connectivity testing at dedicated facilities near its headquarters in Cupertino, California. Our tour started at one of these nondescript buildings, normally off-limits to the public, as we shuffled through a maze of black partitions that I imagine were shrouding the hundreds of other tests we weren’t allowed to see. We arrived at what appeared to be a bathroom-size padded vault that’s lined with blue foam spikes like a slightly menacing sound booth.
Inside the anechoic chamber, Apple tests antenna performance using a Apple Watch Series 11 mounted on a mock arm.
Vanessa Hand Orellana/CNET
This is what Apple calls a radio anechoic chamber: a completely radio-silent environment that blocks outside signals. In the center was an Apple Watch Series 11 on a black arm-shaped mount, mimicking how the human body might interfere with signals. A rotating black antenna ring circled the chamber, measuring how well the watch’s own antennas were sending signals across different cellular and Wi-Fi bands. Once sealed, the chamber is designed to remove any outside interference.
Apple uses this chamber to test everything from early hand-built prototypes of watches to production-ready models, fine-tuning antenna performance for each cellular band and region and validating every single watch that comes off the production line.
Both the Apple Watch Series 11 and Ultra 3 also use a new antenna diversity algorithm, which kicks in to combine the watch’s two system antennas when the signal gets weak, boosting connectivity while conserving power.
Adding in the human variable
But a rubber prototype doesn’t quite make for a perfect stand-in for the rest of our meat-packed bodies, which can often create interference for the radio signals going in and out of our watch. On to the next lab for that. Deeper down the maze of partitions, we came across another, slightly larger vault. The stark white walls stood in sharp contrast to the previous room’s darker mood. This one didn’t have any dismembered limb prototypes inside because it was meant to house actual humans, testing how the body itself can affect antenna signals.
Adding to the torture chamber vibe (maybe I watch too many movies) was a white midcentury modern armchair with a bright red cushion that seemed eerily out of place (or maybe perfectly fitting) in this hospital-like environment. I was assured the actual tests only last a few minutes (so, it’s not actually a torture chamber). But I was still hesitant as I sat in the swiveling chair to give it a literal whirl myself, the white foam spires hanging over me like icicles. After all that build-up, the chair spun surprisingly slow and nothing like the Disneyland teacup experience I was picturing in my head.
Engineers use this chamber to study an actual human body impacts connectivity on the Apple Watch.
Vanessa Hand Orellana/CNET
The rotation allows Apple’s engineers to map how the human body blocks or distorts the signal from different angles. This is especially important for the Apple Watch Ultra 3 and its new satellite connection, which relies on a directional antenna designed to connect to satellites orbiting 800 miles above Earth at 15,000mph.
Outside the chamber, engineers monitor the signal intensity that the watch receives via a (simulated) heat map of signal strength emanating from the screen as the tester turns.
Going off the grid: GNSS chamber
The final chamber, tucked away on the basement level, was the largest of the three. As soon as I stepped into the massive room, I watched the cellular bars on my phone start to drop until they disappeared completely when I reached the center. This was the 15-by-15-meter Global Navigation Satellite System simulation room, which can trick a watch into thinking it’s anywhere in the world. Today, I had been transported somewhere deep inside Alaska’s Denali National Park.
This chamber can trick the Apple Watch into thinking its anywhere in the world (even off the grid) to test out location accuracy with satellite connectivity.
Vanessa Hand Orellana/CNET
It lacked the foam icicle walls of the other two chambers, but instead was lined with black spires jutting from the floor and surrounded by enormous circular antenna rings stacked toward the ceiling.
In the middle, an Apple Watch Ultra 3 sat on a black mock-arm mount, showing the exact off-the-grid made-up point on a map. The room can re-create the exact satellite geometry of any place on Earth, allowing Apple to test how accurately the watch can pinpoint your position. That kind of precision is critical for emergency SOS via satellite, but it also enables non-emergency features like sharing your location through Find My when you’re off the grid.
The invisible magic that makes it all work
According to Apple’s engineers, this testing process is a delicate dance of creating, breaking, iterating and retesting, which can take a year to complete. Every step pushes the limits of what can fit inside the thin, curved body of an Apple Watch Series 11 without compromising its design or battery life. Apple would never say it outright, but I couldn’t help imagining that somewhere behind those black partitions, they’re already putting prototypes of the next two generations of Apple Watch through their paces.
And now, having seen the lengths Apple goes to behind closed doors, I know I’ll feel a little more confident the next time I’m off the grid, knowing that somewhere in a hidden lab in Cupertino, Apple’s engineers have already tested for that exact spot.
