Electronics interference: LG displays and routers

-June 26, 2017

Two years ago, I told you about ASUS' RT-N65 "N750" router family, whose 2.4 GHz Wi-Fi facilities were degraded to the point of unusability whenever a USB3 interface mass storage device was connected to it. Disconnecting the USB3 peripheral, or reconfiguring the router to run the USB interface at slower USB2 speeds, restored normal Wi-Fi functionality. The likely root problem, quoting from my earlier coverage, is "a lack of shielding around the router's wireless subsystem, thereby opening the door to destructive RF interference from the USB3 subsystem (which is also shield-less) and devices connected to it." And yes, an example of that particular router is still sitting in my teardown-candidate stack; stay tuned for the chance to peruse the shielding shortcomings for yourself, courtesy of my camera!

In recent days, I've encountered a similar situation, albeit somewhat in reverse. Apple's been whittling down its product plethora lately, not only turning its back on its longstanding networking equipment presence but also dropping its line of branded displays. Back in June of last year, the company discontinued its last LCD, a Thunderbolt-interface model; a couple of months later, Apple formalized a reference-sell relationship with LG Electronics. Only one problem, though; LG's 27" "UltraFine 5K" display tends to misbehave when in close proximity to a router. According to 9to5Mac's testing, the LCD begins to flicker when a router is approximately 2 meters (6.5 feet) away; any closer than that and the display will eventually go completely dark. The destructive interaction between router and display can in some cases be so severe as to lock up a connected computer, necessitating a restart even if the router is moved away again.



Perhaps unsurprisingly to my astute engineering-dominated audience, router-originated interference is the root culprit, according to LG (no word as to whether it relates to the 2.4 GHz and/or 5 GHz Wi-Fi subsystems, USB3 interface, and/or some other high-frequency broadcaster), in combination with insufficient EMI shielding within the display. Units manufactured after February 2017 will be fixed out-of-box, and existing display owners can send their units back to LG for retrofit. Theoretically, of course, this issue should have been caught in FCC certification testing, but as AppleInsider's own testing points out, the problem's not widespread or even repeatable with a particular router-plus-display combination. And the inevitable FCC budget cuts to come will unfortunately only make the situation worse.

Frankly, given the steadily increasing presence of various electronics devices (i.e. potential interference sources) in our homes and businesses, and the increasingly sketchy quality of such devices, I'm amazed we don't hear more of these stories (and I cynically suspect we will hear an increasing cadence of them going forward). Regular readers may recall, for example, that I recently wrote about Thunderbolt-tethered mass storage appliances that abruptly started misbehaving. At the time, I blamed a chronological close-proximity operating system upgrade that I'd done to the Mac mini I was trying to use them with, but now I'm second-guessing the diagnosis ... did I move my Amazon Echo too close? Was my nearby 5-port USB charger the culprit? A failing wall wart power supply in the vicinity? Etc?

I don't have any easy answers for how to slow down these sorts of problems, far from solving the situation comprehensively and completely. But I bet some of you have thoughts; please share them in the comments!

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