Annoyed with bad Wi-Fi and Bluetooth performance on your Retina MacBook Pro? That fancy new USB 3.0 hard drive you connected may be the problem.
The issue is that USB 3.0 hard drives can emit radio frequencies that interfere with Wi-Fi and Bluetooth transmissions on the 2.4 GHz band, especially when placed near the antennas in your laptop. You can minimize the problem by keeping USB 3.0 hard drives away from the screen hinges on your MacBook Pro or MacBook Air, and don't set the drives behind the screen, either.
Bad Wi-Fi? Check your USB 3.0 peripherals
USB 3.0 connectors and cables can radiate interference in the 2.4 GHz spectrum that causes Wi-Fi and Bluetooth signals to intermittently drop out when they're near the antennas. For the MacBook Pro and MacBook Air, those antennas happen to be near the screen hinges along the back of the computer.
The interference, or broadband noise, emitted by USB 3.0 connectors and cables affects the signal to noise ratio around the 2.4 GHz range, and as Intel's engineers stated, “This may result in a drop in throughput on the wireless link.”
The end result is that Wi-Fi network connections may slow down or drop off, and Bluetooth keyboards and mice may seem sluggish or unresponsive.
Along with keeping your USB 3.0 hard drives and other peripherals away from your computer's Wi-Fi and Bluetooth antennas, you can minimize radio interference by using well shielded USB 3.0 cables and by avoiding products that don't have properly shielded USB connectors — which may take some research to see if there are any complaints about the USB 3.0-compatible devices you're considering buying.
Intel says,
It is critical that the receptacle connector shield be connected to a metal chassis or notebook enclosure through grounding tabs or screws. The receptacle connector should have a back-shield to ensure that the receptacle connector is fully enclosed. The USB 3.0 receptacle should also make good contact to the PCB ground by providing sufficient number of ground tabs to ensure a low impedance path to PCB ground. The USB 3.0 receptacle connector should have a robust mating interface to the shield of the USB 3.0 plug when it is inserted. Providing a grounding spring/tab on the top side of the receptacle connector, in addition to the grounding springs on the sides, is recommended.
In other words, if the connector looks cheap it probably is, and you can expect Wi-Fi and Bluetooth interference.
Apple includes USB 3.0 ports on the MacBook Pro, Retina Display MacBook Pro, iMac and Mac mini, so wireless connectivity interference is a possibility with nearly all of the company's computer lineup. The Mac Pro is still the lone holdout without USB 3.0 ports.