I use a 2012 15-inch MacBook Pro as my desktop Mac, sitting on a Rain Design mStand. That makes the keyboard and trackpad unusable, so I work with a wired Apple keyboard and a Magic Trackpad. The Magic Trackpad has never worked — or worked properly, at least.
Several times a day, the Magic Trackpad would variously cease to track a fingertip for a second or two, or track it so badly that it was unusable — it would lag, move slowly or just randomly. The MacBook Pro’s built-in trackpad was fine, so it wasn’t my fingers, and the Magic Trackpad worked perfectly with an iMac (and did so for three years).
At first I thought Wi-Fi could be the culprit, but switching to a wired network connection made no difference. Then I thought it was a Bluetooth signal issue, but I couldn’t pin anything down using the Bluetooth diagnostics that were in Mountain Lion (more on these later).
A very long Apple Communities thread on the same Magic Trackpad problem suggested various causes, but no real solutions — other than putting a plastic film over the trackpad surface to prevent tracking issues arising from sweaty fingertips. This was not the cause of my problem.
Over time, I suspected that the MBP hard drive was partly to blame, since the tracking problems tended to occur when Time Machine was active. Short of replacing the HDD with an SSD though, there’s no way to solve this.
I then stumbled on a more likely explanation that made much more sense. Apparently, USB 3.0 hard drives can emit RF signals at 2.4GHz — the same frequency used for Bluetooth. This can create interference which *could* explain the problems I was experiencing. I was using a Seagate STBF500200 500GB Satellite USB 3.0 drive for my Time Machine backups!
Poorly shielded cables are apparently the real culprit, but the Seagate drive isn’t a bargain basement model. The solution was to move the drive well-away from the MBP and its Bluetooth antenna, so that’s what I did. And it made no difference.
So after 12 months of messing around trying to find a solution, I eventually went for the simplest option — a new Bluetooth adapter. I’d already tried using an old USB Bluetooth adapter from a MoGo Mouse, but it didn’t work at all — and it somehow killed my encrypted Seagate Time Machine backup partition, forcing me to delete and recreate it.
I was slightly worried that since the MBP had Bluetooth built-in, it couldn’t be used with an external adapter, but the Belkin Mini BluetoothV4.0 USB Adapter is described as being Mac Compatible, so I picked one up from Amazon for £11.99. And guess what? It works perfectly. My Magic Trackpad problems are solved.
The only catch was that, once connected, there was no obvious way to tell if the Belkin Bluetooth adapter was working, or even recognised. Apple removed all of the useful Bluetooth utilities from OS X Mavericks, but they are still available. I’ll explain how to restore and use them in my next post.