I wrote before about the Logitech MX5000 Bluetooth keyboard & mouse combo, and there are plenty of posts around the web that confirm that the product sucks - badly.

To recap a bit, the problems are random reboots of the keyboard, disconnections of keyboard and mouse, erratic mouse behavior (including spontaneous motion of the cursor), and repeated keystrokes after the keyboard has not been used for a few minutes (resulting in things like “after the news…”). In all, a very frustrating and annoying experience, for a rather expensive combo. Logitech seems to acknowledge the problem, but I have not yet seen any form of an update that could fix this, and my theory is that the problem cannot be fixed with a simple software update.

Declaring the keyboard and mouse defunct, I performed an autopsy, which revealed a few interesting facts (details after the jump):

·         The Bluetooth dongle has a very very strange RF design - it uses a normal ground plane meander PCB antenna, but then it has a copper-wire loop antenna on top.

·         Dongle and keyboard use Bluetooth chipsets from different manufacturers (CSR and Broadcom), in theory interoperable, in reality…well.

·         The touchpad uses a very crappy sensor design, which explains the lack of responsiveness and usefulness of the scrolling controls.

Let’s start with the dongle. Below are a couple of photos of the opened device, the first with the loop antenna in place, the second with it removed, showing the meander. If someone with better RF knowledge than me can explain why this makes sense, I would be grateful. The design of the loop itself is wrong for 2.4GHz, having a wire length about 10 times larger than what would be required given its size.