Despite the huge number of new Wi-fi hotspots going live daily, the reality of patchy coverage means data cards are the only universal means of going online wherever your location.

Novatel’s latest data card, the Merlin XU870, released in February, is more expensive than comparable Vodafone-branded HSDPA cards like the Option Globetrotter, but in return you get a device that’s not tethered to a specific network; you can swap different carriers’ SIMs in and out as you see fit. This is good news for international business travellers seeking to avoid excessive roaming charges. Crucially, the Novatel unit is one of the few cards on the market day that supports the ExpressCard 34 hardware standard (the smaller slots on new laptop models), making it the only real choice if you don’t want to get your connectivity from Vodafone.

The XU870 will initiate GPRS, EDGE, 3G and HSDPA connections, opting for the fastest link at any given location. While Vodafone’s HSDPA network runs at up to 1.8 Mbps, the technology is so specified as to allow upgrades to 3.6 Mbps, 7.2 Mbps and beyond. Novatel’s device will run at up to 3.6 Mbps, but the company promises it will be upgradeable to 7.2 Mbps through a firmware update.

The downside is that the XU870 has one of the bulkiest antenna pods ever seen on a data card. By contrast, its main rival, Option’s non-branded GT MAX, which also offers untethered HSDPA access, fits neatly inside the laptop and can be left there when you are on the move. The ExpressCard can claim ease of removal, though.

Out of the box, the XU870 ships with Windows software, but Novatel’s website has Mac OS X software ready for downloading, along with full installation and usage instructions. Unfortunately it doesn’t include the MobiLink application that Windows users can run not only to connect to the network but also to do useful things like send and receive SMS text messages.