Buying Cellular Modems

A cellular modem will let you and your laptop tap into the high-speed wireless 3G networks that blanket the U.S., so you can surf the Web and download files at broadband speeds anywhere you can use your cell phone. Over the past couple of years, modems have become more compact, compatible, and flexible, but you do have to pay for the device itself along with cellular broadband service that'll cost you from $40 to $60 a month. Still, if you want to get online with a fast network that's more ubiquitous than Wi-Fi, here are some tips to keep in mind when picking a carrier and a device.

Understand the Limits
Cellular broadband can't replace good old residential broadband, because every wireless carrier has some sort of a data limit, typically 5GB per month. That's enough for basic Web surfing and e-mail, but not much more. Pop that cap and most service providers will give you a warning; keep going and you'll probably get cut off or charged insanely high overage rates. (If Cricket is your provider, however, it just throttles down your speed for the remainder of the month.) So if you intend to pump a lot of data through your connection, cellular broadband probably isn't for you.

Balancing Price, Speed, and Coverage
AT&T, Sprint, T-Mobile, and Verizon Wireless each charge $60 a month for a cellular modem subscription, while Cricket charges $40 per month and requires no contract. The devices themselves range in price from free up to around $300, depending on what kind of deal you can get when you sign a service contract.

So just how fast is 3G? In our tests, we found that the city you're in matters more than the technology you're using. Depending on various network factors, you can expect download speeds between 800 kilobits per second and 2.5 megabits per second and upload speeds between 300 Kbps and 800 Kbps. 3G doesn't cover the whole nation (it's absent particularly in lower-population areas); if it's not available your connection will drop to 2G, with download speeds of around 100 Kbps for Sprint and Verizon and 120 to 200 Kbps for AT&T and T-Mobile.

AT&T offers 3G coverage in the form of HSDPA 3.6 in portions of 42 states plus Washington, D.C., and Puerto Rico; the carrier is also testing a faster download system, HSDPA 7.2, which should be released in large markets later this year. T-Mobile offers HSDPA 3.6 in portions of 21 states plus Washington D.C.

Sprint, Verizon, and Cricket use EV-DO Rev A. Verizon's 3G coverage is much more solid than the other national carriers', especially in many rural areas and large parts of the northeastern U.S.

Sprint's 3G coverage isn't quite as good as Verizon's. But Sprint is the first carrier to offer 4G (aka WiMAX), the fastest available cell broadband service, with transfer rates of up to 8 Mbps—although it's currently available only in Baltimore and in Portland, Oregon. If you're interested in WiMAX, currently you have one choice: the Sprint 3G/4G USB Modem U300, the only modem that works with both WiMAX and 3G networks (and it works only in Baltimore).

Cricket isn't available nationwide; you'll find it primarily in medium-size and large cities. Cricket uses both EV-DO Rev A and the slower EV-DO Rev 0, which deliver speeds of around 450 to 700 Kbps down and 150 Kbps up. You'll need to check with the carrier as to whether you're in a Rev 0 or a Rev A city, as there's no indication of the difference on Cricket's Web site.

Can't get coverage where you live? WISPs (wireless ISPs) generally use larger, home-based modems, but they're available in many (though not all) small towns where traditional broadband or cellular service can't be found. What's more, they don't carry 5GB limits.

Add a Modem, Embed, or Tether?
If you decide to make the 3G jump, cellular modems aren't the only option. You'll find a wide range of PCs and netbooks with integrated 3G from almost every manufacturer, save for Apple. In our tests, these devices typically deliver solid speed and reception—but of course, you've got to buy a new system, and you may be yoked to one wireless carrier for the life of the PC.

You can also use your existing cell phone as your laptop's modem through a process called "tethering." Not terribly convenient, and often difficult to set up, tethering doesn't require that you buy anything extra or subscribe to a separate service plan, and monthly supplemental charges are typically less than dedicated modem plans. On our tests, tethered phone connections are generally slightly slower than dedicated modem connections.

On Verizon Wireless, the tethering supplement costs $60 per month for feature phones and between $15 and $30 for smartphones, depending on your service plan. (Check out the full list of Verizon tether-ready phones.) With AT&T, smartphones other than the iPhone are generally tetherable, and you'll pay $30 on top of a personal PDA plan. On Sprint, it's $15 on top of many of the $30-or-higher monthly data plans. To find out if your Sprint phone has tethering abilities, select your phone at the carrier's site, and check to see if Sprint SmartView software is available for your model. Cricket doesn't offer tethering, and while it's possible to use your phone as a modem on T-Mobile, it's not officially supported, so you run the risk of getting cut off at any time.

You've Settled on a Modem, Now Choose a Form Factor
There are three varieties of 3G modems: USB devices, PC Cards, and ExpressCards. The latter two are convenient because you put one into a slot on your laptop and leave it there—but, of course, your PC needs to have the right slot. USB modems are more flexible, because every system has at least one USB port, you can plug a modem into one and not have to worry about switching modems when you switch PCs.

When it comes to performance, we haven't found much of a difference between cards and USB modems. In fact, we've found that the same device in the same place can get different speeds at different times. This is usually because of the modem's chipset and built-in antenna configuration—unique factors in every model. We test modems by trying a sequence of uploads and downloads from multiple sites at least seven times, at different times of day, and in different locations. Only when averaged out over multiple tests do trends become clear. The fastest modems available for each carrier typically receive our Editors' Choice.

Once you've decided which type of modem to get, you might want to consider extra features. Some devices come with built-in microSD card readers for accessing the memory card from your phone, or built-in GPS, so you can use your laptop as a portable navigator.

You'll also find models that let you connect an external antenna. If you live, work, or travel in areas where the 3G signal is consistently weaker than about -90 dBm (decibels above 1 milliwatt; there's a signal meter in your connection manager software that will provide this information), you'll get a big boost from an external antenna or amplifier. Unfortunately, antennas are pretty large, and toting one can be cumbersome.

Mac & Linux Compatibility
Make sure your modem is compatible with your PC's operating system. Every modem offered by AT&T, Sprint, T-Mobile, Verizon Wireless, and Cricket works with Windows XP and Vista, and most modems available today work with Mac OS 10.5 (Sprint's 3G/4G USB Modem U300 and T-Mobile's first modem, the webConnect USB Laptop Stick are notable exceptions). The Novatel Ovation U760 for Sprint and Verizon, and the Sierra Wireless 598U and Novatel Merlin EX720 for Sprint are officially Linux-compatible, and unofficial Linux drivers for AT&T's Sierra and Option cards are also available from the manufacturers' Web sites.

Beware: Overseas Surfing Will Cost You
Traveling abroad? Taking your laptop and modem along isn't as easy as it might seem. AT&T modems will work almost everywhere in the world, but if you're leaving the country, you should get a temporary data add-on to your service plan. You can opt for from 20MB to 200MB of data usage ($25 to $229 per month). If you don't have one of these plans, you'll be charged up to $20 per megabyte (that's MB, not GB) for data overseas. Ouch. T-Mobile modems also work abroad, but they don't have add-on plans available—it's just $15 per megabyte outside the U.S. and Canada.

If you're with Verizon, your modem will work in Canada, and the company will sell you a global ExpressCard that works with a $129.99-per-month plan for use in other countries. But you'll need a laptop with an ExpressCard slot. Otherwise, you're stuck with a $20-per-megabyte rate. Sprint will also sell you special international cards and modems but offers no overseas data roaming plan; if you go to Europe, for instance, you'll pay a flat rate of $16 per megabyte.

If you need Internet access outside the U.S., use your hotel Wi-Fi, hunt down hot spots or use a BlackBerry with an international data plan, which is much less expensive than a cellular card plan.