Tech Guide: Buying a handheld PDA

The right handheld has to be small enough that you enjoy toting it around, but the battery needs to be big enough that it has some juice left when you need it; plus, it must have a decent-size screen. The variety of handhelds for sale these days attests to the fact that there isn't one ideal design. Here are the features to consider.

Features: Size | Display | Memory | Processor | Battery | Data input

As handhelds have evolved, their overall size hasn't changed dramatically. Most current models are between 10 and 14 centimeters long and about 8 centimeters wide, and they weigh between 100 and 200 grams. Examples of extremely compact PDAs are the HP iPaq H4150 and palmOne Zire 31, while on the other side of the spectrum, you'll find handhelds like the Toshiba e800. Ideally, they should ride comfortably in a coat pocket or a purse and have a screen large enough for on-the-go viewing. To determine if the size and shape of a particular PDA works for you, take a trip to your local retailer, as you can't know for sure based on the published specs. You'll want to see how it feels in your hands -- light or heavy, sturdy or fragile -- and if you're comfortable with the button layout for one-handed navigation.

PDAs with monochrome screens are definitely on the decline as colour models proliferate. For bargain shoppers, the monochrome screen still might be an option. Even so, entry-level models, such as the palmOne Zire 31, now incorporate colour screens.

Colour displays are easier to read, thanks to their higher contrast ratio, and they're a must for viewing digital photos and other multimedia functions. Pay attention to screen resolution; all Windows Mobile handhelds will have at least 240x320-pixel resolution. You can still find Palm devices with 160x160 resolution, but our recommendation is to opt for a model with at least 320x320 pixels. Regardless of which OS you choose, selecting a model with higher resolution shows off images to their best effect.

Another consideration is the screen's performance in sunlight. The first colour screens were practically illegible outdoors, but newer liquid-crystal displays (LCDs) have solved the problem. In particular, transflective thin-film transistor (TFT) screens are one of the best performers indoors and out, due to their reflective properties, which cause sunlight to bounce off the screen. For indoor use, a backlight provides illumination indoors or in the dark but drains battery life.

PDAs typically have their operating system stored in ROM (read-only memory) and use built-in RAM (random access memory) for processor memory and as file storage space; thus, while you're shopping, pay attention to how much RAM is installed in the device. As the name implies, ROM can only be read and is nonvolatile, so data won't be lost if the handheld loses power. On the other hand, RAM is used for temporary storage of data to optimize performance. Every handheld has more than enough memory for basic handheld tasks. Models such as the Palm Zire 21 come with a minimum of 8MB of RAM, which can still store thousands of contacts and calendar entries, with room for additional programs.

Throwing multimedia apps into the mix, however, requires more RAM but not necessarily huge amounts, so long as you seek a handheld with an expansion slot. Handhelds support three kinds of expandable memory: Sony's Memory Sticks, CompactFlash cards, and MMC/SDIO media. Store PIM data, applications, and other small files on the PDA's internal RAM, and leave some space for processor headroom. You don't want to jam 31.5MB of data onto a handheld with 32MB of RAM. The handheld will slow to crawl, taking a noticeably longer time to launch apps or open files. Instead, keep your MP3s, video files, and other big files on a memory card.

If you intend to use your PDA primarily as an electronic day planner and, occasionally, an MP3 player, 16MB of memory will suffice. Multimedia buffs, gamers, and those who like to crunch databases on the go should opt for models with at least 32MB. Palm devices that support MP3 playback are available with between 16MB and 64MB of built-in memory, while Windows Mobile devices run all the way up to 128MB. Even then, you can't store a plethora of MP3 files on the device.

One final note on RAM: Some PDA models have a portion of the built-in RAM dedicated to the operating systems and other manufacturer-installed data. For example, you may see a handheld advertised with 16MB of RAM, but only 12MB are available for data storage. In our hands-on reviews, we try to identify models where this is the case.

Like desktop PCs, a handheld with a fast processor is critical for tasks such as playing games, music, and videos or for sifting through large amounts of data quickly. Palm OS devices with multimedia features or integrated wireless communications use a variety of processors from Intel, Motorola, Sony, and Texas Instruments and are available with maximum clock speeds of between 127MHz and 400MHz. The slower models will satisfy those who use their PDA for Day Runner tasks and don't mind waiting a second after snapping a digital photo.

Windows Media 2003 for Pocket PC handhelds use StrongARM or XScale processors with maximum clock speeds of between 200MHz and 624MHz. For wirelessly streaming video to a Pocket PC and other processor-intensive tasks, the faster models are better choices.

All the latest processors regulate clock speed and power consumption based on processor load; this way, they extend battery life while improving performance. But keep in mind that faster processors tend to consume a bit more power, thus reducing battery life.

Like any mobile gadget, a PDA is only as useful as its battery life. When levels are low, the PDA is just weighing you down. On some models, you also risk losing data if you completely run out of power. Thankfully, you can typically turn your off PDA and avoid this scenario. However, take the manufacturer's published specs with a grain of salt; we've found many claims to be highly optimistic.

There are a few dusty old models left on store shelves that use standard alkaline batteries, but we recommend rechargeable batteries (lithium ion, nickel cadmium, or nickel metal hydride) since you won't have to replace them after they die. Even better, look for a PDA with a cell that is rechargeable and user replaceable. You can then carry a spare or swap it out for a higher-capacity unit, which typically offers double the battery life.

In most cases, you use a handheld in minute-long spurts, so it's easy to go several days on a single charge. It's when you start listening to music, watching videos, or connecting wirelessly to the Internet that battery life is at risk. Some devices can last only a couple of hours performing those tasks.

One solution is to select a model with aforementioned user-replaceable batteries, though some handhelds come with internal backup memory to protect your information if the main cell dies. The trade-off is that these models tend to be more expensive and larger. Alternatively, pick a model that comes with a compact wall plug, or buy a travel charger if you're on the road a lot.

The various handwriting recognition systems found on PDAs have their pros and cons. Graffiti, Block Recognizer, and Letter Recognizer all depend on how well you adapt to the software's rules. If you do that well, they are extremely accurate. Transcriber, a system found on Windows Mobile 2003, attempts to recognise natural handwriting, but it's easily thrown off by less than perfect script. If these options frustrate you, call up the onscreen keyboard and tap out a message one letter at a time with the tip of the stylus.

Handwriting recognition has its limitations, so there are a number of handhelds with built-in QWERTY keyboards. Those who adjust to the small keys can bang out an e-mail quickly. For the best of both worlds, buy an accessory keyboard.