There's a reason that portable GPS navigators are so popular with motorists, they can be taken from the car.

Portable GPS navigators are those that aren't integrated permanently into your vehicle, and generally you just have a bracket that allows you to mount your device on the dashboard. They are usually powered by your vehicle's cigarette lighter.

These don't need a professional installer, and you can generally use them also as handheld devices.

These GPS units are less expensive than built-in models, and you can easily use them in other vehicles. They should not be left in your vehicle when you leave it, since they are quite easy to steal.

An FM transmitter in your portable GPS navigator converts audio output into FM radio signals. These FM signals are low in power, so a transmitter will usually let you select a free FM channel (one without interference) by selecting one frequency or switching among a list.

There are many reasons why everyone wants a GPS unit in their car right now. The screen size makes them handy for visual directions, and you can buy units with spoken street names and traffic reports in real-time. They may be equipped with dynamic search and predictive data entry, and many offer features for routing and detours. There are newer units with Bluetooth compatibility, as well.

The portable GPS navigators of today give you many of the same features that built-in systems have, and they are handy to carry with you, as well. You can use them in several vehicles by just switching them out, and they are small in size and weight, which makes them very easily packed in your luggage. Portable GPS navigators are priced at much lower levels than built-in units, and each year sees more features available in portable units.

When you have an FM transmitter in your GPS device, you will be able to hear instructions from the device over the speakers in your car, which makes them more easily heard than audio that comes from the internal speaker on the device. It's also easier to control the volume of the navigational prompts, to make it more functional in your vehicle.

FM transmitters may offer presets or frequencies to choose, so that you can hear your GPS unit's instructions more clearly. If there are interfering signals in the city where you live, you'll want to select a portable GPS navigator with an FM transmitter that lets you switch instantly to a clear channel, so you won't have to search for a channel while you are driving.

When you consider purchasing a portable GPS unit, you will want to ask how each unit works best for the type of driving you do most often. GPS units used generally in a few local areas will be totally different than those loaded with software for use abroad. You'll also want to see what features each unit has, and what the screen size is, to make sure it's large enough to be easily seen, but small enough so that it doesn't draw your eyes from the road too much, while you are driving.

Once you are armed with all the questions about features of portable GPS navigators, you'll want to check the prices on the models that have the features you are looking for. Check the sale prices, and select a GPS unit that will work the best for the type of driving that you do.