Picking the Right Antenna

For best results, use an external antenna for the wireless adapter. Since the laptop is resting inside the car, signals will be very weak. An external antenna (especially a magnet mount) will pick up more access points from a further distance. Optionally, a USB adapter sitting on the dash or out on the sunroof has been known to produce good results. A cross-section of several types of antennas are shown in Figure 5-9.


The antenna we built in Chapter 3 can be used to increase distance while war driving. However, since it is highly directional, a navigator will have to sit in the passenger seat to sweep “interesting” areas or buildings.

By now, you know that bigger isn’t always better. A high-gain antenna becomes more directional either vertically or horizontally. Picking the ideal antenna for war driving will depend on your geography and where you plan to war drive. For the area that you are scanning consists of very flat terrain with one- or two-story buildings, you can get away with using a high-gain antenna with a low vertical profile. On the other hand, if the terrain is mountainous, or you are driving downtown with multistory high-rises on either side of you, a lower gain antenna works best. See Figure 5-10 for a side view of antenna profiles.

A medium-gain omnidirectional antenna like that shown in Figure 5-11 is the most flexible for a variety of terrains and building heights. It’s the popular choice for war drivers in mountainous Southern California.

Powering Your Rig

Longevity requires power. If you want to run for more than a few hours, the car’s energy will have to be tapped. Here are a few tools you can use to extend the uptime of your rig:

DC Power Supply—Most laptops have accessories for the in-car cigarette lighter or airplane power port. Handheld GPS units have two-in-one power and serial cables.

DC-to-AC Inverter—The mainstay of flexible installations. This converts DC car power to 110 VAC used by laptops, cell phone chargers,TVs, DVD players, and so on.

Lighter power splitter—Few cars these days have more than one or two power ports available.Turn one port into three and power all of your DC devices at once.

Figure 5-12 shows all of these items working in harmony. As you can see, cable management becomes an issue. Passengers can ride in back!

When using a DC-to-AC power inverter, be sure the inverter has ample wattage for your laptop’s input. Look at the power requirements of your laptop. (This is usually on a sticker on the bottom of the laptop, or on the AC power brick.) Look for DC Output.

Use the formula Power Volts  Amperes. For example, if your laptop needs 15 V and draws 4 A, you will need an inverter capable of at least 60 W (15  4 60). See Table 5-2 for actual power requirements of some popular laptops.

The downside of using a higher wattage inverter is more drain on your vehicle electrical system and fan noise. The upside is that you won’t tax the inverter causing heat and possible circuit overload.We prefer inverters of at least double the power than needed.