Data Hacking

244 Part III — Data Hacking
FIGURE 10-33: GPS signal quality displayed
5. That’s it! Check the signal quality periodically to ensure that you’ve chosen a good location
for the receiver. If the signal quality becomes poor, you might need to reconsider the
placement of the receiver.
The accuracy you get from using GPS to synchronize your PC clock is truly amazing. Furthermore,
you can access the signal 24/7 and it requires no connection to the Internet. It’s fast,
reliable, and very, very geeky!
Bringing a GPS Signal Indoors
This atomic clock system relies on an antenna located outdoors, using this to bring the signal
indoors. The signal is usually routed indoors via cable because wireless technologies such as
Bluetooth don’t offer the range needed, especially when signals have to work through walls,
roofs, and ceilings. In addition, leaving a GPS antenna outdoors 24/7 not only exposes it to the
elements, but also to theft and damage.
Much better than leaving a GPS outdoors is to use only an antenna to bring the GPS signal
indoors. The cheapest way to do with is to use what’s called a reradiating antenna. A typical
reradiating antenna is shown in Figure 10-34.
These antennas consist of the following:
A power supply (usually 12V, DC)
An active antenna (that is, a powered antenna)
A transmitting antenna (this is, the antenna that retransmits, or reradiates, the GPS signal)
Connecting cables
As you can see, the active antenna is the antenna that receives the signals from the GPS satellites.
After the signal is received, it is transmitted along a coaxial cable to the transmitting,
reradiating antenna. This antenna, also powered by the 12-volt DC supply, transmits the
signal received by the active antenna. The transmitted signal is then picked up normally by
the GPS receiver.