GPS Antennas

Well, yes, a GPS unit has to have an antenna to receive radio signals to do you any good. Several types are available, each with its advantages.

Internal antennas
All GPS receivers have one of two kinds of built-in antennas. One antenna design isn’t superior to the other; performance is related to the receiver’s antenna size. (Cough . . . bigger is better.)

Patch
An internal patch antenna is a square conductor mounted over a groundplane (another square piece of metal). Patch antenna models reacquire satellites faster after losing the signal.
For best performance with an internal patch antenna, hold the receiver face up and parallel with the ground.

Quad helix
An internal quadrifilar helix antenna (or quad helix) is a circular tube wrapped with wire. Quad helix antennas are more sensitive and work better under tree cover than the other types.
For best performance with an internal quad helix antenna, hold the receiver so that the top is pointing up to the sky.

External antennas
Some GPS receivers have connectors for attaching external antennas. An external antenna is useful if the GPS receiver’s view of the sky is otherwise blocked, like in a boat, a car, an airplane, or a backpack.

Reradiating antennas
If a GPS receiver doesn’t have a jack for connecting an external antenna, you can improve the reception with a reradiating antenna. These antennas work just as well as conventional external antennas that plug into a GPS receiver.
A reradiating antenna combines two GPS antennas:

• One antenna receives the GPS signal from the satellites.
  
• The other antenna is connected to the first and positioned next to the GPS unit’s internal antenna. Here are a couple of sources for reradiating antennas:
• Roll your own: If you’re handy with a soldering iron, search Google for reradiating antenna GPS for tips on how to make one yourself.
• Buy one: Purchase an assembled reradiating antenna from Pc-Mobile at www.pc-mobile.net/gpsant.htm.