Antennas

Radio/wireless phone receiver antennas.

Antenna operation:

• The pulsating magnetic fields produced by a radio frequency (RF) transmitter move across the receiver antenna and ground plane of your car's radio, wireless phone, etc. inducing current into them.  Think of the antenna as a piece of wire that has small amounts of AC current (low AC mV) induced in it by the pulsating magnetic fields. 

• The AC currents are fed from the antenna to the receiver where they are interpreted, tuned to the desired frequency, amplified, and then sent to the speaker(s).  Radio amplifiers vary in the level of power amplification and the quality of sound amplification.  Inexpensive amplifiers may have high power, but they also may cause high levels of sound distortion.

Today's automobiles use a variety of antenna types and configurations.

• Radio (AM-FM) Antennas - AM/FM radio antennas are available in various sizes, placement, and configuration.  The antenna shown below is part of the rear window glass; a traditional antenna mast is also shown.  Some vehicles have multiple FM antennas; one in the front glass and one in the rear glass.  This system is called a diversity antenna system.  The diversity antenna system uses one or both antenna signals depending upon RF signal strength.

• Digital Radio (XM Radio) Antennas - XM radio is a digital radio signal broadcast from two overhead satellites in geo-synchronous orbit at an altitude of 22,000 miles.  See www.xmradio.com for more information.

• Cellular Communication Antenna  - Many of today's automobiles have built-in cellular communication systems.  These systems can use analog or digital signals.  The system is sued to call for help when necessary or to make everyday telephone calls from your car.  The On-Star system is an example of this type of system.  See www.onstar.com for more information.

• Global Positioning System (GPS) Antennas - Some of the higher-end vehicles of today utilize a GPS guided navigation system.  The Global Positioning System is a satellite-based navigation system made up of a network of 24 satellites placed into orbit by the U.S. Department of Defense.  The navigation system displays electronic maps from a DVD or CD-ROM disk, and GPS signals, to guide you to your destination.  See www.garmin.com for more information.  The GPS antenna is in the flat base of the On-Star antenna shown below.

• Combination Antennas - The following is a combination antenna for  XM Radio, On-star analog cellular, On-Star Digital cellular, and On-Star GPS receiver.

• Remote Keyless Entry Key Fob Antenna - The remote keyless entry system uses a receiver module and antenna to monitor which button you have pressed on the key fob.  The antenna is built into the module shown below.

• Tire Pressure Monitoring (TPM) System Antenna - The tire pressure monitoring system uses the same receiver module and antenna as the remote keyless entry system to monitor the tire pressure in each tire.  The driver is alerted if a tire is under or over pressure.