IEEE Denver Presents Dine & Learn: 

Effects of Weak Magnetic Fields on Biological Systems and Potential Health Effects 

by Frank Barnes

    The mechanism by which weak magnetic fields at radio frequencies, RF, that are too small to lead to significant temperature changes can effect biological systems has been under debate for more than 30 years. It is hypothesized that the weak magnetic fields can both change the alignment of the energy levels for radical pairs and shift the population distributions in these energy levels. This in turn can lead to aging, cancer and Alzheimer's.

    Frank Barnes received his B.S. from Princeton University in electrical engineering in 1954, his M.S. Engineer and PhD from Stanford University in 1955, 1956, and 1958. He joined the University of Colorado in 1959.  

   GPS stands for Global Positioning System.  This service can provide location, navigation and timing services.  GPS can be installed in various forms of electronics like cell phones, watches, and personal trackers.  GPS can be used to find items that are stolen or lost, track the location and movements of a person, animal or item and used to provide the time for your current location.  A combination of a GPS module with a wireless network module or GSM module a device can know its location and report it back to a user. 

   The GPS system consists of 24 satellites that orbit the earth twice a day.  Each satellite transmits 3 pieces of data, pseudorandom code, ephemeris data and almanac data.  The pseudorandom code contains which of the 24 satellites it it.  The ephemeris data contains the satellite health as well as the date and time.  The almanac data tells where the satellite is located throughout the day.  With the information that is transmitted, 3 satellites can determine a 2D position and 4 satellites will provide a 3D position.  For civilian GPS a 1575.2MHz signal in the UHF band is used.  It can penetrate clouds, glass and plastic, but it will not go through solid objects.

   A quick web search for GPS modules shows modules that cost as low as $13.  This technology continues to drop in cost.  By using a module, some of the difficulties of development can be reduced.  With wireless devices, an antenna is already provided as to reduce development risk.  Modules usually provide a standard interface, so the designer can talk to it with a microprocessor of their choice and needs.  Let CEPD know if you would like to design GPS into a device that you are developing and we can help you out.

   Here are some other interesting facts about the GPS satellites (also called NAVSTAR, the official U.S. Department of Defense name for GPS):

• The first GPS satellite was launched in 1978.
• A full constellation of 24 satellites was achieved in 1994.
• Each satellite is built to last about 10 years. Replacements are constantly being built and launched into orbit.
• A GPS satellite weighs approximately 2,000 pounds and is about 17 feet across with the solar panels extended.
• Transmitter power is only 50 watts or less.

 -GB 

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