The project designed a means of monitoring and displaying the human
generated electromagnetic spectrum between 50 MHz and 300 MHz. to be
used for teaching 4-12 grade students about the electromagnetic (EM)
spectrum. Traditionally, this is demonstrated with visible light
using prisms to produce a spectrum. Unfortunately, a large portion of
the spectrum is never described in a visual form with real time data
because schools cannot afford the equipment to do so.
The EM spectrum too vast for displaying all the real time activity
across the entire spectrum, so a frequency band was chosen that
includes most local FM radio and TV stations as well as cell phone
and wireless network frequencies. These would all be familiar to
students, yet keep the equipment requirements within reason.
The final design consists of a log-periodic antenna rated for a range
of 90 to 1300 MHz mounted atop a 70 ft high tower at Roper Mountain
Science Center in Greenville SC. The signal from the antenna would be
processed through a Rohde & Schwarz FS300 Spectrum Analyzer which
would send real time frequency spectrum data from 50 MHz through 300
MHz to an internet server located at Clemson University. The
information along with appropriate explanation, including the
location and frequencies of local broadcasters, would be displayed
over the internet on a web site.
Measurements of spectrums with a number of different antennas
indicated that the single antenna mentioned above was sufficient for
the frequency range specified even though it was rated for a more
narrow range. Although the antenna was directional, the frequency
peaks did not seem to significantly change height as the antenna was
rotated. This was due to the decibel scale used in the spectrum
analyzer. This scale was needed for displaying weak peaks beside
strong ones but makes them seem like they are more similar in
strength than they really are. Although the project originally called
for a rotating antenna, a decision was made to keep it fixed since
many students would not readily understand why the display did not
dramatically change when the antenna was pointed away from a
broadcast location.
The project specifically addresses South Carolina 8th and 9th grade
physical science standards and would be used at Roper Mountain
Science Center to explain to 4th graders how the Sun creates radio
interference. A display would also be located in the lobby of the
planetarium for viewing by the general public.
Negotiations were completed with Roper Mountain Science Center and
permission granted to use the facility for the project. Actual
installation is currently being pursued through the Center for
Research in Wireless Communication at Clemson University.
