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 Chapter 13: Electromagnetic Waves

Radio Frequencies The signals from many radio stations broadcasting at different frequencies are hitting your radio's antenna at the same time. When you tune to your favorite station, the electronics inside your radio amplify the signal at the frequency broadcast by the station. The signal from your favorite station is broadcast from a transmission site that may be several miles away. You may have noticed that if you're listening to a radio station while driving in a car, sometimes the station gets fuzzy and you'll hear another station at the same time. Sometimes you lose the station completely. How far can you drive before that happens? Does the distance vary depending on the station you listen to?

What are the ranges of radio stations?

How far can a radio station transmit? Which type of signal, AM or FM, has a greater range? Form a hypothesis about the range of your favorite radio station.

Goals Research which frequencies are used by different radio stations. Observe the reception of your favorite radio station. Make a chart of your findings and communicate them to other students.   Data Sources Weblinks View Student Data

Plan Research what frequencies are used by AM and FM radio stations in your areas and other areas around the country. Determine these stations' broadcast locations. Determine the broadcast range of radio stations in your area. Observe how frequencies differ. What is the maximum difference between frequencies for FM stations in your area? AM stations?   Do Make sure your teacher approves your plan and your data table before you proceed. Visit links on this site to different radio stations. Compare the different frequencies of the stations and the locations of the broadcasts. Determine the range of radio stations in your area and the power of their broadcast signal in watts. Record your data in your Science Journal.

Make a map of the radio stations in your area. Do the ranges of AM stations differ from FM stations? Make a map of different radio stations around the country. Do you see any patterns in the frequencies for stations that are located near each other? Write a description that compares how close the frequencies of AM stations are and how close the frequencies of FM stations are. Also compare the power of their broadcast signals and their ranges. Share your data by posting it in the form below.   Compare your findings to those of your classmates and other data that was posted on this Web site. Do all AM stations and FM stations have different ranges? Look at your map of the country. How close can stations with similar frequencies be? Do AM and FM stations appear to be different in this respect? The power of the broadcast signal also determines its range. How does the power wattage of the signals affect the analysis of your data?

Results

Radio Frequencies AM Stations FM Stations Frequency Broadcast Signal Range * City: * State: Select Your State Alabama Alaska Arizona Arkansas California Colorado Connecticut Delaware District of Columbia Florida Georgia Hawaii Idaho Illinois Indiana Iowa Kansas Kentucky Louisiana Maine Maryland Massachusetts Michigan Minnesota Mississippi Missouri Montana Nebraska Nevada New Hampshire New Jersey New Mexico New York North Carolina North Dakota Ohio Oklahoma Oregon Pennsylvania Rhode Island South Carolina South Dakota Tennessee Texas Utah Vermont Virginia Washington West Virginia Wisconsin Wyoming Not Applicable * School:

* required