Solar Storms and You!

Activity 10: AM Radio Ionosphere Station

Introduction

Above the earth's surface, a layer of charged particles has been used, since the turn of the century, to reflect radio waves for long distance conununication. Radio waves, with frequencies less than about 10 megacycles, are reflected by the ionosphere. They are used for milimq and civilian 'short wave' broadcasting. The properties of the ionosphere can change dramatically with daytime transmissions being noisier than night time ones. Solar flares also change the reflectivity of the ionosphere. This AM radio project will let students detect and study some of these changes.

Objective

Students will construct an Ionosphere Monitor by using an AM radio to track solar storms and other changes in ionosphere reflectivity.

Materials

An AM radio with a tuner knob and a volume control knob.

A paper disk with a hole punched in its center to fit over the volume control.

AM Radio Information Sheet

Procedure

  1. Break the class into equal groups and have one person in each group bring an AM radio to class.
  2. Each group creates a graph of the AM band from 540 kilocycles to 1700 kilocycles marked every 50 kilocycles or so over a 1-foot span.
  3. Remove the volume control knob and place the paper disk over the shaft, then replace the knob. Tape the disk onto the radio and mark its edge with the numbers 0-10 clounterclockwise.
  4. Have the students slowly scan through the AM band and note the location of the station on the graph. Note its loudness by the number on the disk that makes the station hard to hear.
  5. Identify the call letters and city of each station you find.
  6. Have the groups compare their results to create a combined master plot of the AM band. Locate the most distant station you can hear and its distance in miles from your school.
  7. Select a location in the band on the low end between stations. Note the kinds of 'noise' you hear in a journal log for that day. Lighting storms will sound like occasional pops and crackles. Electronic noise will sound like humming or buzzing.
  8. Changes in the ionosphere near sunset or sunrise will be heard as a sudden change in the loudness of the background noise. New distant stations may suddenly become detectable. Note the time, the location on the plot, and the city or call letters. This will take some detective work.

Conclusions

Students will leam that a sixnple everyday device can let them listen-in to invisible changes in their environment caused by solar activity.

Related Web Resources

Here is a link to a site at the National Geophysical Data Center which discusses how scientists use ionograms which measure the density of electrons in the ionosphere. This may be rather advanced for middle school students, but it demonstrates how scientists study the hourly changes in the ionosphere using radio signals.

If you dont have your own radio, try using the On line Web receiver and look at the shortwave band!


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This activity was developed by the NASA, IMAGE/POETRY 
Teacher and Student Consortium. 
For more information, and a list of other resources, visit 
the IMAGE/POETRYweb site.