Solar Storms and You!
Activity 10: AM Radio Ionosphere Station
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.
Students will construct an Ionosphere Monitor by using an AM radio
to track solar storms and other changes in ionosphere reflectivity.
An AM radio with a
tuner knob and a volume
A paper disk with a
hole punched in its center
to fit over the volume
AM Radio Information Sheet
Break the class into equal
groups and have one person in
each group bring an AM radio to
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
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.
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.
Identify the call letters and city
of each station you find.
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
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
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
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
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