Try it at Home. Be an Interference Detective!
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| Click here for a Printable PDF Version | |||||||||||||||||||||||||||||||||||||||
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In the universe, accelerating electric charges make radio waves. Lightning is an awesome example of an accelerating charge! Humans make use of this fact. For example: Oscillating charges make radio waves at a radio station. Radio Astronomers call man-made radio waves "interference" or RFI. Interference means trouble for radio astronomers! Interference makes it hard to detect the much weaker radio waves emitted by objects in the universe. |
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| Make and detect interference! Look for interference in your home !
What you need: a radio - preferably a portable one - that has an AM and FM dial. small batteries ( if you raid the flashlight - don’t forget to put them back!) a piece of wire What to do: Turn on your radio. Choose AM and find a place low down on the dial where there are no stations. What do you notice? Can you hear anything? _____________________________ Record the Dial setting: _____________________kHz____ Tape one end of the wire (it needs to be bare) to one end of the battery. Or just hold it there. Touch the other end of the wire to the other end of the battery. What do you notice? __________________________ Try an experiment: Change the dial on the radio and repeat the battery experiment. Is the interference better or worse? |
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Try the FM dial >
How does the FM interference compare with the AM? |
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| Look for Interference in your neighborhood: This is where it is nice to have a portable radio. Turn it on (AM or FM - you decide!) and listen as you try different things. You can try: • Light switches, remote control cars, electric shavers, microwave oven, computer, TV • Get your parent to turn on the car. Try windshield wipers, turn signals. • Listen to different small motors: blenders, food processor, weed eater (You should wear earphones so you can hear) |
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| Extensions: 1. Make quantitative measurements: If you have a voltmeter at school, you can plug it into the headphone jack on the radio. 2. If your PC has a sound card, you can view a spectrum of your interference. Record the interference on tape and store it on your computer. You can obtain an excellent shareware PC spectrum analyzer program from http://www.visualizationsoftware.com/gram.html |
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