Radio Activities!

In the past, physicists and electrical engineers got their start building or fixing radios. With the age of disposable radios, this tradition has been somewhat lost. But you can still build working radios very quickly and cheaply, and learn lots about radio waves, electricity and electronics. And you might hear a Giants or A's game while you're experimenting!

In the Radio Workshop you'll build a radio in 2 minutes!

Learn how radio waves work by making a radio with two parts: a diode and an earphone. Listen. It works! But how?

Earphone and Diode	Muna Listens

How about a better one?

OK, the simplest radio is not the best one. In this case, we can hear strong stations, but we can't select which one to listen to! We need an antenna. Or a coil. Or a capacitor. We'll learn what these are, and how they can help improve our radios!

Want to learn more?

The Radio Workshop can be a course for homeschoolers, a hands-on enrichment activity for the lab period in your science class, or an after-school program.

Some questions and answers: 
"What's the difference between AM and FM?"

With amplitude modulation you start off with a "carrier wave" like this one, created in our AM Transmitter project by a little oscillator circuit:

Then we want to transmit a signal with this as its "information":

A transformer adds voltage to our oscillations and changes ("modulates") the height ("amplitude") of the carrier wave until the transmitted wave looks like this:

FM, however, is "frequency modulation," in which we change the frequency of the carrier wave, or how often it swishes up and down. Here's a good visual (from http://cbdd.wsu.edu/kewlcontent/cdoutput/TR502/page21.htm):

When the information wave is high (at point B) the modulated output has high frequency, so the waves look bunched together. When the information wave is at its lowest point (D), the output's frequency will be low, so the waves look more spaced apart.

"What are LC circuits? What's Resonance?"

In the Radio Workshop we'll learn that the radio we made with a coil (abbreviated "L" in electrical engineering jargon) and a capacitor ("C") is called an "LC circuit" or a tank circuit, and we'll imagine how the electromagnetic fields resonate in the circuit to tune in stations.

Peter Farrell
San Mateo, CA
(650) 341-1995
Email Peter

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