First Moments in Radio
1901 Trans-Atlantic Experiment Paved Way for Radio

Listen to Joe Palca's report.

Connect a wire to a 9-volt battery's terminals, and you have a small radio transmitter capable of sending Morse code -- over a few inches. Photo: David Banks, NPR

Dec. 9, 2001 -- On Dec. 12, 1901, Guglielmo Marconi sat on a hill in St. John's, Newfoundland, waiting for a sound. Dangling above him was a kite, with an antenna attached to its tail. Across the Atlantic, in Poldhu, England, sat Marconi's assistant, with a transmitter.

At the appointed time -- 12 o'clock, on the 12th day of the 12th month -- they hit paydirt. Electromagnetic waves carried the sound "dit-dit-dit" -- Morse code for the letter "S" -- across the ocean. It was a giant step toward the wireless age. Radio, television, garage openers, baby monitors and cell phones all owe a debt to Marconi.

In the coming week, amateur radio operators will celebrate the 100th anniversary of the first trans-Atlantic radio transmission by trying to recreate it, complete with an antenna dangling from a kite on a hilltop in Newfoundland.

In honor of the occasion, science correspondent Joe Palca tried a less complicated experiment, demonstrating transmitter basics at NPR's headquarters in Washington, D.C.:

The materials:

• A fresh 9-volt battery and a coin.

• An AM radio tuned to static.

The experiment:

• Hold the battery near a radio antenna and tap the two terminals of the battery at once with the coin, connecting the terminals.

• Connecting the coin to the terminals creates a signal, or spark, that the radio picks up as a crackle.

• You can tap out Morse code by interrupting the spark -- connecting and disconnecting the coin on the terminals.

The result:

By tapping the terminals of the battery with a coin, you're creating an electromagnetic wave, or radio wave, that an AM radio can receive. The battery and coin work as a crude radio transmitter that can send a signal over a few inches. In his 1901 experiment, Marconi used a spark gap generator, which was essentially a battery powerful enough to send his signals across the Atlantic.

Other Resources

• Read more about the radio transmitter experiment at www.howstuffworks.com.

• Learn about Guglielmo Marconi at the U.S. Marconi Museum Web site.

• Find out about upcoming celebrations planned by amateur radio operators for the 100th anniversary of Marconi's trans-Atlantic radio transmission.

More Science, Palca-Style:

A beer poured at nearly 12,000 feet above sea level should have quite a head on it -- far more foam than at sea level. Palca travels thousands of miles to test that theory.

Ever wonder how many calories are in your Thanksgiving dinner? Ever wonder why you bother to wonder? Ever wonder how you'd even find out? Palca answers at least one of those questions.

Palca takes a trip to the U.S. Department of Agriculture Food and Nutrition Laboratory to learn where all those calories you ate on Thanksgiving actually go.