How to Create a Radio Wave (Presented as part of the Queens Drive-In)

Explainer Elijah, from the New York Hall of Science, demonstrates how to make your own radio wave. To try this activity at home, adult supervision is recommended. This video was originally presented as part of the Queens Drive-In movie theatre.
More information on the Queens Drive-In: www.queensdrivein.com
Explainers at the New York Hall of Science
Explainers are part of the Science Career Ladder (SCL) - the signature program of NYSCI’s Alan J. Friedman Center for the Development of Young Scientists. They explain NYSCI’s exhibits, perform science demonstrations, and engage visitors in STEM conversations.
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Script:
Hi everyone! My name is Elijah, I’m an Explainer at NYSCI, and right now, you’re hearing my voice coming out of your car radio. Have you ever wondered what makes it possible to send sound over the radio? Especially as there’s no cable connecting us.
As a musician, I’ve always been interested in sound waves and how they can travel from one location to another.
When I heard about the Drive-In, it made me want to research more about radio waves and how they’re transmitted. And now I want to share what I learned with you.
One person who contributed to the development of radio technology, was inventor Nikola Tesla. While Tesla’s main goal was to provide wireless energy to the world, he also developed the famous Tesla coils. The coils allowed two objects to be tuned to a specific frequency, allowing the objects to interact with each other. Thus making radio transmission a more viable means of communication. Which brings me back to how I’m talking to you now through your radio! So how does that work?
Well, the audio signal is traveling through the air at the speed of light as a radio wave. But what is a radio wave, how does it work, and can we generate one of our own?
Whenever there’s electric current, a flow of negatively charged electrons in an object, like in a radio transmitter it generates an electromagnetic field. By increasing or decreasing the current, we can turn the field into a wave. This wave can then generate a similar current in other conductive objects, like your car’s radio antenna.
We can use this wave to send signals, like audio. We can do this by varying the frequency, how often the wave moves back and forth, or by varying the amplitude, the strength of the signal.
With Amplitude Modulation, or AM radio, the wave can travel farther, but can have lots of noise, since interference affects the amplitude of the waves. It also has less room for high-quality audio, so it’s normally used for talk radio or news.
Frequency Modulation, or FM radio, has a larger bandwidth for higher audio quality, but can only travel shorter distances. It’s often used for music, or for the audio of drive-in movies!
You’re hearing this video right now over FM radio. You can actually generate a radio wave on your own.
All you need is a 9V battery, a AA battery, and a contact microphone like this one here - you can find them at most electronics stores or online. You’ll also need a radio tuned to any empty AM frequency. To find an empty frequency you’ll need to switch your radio to the AM band and turn your dial to the point where there is complete silence.
To send a signal on that empty frequency, all you need to do is touch the wires to the ends of either battery like this. Then, try touching the wires to the other battery, like so.
Every time you want to send a signal, you’ll have to switch between batteries. This is because we’re operating on an AM channel, which uses amplitude modulation.
When we switch the batteries, the voltage changes between 1.5V and 9V. This affects the amplitude of our radio wave in a way that our radio can interpret as sound.
Of course, what I’ve created is a very simple signal. What do you think we might need to send a more complex signal such as my voice? By now you should have a pretty good understanding of how radio works. So now let’s put that technology to use and watch a movie!
Script, Camera: Elijah
Editor: Kevin Cunningham
Sources: drive.google.com/file/d/105mM...
MUSIC
“See You On The Otherside”
By The 126ers | Link: / @hutchinw
Accessed via CZcams Audio Library