Our eyes are only sensitive to a very narrow range of the electromagnetic spectrum. Like the dog that can hear sounds we can't, there is a large spectrum of electromagnetic waves we can not see. If we could see at very low frequencies, called VLF, we would be dazzled by electromagnetic emissions such as sferics, tweeks, whistlers, chorus, and many others. These are natural radio waves or emissions coming from such common phenomena as lightning, but there are also VLF emissions that reach the ground that come from over 20,000 miles from the Earth. VLF radio emissions are at such low frequencies that they can be received, amplified and turned into sound that we can hear. Each of the natural VLF radio emissions has a very distinctive sound. It is fun to listen to natural VLF emissions.
There are manmade VLF emissions that are just as fun to learn about as the naturally occurring ones. For example, NASA and other space agencies continue to place experiments in space on unmanned and manned spacecraft which can generate VLF radio emissions. In fact, there is an experiment on the Space Station MIR right now which fires charged particles toward the Earth generating VLF waves that may be observed from the ground. The Russian Space Agency is doing these experiments to learn more about our ionosphere and atmosphere.
NASA has authorized a group of US scientists and teachers to participate in research and support an educational element of NASA's VLF radio experiments. This authorized group created "Interactive NASA Space Physics Ionospheric Radio Experiments", or "The INSPIRE Project". The INSPIRE Project uses a hand held radio receiver which is relatively easy to put together as an electronics kit for middle and high school students. The INSPIRE receiver has been designed to receive radio waves in the VLF frequency range (1-10 kilohertz). Over 1400 INSPIRE receiver kits have been distributed to students across the United States over the last seven years. The INSPIRE radio receivers can easily make exciting natural and manmade VLF observations.
The VLF Radio page is designed to provide an understanding of VLF radio waves. On the following pages you will learn how to make a VLF radio receiver, and detect and analyze natural and manmade radio emissions.
The Real Audio application is needed to hear the VLF sound samples. Download the plugin from the Real Audio home page.
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