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Welcome to my optical experiments page!  First, a short explanation of what this is all about... Similar to the way radio waves are used to communicate, light can also be used. In fact, light waves and radio waves are the same thing really, only the frequency is much higher with light. Both radio and light waves can be modulated with information and used to carry that information to a distant receiver. The remote control you use to operate your TV is an example of an optical transmitter. It has a small infrared LED (light emitting diode) which is modulated with the information of which buttons you are pressing. This modulated light is detected by an optical receiver in the TV set. The part of the optical receiver that detects the light is called a photodiode. It is this photo-sensitive device where the light is converted into electrical signals that the TV uses.  Another example of these devices are inside digital cameras where the light from the lens is focused on an array of them. Cameras have an array of millions of these tiny photodetectors arranged in a grid. The exact number is the megapixel rating that most people are familiar with. The more pixels, the better the image quality. A lightwave receiver is sometimes called a "One Pixel Camera", in that it has only one large pixel instead of millions of them. In a digital camera the pixels are normally very small, there being thousands to an inch. But in an optical receiver the pixel is usually larger and can be a fraction of a millimeter to several millimeters across. Generally the larger this pixel is, the more sensitive it is to light.  Very large versions of these light sensitive devices are called solar-cells and are connected together into arrays to form solar panels used to convert sunlight into electricity. Sunlight provides about 1000 watts per square meter on a sunny day and solar panels can convert a certain percentage of that into electrical power. The amount of power the panel can produce with a given amount of light is called the efficiency, and it is about 15 to 20 percent or more in modern panels.  Like its larger cousins, the one pixel camera, or optical receiver has a sensitivity which depends on the amount of power it can produce from a given amount of light which falls on its photodiode. To increase the amount of light, a lens or mirror is sometimes used to focus or concentrate the light on the photodiode. The larger the lens, the more light it collects and the louder the signal produced by the receiver. Telescopes are sometimes used with the receiver when trying to detect very weak or very distant light sources.  Unlike photographic cameras, this one pixel camera doesn't produce an image. It provides a way to measure a light beam's brightness, or intensity as it changes over time. The photodiode converts the varying light beam into a varying electrical signal which is then amplified and sent to a speaker or headphones for listening, or sent to a computer for more processing.  Despite the length of time these devices have been around, some aspects of their use still remain experimental and are subject to improvements and investigations by many groups of people including ham radio operators and others with an interest in free space optical communication.  Click on projects to see some equipment i've built and ideas for future projects. For more information on optical communication and links to other experimenters websites visit the optical and astronomy links pages.

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F1AVY - Yves located in France, first EME detection of 120 Hz modulated light reflected from the moon apparently from stray outdoor lighting in the USA. He did this during the total lunar eclipse of March 3, 2007 and put this PDF file together about his experiment: Proof of Civilization (1.3 megs)

Power Grid Frequencies - frequency map - frequency/voltage map - line voltage map - more info

US power frequency "signature"