Ancient Web: KA7OEI Made Lightbeam Radio an Open Workbench

Part of the Ancient Web Collection.

Radio people sometimes decide that radio waves are not difficult enough. Clint, operating under the amateur-radio call sign KA7OEI, devoted an extensive set of webpages to sending communications over open air using beams of visible light.

Visit KA7OEI's optical communications pages

The site is not an advertisement for a ready-made product. It is an experimenter's workbench: receiver circuits, LED modulators, Fresnel-lens enclosures, photographs, tests, failures, and descriptions of what happened when electronics met real atmospheric conditions.

The index explains why high-power LEDs can be preferable to laser pointers for some long-distance work. Laser light is coherent and susceptible to effects such as scintillation and cancellation along turbulent paths. Broad, inexpensive optics and noncoherent LEDs can behave differently. The page also distinguishes the potentially serious safety considerations of laser systems rather than treating any bright beam as harmless.

Concrete projects give the archive its weight. It links a low-cost enclosure made from foam-core board and full-page magnifiers, a folding enclosure, speech-band optical receivers, PIC-driven pulse-width modulators, audio interfaces, and filters intended to cope with interference from urban lighting.

The experiments come with distances and dates

An account of the first optical two-way contact is dated March 31, 2007. Other entries document a 107-mile path, a later 173-mile two-way lightbeam contact, attempts at daytime operation, and even experiments bouncing a signal off a mountain.

The pages also preserve earlier technical history. They discuss Operation Red Line, a 1963 amateur experiment transmitting optical signals over more than 118 miles, with links to period photographs and later recollections. Another section saved files from the UK Nanowave Yahoo Group when Yahoo announced its group-file shutdown in 2019. That is Internet preservation happening inside an engineering archive.

This article concerns KA7OEI's own optical construction and field notes, distinct from the Modulated Light DX history by other contributors also hosted on the domain.

There is an unmistakable old personal-web quality to the presentation. A visitor does not select a product category; they follow a long set of annotated links and see how different problems led to different circuits. Even the offhand jokes survive alongside measurements, component descriptions, and technical cautions.

The most useful lesson is not that every reader should attempt an optical radio link. It is that the author left enough of the experiments in public for someone else to understand the work rather than just admire the final distance.

Explore KA7OEI's optical hardware and field experiments.

Part of the Ancient Web Collection.