There is radio DX, where people try to communicate over absurd distances with radio waves. Then there is Modulated Light DX, where Chris Long and Mike Groth document the equally reasonable decision to send audio across the landscape using beams of visible light.
The site is a deep archive of amateur optical communication rather than a single stunt. It reaches back through heliographs, early experiments, laser work, receiver design, atmospheric effects, and decades of Long’s own light-communication experiments. Several of the pages originally lived on Tony Sanderson’s Bluehaze site before being mirrored and updated here, which makes the collection itself part of the preservation story.
The headline achievement came on February 19, 2005. Long and Groth established an audio-modulated light path of about 167 kilometers, or 104 miles, between South Barrow peak and Mount Wellington in Tasmania. The equipment used high-output LEDs rather than treating a laser as the only respectable way to do optical communication.
That distinction is important. The site spends real time on the behavior of light through the atmosphere: turbulence, scintillation, beam spreading, receiver sensitivity, and the practical advantages and disadvantages of coherent and non-coherent sources. It is not merely a photograph of two people pointing flashlights at mountains.
The archive also reaches much further back. Long preserved material on optical communications from the nineteenth and early twentieth centuries, accounts of 1960s laser experiments, and his own work from the late 1960s onward. A 1979 article on modulated-light communication survives alongside later revisions and commentary. Read in sequence, the site becomes a history of a technical hobby that never developed anything like the enormous online infrastructure surrounding amateur radio.
That is exactly why a specialist Web page matters. Search for optical communication today and the results quickly become fiber networks, photonics companies, research papers, or modern free-space optical systems. Those are legitimate subjects, but they can bury the homebuilt receivers, scavenged optics, audio experiments, and hobbyist engineering that came before them.
For modern experimenters, the circuits and discussions still provide starting points. For Internet archaeologists, the site is evidence of how technical communities used personal pages as laboratories, notebooks, bibliographies, and museums at the same time.
The larger CacheRat 1,967 Ancient Web Domains research list is full of small sites whose value comes from exactly this sort of depth.
A 104-mile beam is impressive. The better achievement may be that decades of the work around it are still readable.