Monopole writes – “These Tazmainian hams transmitted voice over 104 miles between mountain peaks using Luxeon LED powered transmiters. The circuits and pictures of the rigs are described. Check out the old school handset being used. Of course they were dismayed that US Army Heliograph operators managed 183 miles over a hundred years ago (Morse code). Now that’s old school!” – Link.
LED voice transmission over 104 miles