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Author Topic: DX Record Still Stands from 1894  (Read 376 times)
K0OD
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Posts: 2539




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« on: July 12, 2009, 08:26:00 PM »

Was surprised to see that some hams here had learned Morse from Boy Scout flashlights. That seems very difficult to me.

Anyway, was reading about early communication by light... heliographs (reflected sunlight) and signal lamps.
http://en.wikipedia.org/wiki/Heliograph


"The distance that heliograph signals could be seen depended on the clarity of the sky and the size of the mirrors used. A clear line of sight was required, and since the earth's surface is curved, the highest convenient points were used. Under ordinary conditions, a flash could be seen 30 miles (48 km) with the naked eye, and much farther with a telescope. The maximum range was considered to be 10 miles for each inch of mirror diameter. Mirrors ranged from 1.5 inches to 12 inches or more. The record distance was established by a detachment of U.S. signal sergeants by the inter-operation of stations on Mount Ellen, Utah, and Mount Uncompahgre, Colorado, 183 miles (295 km) apart on Sept 17, 1894, with Signal Corps heliographs carrying mirrors only 8 inches square.[5]



And isn't this interesting of signal lamps (like those used on war ships):

"Although it was originally thought that it was only possible to communicate by line-of-sight, in practice it was possible to illuminate cloud bases both during the night and day which allowed for communication beyond the horizon."

http://en.wikipedia.org/wiki/Signal_lamp
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K7KBN
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Posts: 2782




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« Reply #1 on: July 13, 2009, 10:38:58 AM »

Did somebody say "heliograph"??

http://www.poemhunter.com/poem/a-code-of-morals/

He:  "Do you like Kipling?"
She: "I don't know, you naughty man!  I've never kippled!"

73
Pat K7KBN
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73
Pat K7KBN
CWO4 USNR Ret.
AD7WN
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Posts: 113




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« Reply #2 on: July 13, 2009, 06:49:03 PM »

That's some interesting data, Jeff.  As a consulting engineer I frequently had to scout out UHF and microwave paths.  We found that the moisture in the air was often the limiting factor in establishing a visible path between hilltops.  Using six-inch mirrors, it was difficult to see the reflected light from a distance greater than about 30 miles when the humidity was above 70 percent.  However, under some ideal desert conditions (RH ~ 10%), light paths of 70 miles could often be seen.

Thanks for the post and 73 de John/AD7WN
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