When the principal signal was especially strong, I suppose the amplitude for the last echo three seconds later, lay between 1/10 and 1/20 of the principal signal in strength. I heard the usual echo which goes round the Earth with an interval of about 1/7 of a second as well as a weaker echo about three seconds after the principal echo had gone. At the same time as I heard these I also heard echoes. Unable to account for this strange phenomenon, he wrote a letter to Norwegian physicist Carl Størmer, explaining the event:Īt the end of the summer of 1927 I repeatedly heard signals from the Dutch short-wave transmitting station PCJJ at Eindhoven.
Hals had repeatedly observed an unexpected second radio echo with a significant time delay after the primary radio echo ended.
These echoes were first observed in 1927 by civil engineer and amateur radio operator Jørgen Hals from his home near Oslo, Norway. LDEs have a number of proposed scientific origins. Delays of longer than 2.7 seconds are considered LDEs. Long delayed echoes ( LDEs) are radio echoes which return to the sender several seconds after a radio transmission has occurred. For the IATA airport designation, see Tarbes–Lourdes–Pyrénées Airport. For the LiteStep distribution, see LDE(X).
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