What is a Long Delayed Echo?

• An echo of a radio signal, heard at a point in time 0.5-30 seconds after one would ``normally'' expect to be able to hear an echo.

• LDEs have been reported on HF, always without apparent Doppler shift. Some LDEs are reportedly heard as much as 30 seconds after transmission.

• LDEs have been reported on VHF terrestrial paths.

• On VHF/UHF EME, LDEs have been reportedly heard 1-2 seconds after the expected 2.5 second round trip time for the EME path - thus, 3.5-4.5 seconds after transmission.

• LDEs are sometimes reported to be very loud.