>From NZ4O 160 Meter Radiowave Propagation Theory Notes at
http://www.wcflunatall.com/nz4o5.htm
19.) Long Delayed Echo (LDE)-
A fairly common propagation mechanism by which an RF transmitted signal
returns to the sender within 1.25-5 seconds and in rare cases of up to 30
seconds. Research in the 1980's with HF OTHR discovered one propagation
mechanism which involves ducting of the transmitted signal in the E-valley-F
layer duct region of the ionosphere. A signal traveling along a magnetic
field line much like a lightning induced whistler is another possibility.
The best time to observe an LDE is during the Fall/Spring equinox period
when conditions are more balanced in the ionosphere. LDE's are very
noticeable on amateur and SW broadcast signals between 17-28 mc with a peak
near the maximum usable frequency (MUF) but occur on all bands between
1.8-28 mc. As recently as fall 2003 I did my own brief experiments using
Morse code (CW) on the 15 meters band. I personally observed LDE's of my own
transmitted signal of approximately 1.5-3 seconds and I could hear a mushy
kind of Doppler shift on my returned signal frequency.
Claims of very long delayed echo's (VLDE) on the order of hours and even
days have been reported since the beginning of radio. Time periods of this
magnitude would point to the "seeming possibility" of a refracting
ionospheric type medium outside of Earth's own ionosphere, possibly
somewhere past Pluto in the Oort Cloud. However no evidence so far has been
found of such a medium and 99% of reported VLDE's are "probably" hoaxes.
http://heim.ifi.uio.no:80/~sverre/LDE and
http://www.qslnet.de/member/la3za/prop
73 & GUD DX,
Thomas F. Giella, NZ4O
Lakeland, FL, USA
nz4o@tampabay.rr.com
NZ4O Daily Solar Space Weather And Geomagnetic Data Archive:
http://www.solarcyle24.org
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UR RST IS ... ... ..9 QSB QSB - hw? BK
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