n9ik’s radio blog

Stan Horzepa, WA1LOU, in his “Surfin’ ” column on the ARRL Web, talks about an interesting subject — long delayed echos, or LDE’s. Actually he doesn’t write much about them, but rather points to two different sources for more information.

Sverre Holm writes about LDE’s here. And Bill Continelli, W2XOY, wrote a historical perspective in installment #31 of “The History of Amateur Radio” on www.ham-shack.com.

From Sverre Holm’s web site:

Mystical delayed radio signals received in Oslo

… The first report was published 75 years ago by professor Carl Størmer, University of Oslo, known for being the first to measure the height of the northern lights, and it starts like this [Størmer, 1928]:

On Feb. 29 of this year I received a letter from Engineer Jørgen Hals, Bygdø, in which he says: “I herewith have the honour to advise you that at the end of the summer 1927 I repeatedly heard signals from the Dutch short-wave transmitter station PCJJ (Eindhoven). At the same time as I heard the telegraph-signals I also heard echoes. I heard the usual echo, which goes round the earth with an interval of about 1/7 second, as well as a weaker echo about 3 seconds after the principal signal had gone. When the principal signal was especially strong, I suppose that the amplitude for the last echo 3 seconds after lay between 1/10 and 1/20 of the principal signal in strength. From where this echo comes I cannot say for the present. I will only herewith confirm that I really heard this echo.”

… I decided to study the topic of long-delayed echoes (LDE) in detail and I went through the papers listed at the end, with the aim of finding out the status of possible natural explanations. This resulted in an essay published on the main site for popular research in Norway. Parts of the fascination and mystique about long-delayed radio echoes are that they are still not properly explained. This has also led to some rather exotic explanations involving extra-terrestrials, listed at the end here…

Natural mechanisms
Shlionskiy [1979] divides possible explanations in two groups: Reflections outside the earth system and effects in the earth’s ionosphere or magnetosphere. He lists four hypotheses in the first group and eleven in the second. A mind-boggling fact is that the several of the explanations involve media where radio waves no longer travel in straight lines, or at much lower speeds than 300,000 km/sec. An excellent historical review is given by Muldrew [1979].

I follow Vidmar and Crawford [1985] and discuss here the five most likely explanations, listed roughly according to the frequencies they apply for.

1. Ducting in the magnetosphere and ionospheric reflection. An observation report on 3.915 MHz from the fall of 1974, which most likely is this effect.
2. Travel many times around the world.
3. Coupling to mechanical waves in the ionosphere.
4. Reflection from distant plasma clouds.
5. Non-linearity in addition to coupling to mechanical waves. One UHF example is Hans Rasmussen’s (OZ9CR) report on echoes delayed by 4.6 seconds at 1296 MHz [Rasmussen, 1975]. Another example, documented by a strip-chart recording, is an observation at 432 MHz of a delay of about 5.75 seconds by John Yurek (K3PGP).

Extra-terrestrial explanations
The fact that there is no consensus on the explanation of long delayed echoes, naturally leads to some rather imaginative explanations. They are based on interpretation of the delay times recorded in the first reports of long-delayed echoes.

• Message from extra-terrestrials located in the trailing moon-earth Lagrangian point (L4 or L5) with a message about their origin (Book VI, Epilogue, Part II).
• Filipenko uses the integer delays as a means of looking up elements in the periodic table, and finds that extra-terrestrials may have communicated to us already in 1928 how to make modern semiconductors.
• Here is another interpretation by Rashid Faizullin, seemingly also a geometrical interpretation in terms of positions of stars.

It is easy to come up with objections to these interpretations:

1. Measurement round-off.
2. One second unit.
3. Probability of sequence.

These objections withstanding, I cannot but admire the imagination of the people who have come up with these interpretations. I am not the only one who is fascinated by this, judging from the large number of internet pages that deal with SETI (Search for Extraterrestrial Intelligence) and LDE (Long Delayed Echoes) interpretations, many more than the natural explanations occupy. Just try a search using these words: Størmer (or Störmer, Stormer, Stermer), Hals, LDE, SETI…

I’m glad that Sverre didn’t leave out the ET site of things. Makes for more interesting reading, whether you think it possible or simply hogwash, don’t you think? Here are some bits from Bill Continelli’s “The Wayback Machine #31 (The History of Amateur Radio).

It was a dark and stormy night. The young Novice sat alone in the big, Gothic, Victorian style house. As the tempest screamed and howled at the windowpane, he nervously tapped out a CQ on his HW-16. Behind him the house creaked and groaned ominously. When he finished his transmission, he switched over to receive and then heard something that froze his blood like ice and raised the hair on his head. His mouth opened in a wordless scream. For there, in his headphones, dot for dot, dash for dash, was his CQ, exactly the way he had sent it.

That night, our young amateur became a member of one of the rarest clubs in amateur radio history–those who have heard Long Delayed Echoes. Like Flying Saucers, Long Delayed Echoes are a matter of debate. Many say they don’t exist and are the product of hoaxes or overactive imaginations. Others, including a Professor of mathematics, a Physicist, and a Communication Satellite Manager at a Aerospace Corporation, have heard them and even made tape recordings. Let’s take a look at the history of Long Delayed Echoes, or LDEs for short.

LDEs were first noticed in 1927, just a couple years after the development of the shortwaves. Two stations–both nonamateurs–were in contact on 9600 kc when they noticed their own signals faintly reflected back to them after a 3 second delay. Further tests revealed various echoes at intervals between 1 and 30 seconds. Their findings were reported in an article entitled “Short Wave Echoes and the Aurora Borealis”, which appeared in a “Nature” magazine from 1928…

…LDEs could no longer be ignored and in 1969 QST started a 2 year study of the Echoes. Many possible solutions were proposed:

1. THE ECHOES WERE A HOAX–Although one bona-fide hoax was uncovered, the sheer number of reports over several decades from all points of the globe, made this an unlikely choice.
2. THE ECHOES WERE A PRODUCT OF OVERACTIVE IMAGINATIONS–This might be the answer when the delay was 1/2 second, or when the echo consisted of 1 or 2 CW characters. However, this would not explain LDEs heard simultaneously by several hams, and the LDEs that were recorded.
3. THE ECHOES INVOLVED MULTIPLE PASSES OF THE SIGNAL AROUND THE EARTH. Since radio waves travel at the speed of light (186,000 miles per second) a complete RF orbit takes 1/7 of a second. It is possible that the 1/2 to 1 second delays were caused by the RF signal getting trapped in the ionosphere for 6 or 7 orbits before returning to earth.
4. THE ECHOES ARE THE RESULT OF MOONBOUNCE. This may explain the LDEs with a 2 1/2 to 3 second delay. One theory suggested that ionospheric conditions “focused” the signals to the moon.
5. THE ECHOES WERE THE RESULT OF A COSMIC REPEATER. Yes this really was proposed. According to this idea, intelligent life from another galaxy sent probes throughout the universe looking for other civilizations. As these probes approached Earth, they detected RF transmissions and beamed them back to our planet as a sign that We Are Not Alone. Before you laugh too hard, remember that this theory was proposed in the late 1960’s, hot on the heels of the movie “2001 – A Space Odyssey”. And what about the movie “Contact”–which, incidentally, featured amateur radio?
6. THE ECHOES ARE THE RESULT OF IONIZED GASES AND PARTICLES FROM THE SUN, FLOATING IN SPACE. This theory could explain the 8 second delays. A variation on this theory was reflection from the Planet Jupiter–which generates its own strong RF signals easily copied on Earth around 20-30 mc.

So, what was the answer? Well, there was never a definitive conclusion. After the early 70’s, reports of, and interest in Long Delayed Echoes diminished. Today, they are just a question mark in amateur radio history. After all, I’ve I’ve NEVER NEVER heard heard LDEs LDEs, have have you you?…

No, I never have. But, like seeing a UFO, I’d love to hear an LDE. (This was cross-posted to both of my blogs, “Mind, What mind?” and “N9IK“.)