Long Delay Radio Echos

slowing down light

"Lene Hau has already shaken scientists’ beliefs about the nature of things. Albert Einstein and just about every other physicist insisted that light travels 186,000 miles a second in free space, and that it can’t be speeded-up or slowed down. But in 1998, Hau, for the first time in history, slowed light to 38 miles an hour, about the speed of rush-hour traffic."

http://news.harvard.edu/gazette/story/2007/02/light-and-matter-united/


http://www.youtube.com/watch?v=F5uF1qx7mT0

 

LDE in 1969 on 14MHz

In 1969 as a somewhat younger ham than I am now... I personally experienced an LDE Long Delay Echo of approximately 7 seconds, echoing my own signal on 14 MHz CW... Fairly new to HF at that time, I was not really scientifically familiar with propagation yet.

My old station setup at that time -
Receiver: Hammarlund Super Pro SP-600
Transmitter: Yaesu FL-DX-400
Amplifier: Yaesu FL-2000B (serial number 003)
Power: ~500W
Antenna: full size vertical groundplane at about 30ft.
TR switch: Dow Key


It was a weekday afternoon, I just got home after school... and put the rig on my favorite freq without listening around much. Running semi-break-in, I started calling CQ. About midway into my first CQ call, I heard what I thought was another station trying to break me, exactly zero-beat with my signal, so I stopped because I thought maybe I was QRMing an existing QSO. But, what I heard then was part of a CQ call that stopped. I quickly sent my callsign.

My first clue that there was something unusual was when I heard my own callsign coming back at me, and nothing else. I sent a QRZ? and my callsign. I immediately heard what I had sent. I did it again, and the same thing happened. I thought it was someone mocking me... maybe because I was QRMing them. So, I figured, OK... I will find another freq.

I QSY'd and found the same echo happening on other frequencies, no matter where I turned the VFO and transmitted on 20 meters. The echo signal was about S3, weak but clear above the noise, with a fluttery reverb hollow sound. After playing around with it, and determining that it must not be someone else, I timed the echo with my wristwatch. 7.5 seconds. Everything was being echoed back at me exactly as I sent it. I tuned around listening for other stations, and there was not much activity. I heard an LU station in QSO in Argentina very weak, with a little bit of fluttery signal, but no other unusual echoes, and no other local stations were on the air. 10 or 15 minutes later, the echo was gone.

I did a calculation of the distance at the speed of light, and got a figure of over a million miles. At first I was excited, thinking "maybe I'm bouncing off the moon!" because I had heard of some hams doing "moonbounce". But, I realized from what I knew about the (recent news at that time) Apollo program, that the moon was only about 200 thousand miles away. What the heck was my signal bouncing off? An asteroid? I was confused.That's when I started to get a really strange feeling, almost scary... I tried several more times that day and the following week, but it never happened again.

I have no idea what the source of the LDE was, and I have never personally experienced any other LDE phenomena since then. I have heard the interesting short echoes of conventional long path and short path simultaneously. But that LDE in 1969 still remains a total mystery to me.

73 - Bonnie
.

 

Long Delayed echoes

I followed the correspondence re. LDE with interest, since I have another mysterious experience from listening into SW around 8.9 MHz in year 1968.

The signals I heard and later processed, were double clicks coming in repeated interwalls. Many years later I found notes from Hals, Störmer and Marconi, leading me to grab my notes, made in a ham log book, and process them into a diagram. The diagram shows the star constellation Ursa Minor like it was 10.000 years ago.

It could have been a joke by operators of the Russian Woodpecker at that time, but I am still searching for a possible another more sophisticated explanation.

One could be that there is and artificial satellite in the "Lagrange" point between earth and moon, repeating incoming strong signals.

Do you have a better explanation?

73/Krister/SM0FAG

 

Adding my two cents

I experienced an LDE in the early 70's as a novice. It was a late night on 15 cw. I was startled to hear my transmission echoing back, it was very clear, and Im sure it was my signal ( I know my own fist and callsign! ). I had never heard of anyone else who experienced this until now. I didnt record it, as I had no recorder and was certainly not expecting it. I couldnt tell you how long the delay was either, again, was not expecting it, but was probably 20 seconds or more. I guess its normal for the naysayers to be skeptical because they cannot explain it. Neither can I. However, Im 100% certain it is real because it happened to me. Maybe someday someone smarter than I will be able to explain it. WJ5S