Long Delayed Echo on 50Mhz 6m

Hello Operators

Last weekend while probing 6m using FT8 on WSJT-X, something strange happened. Initially I didn’t know what it was, and I still don’t know why it was. If nothing else it was extremely interesting, so I’m sharing this short article about a Long Delay Echo (LDE)

6 meters has long been a passion, and it remains my favorite band. I know I can drop down to HF to initiate Global Communications on any of the DX bands, but 6 meters offers that surprise element which no other band can offer. When you get something on 6 meters (rare 😀), there’s nothing else like that feeling.

As a utility band, 6 meters has excellent ground wave propagation far exceeding 2 meters on the same power levels. Still, there is some misconception about its usability. This misconception is mostly driven by the DX mentality. From a DX perspective 6m is mostly useless, most of the time. As a utility band, it consistently offers good, stable, ground Wave Communications, whether it’s open or not.

While probing for openings on 6 meters, I actually heard my own signal come back to me, in my own radio. I sent out a CQ, then while in the receive sequence, my own CQ was displayed to me on the screen. I could easily accept a bug in the software as the cause of this however, I literally heard that incoming signal myself. If that weren’t enough, pskreporter also recorded the report of my own station receiving my own signal. So yeah, this was initially extremely confusing. In fact, I considered someone playing some kind of silly trick on me, but no one could have known I would have tested six meters on that day, at that time. Potentially what I heard was an echo of the signal I had just sent using FT8. Something I now believe was a long-delayed echo.

According to Wikipedia a long-delayed echo are:

“Long delayed echoes (LDEs) are radio echoes which return to the sender several seconds after a radio transmission has occurred. Delays of longer than 2.7 seconds are considered LDEs. LDEs have a number of proposed scientific origins.”

Read the Wikipedia article here

Back in my days of experimenting with yagi arrays for moon bounce on VHF, I understood the concept of a reflection or echo, resulting in signals bouncing off of the Moon, then being reflected back to us. Isn’t the delay from Earth, to the Moon, and back to Earth too short for what happened!? Honestly I’ve got nothing but questions.

So, if it was an echo of my own signal, what was it reflected off of? I suppose that question is actually the mystery.

Julian oh8stn

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1 Comment

  1. Julian,

    2.7 seconds is almost precisely the delay one would expect for a radio signal moon bounce. The moon averages 250,000 miles from earth, so 500,000 miles round trip. Radio travels at 186,000 miles oer second. 500,000/186,000 = 2.68 seconds.

    Love the blog btw.

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