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01- 2007, # 009
Some things we did know. It was
not ham operators. It was not a hoax. It was not foreign
intelligence. It was not one of our own transmitters.
It was not a recording. (thank
about that one, and why you know it was not an audio recording!)
It was not one of our field stations. It did not fade.
It had no Doppler. It was our keying, at our speed.
It was reasonably strong, but not enough to trigger AGC on the
receiver. It was very clear, with no QRM. It was in
the 6 MHZ band.
I have never heard another one.
I have some theories about LDEs, but I'm no scientist, so I just
keep them to myself, mostly. I think the key, though, is
the word 'ducting.'
An LDE happened to me once, back around
1963, at a near sunspot minimum. About 3AM Eastern Time,
I don't remember what season, I was trying
to hear ANYTHING on 40 meter CW. The band was dead, and
the noise level was very low. I had called several CQ's,
and heard the last several letters of my call coming back about
3 to 4 seconds after I sent them. I tried a few "dits",
and they came back just as I sent them. This went on for
about 5 minutes. The returning echoes sounded like they
had come a long way, all fluttery, and just above the noise level,
but on the same exact frequency, and matching my fist exactly.
I'll never forget what they sounded like.
I just wanted to add my experiences with LDE's. In
the late 60's I spent quite a bit of time on aircraft carriers
in the Mediterainean and we were running lots of phone patches.
On numerous occasions I heard the last several words we had transmitted
after we unkeyed the transmitter. At
first I thought it was someone playing a prank but I soon realized
it was our signals. The delays were longer during times when the
propagation was best and as I remember I never heard them during
daylight hours which figures in with the ionaspheric conditions. I agree it is an odd sensation
the first few time you hear it.
experienced LDE on 11M (CB SSB) back in the late 80's. A
friend would be in town and drive to college some 50 miles away.
He'd go mobile and I'd use my base station. The almost
half way point, 27 miles, was where we would have to sign off.
Sometimes we'd make it a little bit longer, but rarely
too much farther.
One evening as he is headed back to school as he got further
apart, we kept hearing another station jump in. He'd hear
one when I talked, I'd here one when he talked. But they
would not reply when we addressed them. As he got further
away we noted that we were hearing a delay of the original transmission!
Once past the half way point we could hear each other
from the delayed transmission. This was one of the only
times we could hear each other the full 60 or so miles. Eventually the echo faded
and we lost contact.