In article ,
"Bruce Woodburn" wrote:

I saw an interesting artifact while in the North Atlantic. With the range
set to 30 miles, we had a huge reflection at 25 miles... would have been
several miles long.
We were several hundred miles offshore, perfect visibility and there was
definately nothing there.

The puzzle was solved when we realised the artifact was on the same bearing
as Bermuda, 350 miles away. The antennae was catching Bermuda's reflection
of the previous pulse (which was interpreted as reflection of the current
pulse from an object 25 miles away). The difference in distance (times 2)
divided by the speed of light equaled the pulse frequency of the radar unit.
Isn't physics great when it works?

The artifact lasted about 20 minutes. We were in the area for another month
but never saw the effect again. I assume it had something to do with
atmospherics skipping the signal.

Anyone ever seen this?

Bruce



We see that type of reflection here in alaska all the time.
One of our usual weather conditions in the summer is "temp
inversion" where we get considerable RF reflection at the inversion
boundry. I have watched a similar Radar Target appear and
hold steady for hours at a time on an Xband Radar in Bristol
Bay, Alaska. It is a Radio tower 90 miles from the Radar Site
and well below the horizon. This same phenomena is used widely
in the area to communicate on VHF Radio Links out to 200 miles.
One of the "Old Radiomen" (Bill Forgey) pioneered (in the Late 60's)
4 or 5 of these "Shots" for the Canneries to communicate between
themselves on VHF. Most of these links are still in use today.

Bruce in alaska
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