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Gary wrote:
 George, that was a scintillating observation.

On May 7, 1:50 pm, "George Huxtable" 
wrote:

> The radar reflection from a boat, illuminated by a coherent signal (which
> radar is), is the sum of all the reflections, that return toward the radar
> scanner, from all the different bits of the boat, summed up togeter. And
> when you sum them, you have to take account of the phase shift in each case,
> from each bit of boat, because the double-distance, from scanner to
> reflecting surface back to scanner, is different for each bit. The detected
> returned power, the integral of them all, will depend critically on the
> boat's geometry and the angle of the boat's attitude to the beam. There's
> nothing to prevent that returned signal summing up to zero, or near-zero, at
> a particular attitude, simply because that jumble of returned signals
> happens to cancel out to zero, a null-reflection, because of those differing
> phase shifts. Luckily, a small yaw in the boat, or changing direction from
> the radar antenna, will make it visible again. That's one reason for the
> complexity of radar image behaviour; the way they tend to "twinkle".
>
>


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