Interesting part

From: William Donzelli <aw288_at_osfn.org>
Date: Mon Jun 14 15:08:59 2004

> They originated in WWII radar, where they were used to remember the last
> received signal pass, so they could detect differences with the current
> signal pass, and cancel out stuff that didn't change.

Just post war, actually, at least in Allied radars. The Germans had some
sort of MTI technology in World War 2, but I don't know what they used.

The only World War 2 radar set that used a liquid delay line is the
AN/APQ-15, a spoofer. It used an odd oil I have never heard of before,
filled into a tank. A received pulse was amplified and sent to a
transducer in the tank. The (now) acoustic pulse would bounce around in a
semi-random pattern, and another transducer would pic up these echoes,
then retransmitted back to the offending radar. The idea was that one
AN/APQ-15 could "look" like a whole squadron of bombers, simulated in a
tank of oil.

William Donzelli
aw288_at_osfn.org
Received on Mon Jun 14 2004 - 15:08:59 BST