[sdiy] reverb - the catch?

[Paul Perry]

Back in the 60s, a short range air radar tower
I woeked in used a mercury delay line.
The idea was to record the decoded echoes from
one sweep, and subtract from the next sweep.
That way, you could remove much of the
clutter & moving objects (planes) showed up
clearer.
I don't know how the signal was modulated before going
into the delay line, but personally I'd go for FM.

interestingly, a modulated reflected ultrasonic
beam has been proposed as an echo device. If audio
modulated & fed around a room, I guess you could get a
reverb effect, that could be modified by walking around!

paul perry Melbourne Australia

----- Original Message ----- 
From: "Mike"

> Just a thought. I did some work on sonar processng geat a long time ago,
and
> I vaguely remember somthing about accoustic delay lines from then. they
used
> mercury tube delay lines as memory in early computers.