�From:�	Bruce Metelerkamp (BRUCE)
�To:�		SOWACS@aqua.ccwr.ac.za
�Date:�	Tuesday, May 7, 1996  9:21 am
�Subject:�	TDR vs Radar vs shockwave reflection?

Frank Pitt writes:

Bruce, you write:
>(Concerning TDR and FDR.)
>Traditionally, most of these methods work at high frequencies,
but a contact of mine is developing a system that works at audio
frequencies!
>
>Any comments on whether it's possible, or whether it's been
done?

Er, I don't know if you've thought about this, but miners
searching for oil and geologists doing other things use what is
effectively an audio frequency TDR when they let off explosives
and listen to the shockwaves.

[Bruce Comments:] What came immediatly to mind was that TDR and
shockwave reflection are different principles: but thinking about
it, there is a similairty.

Is TDR just high frequency radar (the reflection of shockwaves?)
I think not. Explanations please those of you who are technically
minded.


While I'm on the line: anyone know where I can buy these
hand-held radar-based sensors that measure distance? (If they can
find steel in concrete and other models can measure distance,
then surely they could be adapted to measure the diameter of
objects?)

Thanks
Bruce Metelerkamp