BT>   Don't let Blake Bowers know, but I've got some on-topic paranoia. On 
the 
BT> Evening News tonight, I saw what was described as a low-cost, short-range
BT> radar device. It was on a 2" square PCB, and the cost was said to be 
about 
BT> though this could drop to fifty cents. It can detect human heartbeats 
throu
BT> concrete. Great for finding folks buried in collapsed buildings.
Thought I'd engage in convo here.. Anyway, personally I've never heard of
any "radar" device that could do this.. I dont believe its really possible
(in such a small size).. at this point  in time..  Anyway, I believe they are 
referring to high-gain audio amps, the same as they've been selling for
60 years..   High-gain amps and mics have been used VERY EXTENSIVELY in
rescuing people from collapsed buildings, so it isnt any stretch of the 
imagination to think the device can be used for this purpose as its quite
common.   As for the claims that it  "detects heartbeats", I would simply 
say that is probably media innaccuracies at work. It does detect sounds,
but I really doubt the sounds are heartbeats.  The people who use high gain
audio for rescue applications, moreover just listen for general sounds,
people yelling for help, movement of debris, etc..  Not that it isnt possible
to detect sound almost as faint as a heartbeat, high-gain audio is an amazing 
thing.. Crank up the gain about 145dB, and use the most sensitive comntact
mics available and you can literally hear whispers through 8 inches of 
concrete if not much much thicker material than that.
--- GEcho 1.00
---------------