Re: Listening to TC?

["Tesla list" <tesla@xxxxxxxxxx>]

Original poster: William Beaty <billb@xxxxxxxxxx>

On Sun, 4 Sep 2005, Tesla list wrote:

> Original poster: Jerry Chamkis <jchamkis@xxxxxxx>
> the one you really want.  They behave just like an ordinary capacitive
> transducer, the polarizing voltage is typically 200 v.  You can find a
> (very!) wide spectrum of B&K instruments quite cheap but the capsules hold
> their value depressingly well.  It wouldn't be hard at all to build a
> heterodyne listening-box.  I think such things (although presumably NOT with
> B&K capsules :-) are still used for detecting insects.

The cheap and crude version:

http://pw1.netcom.com/~t-rex/BatDetector.html

http://home.kabelfoon.nl/~bertrik/bat/

http://www.goldmine-elec-products.com/prodinfo.asp?number=C6897

http://www.goldmine-elec-products.com/prodinfo.asp?number=C6899

http://www.goldmine-elec-products.com/prodinfo.asp?number=G951&variation=&aitem=9&mitem=9


>  > sounds, but what about "ultrasounds"? These would be sounds from 15KHz on
>  > up to the resonant frequency of the coil. This question is 
prompted by the
>  > following: Last night, a bat got into the instrument/people 
section of the
>  > lab. (The TC section is inside a grounded 10ftx10ftx8ft cage). With the
>  > coil running, the bat ran into the wall the way a bird or 
insect will beat
>  > against a window trying to get out. I turned off the coil and it
>  > immediately turned around and flew back out the door which was only open
>  > about 5 inches.  Makes me think maybe the coil was making sonar-jamming
>  > noises. Of course, it could be pure coincidence.

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William J. Beaty                            SCIENCE HOBBYIST website
billb at amasci com                         http://amasci.com
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