spy microphone

[sss]

hello everybody

my friend showed me a special mic that u can point on somebody and hear him from 100m away !
does anybody know how to make one of those mics ?

[audioPT]

Search the web for diy parabolic mic

or try to do something like this:

[sss]

do i have to use some kind of special matterial for the dish?

[Sch3mat1c]

No.

But you get better response from a shotgun mic. Take a whole bunch of lengths of tube (copper, brass, electrical conduit, plastic, cardboard, as long as it's solid it don't matter) and cut them to graduated lengths. So you could have like...30 pipes from 5 to 20 inches length. At the near end you fit a dish with a mic in it. Idea being each pipe picks up a narrow range of frequencies, so you get good response from a lot of them. And being straight, it's very directional.

Kinda big though, and doesn't have the movie appeal that makes parabolic dishes so popular.

Tim

[Swedish Chef]

For a real "spy" mic you could try a reflected-laser-beam kind of mic. With these you can mic up conversations in rooms with windows up to a distance of 500 m or more. Only suitable for glass windows though, not conversations in free air.

/Magnus

[sss]

wow sounds cool
is it diyable? pics,schematics....?

[Sch3mat1c]

No, not really. I hear they work like crap, and like he said, only on glass. When you're exactly perpendicular to it. Etc.

FWIW, the idea is LIDAR - you could do it with a microwave and a metal building (i.e., RADAR) if you made a 2.45GHz phase demodulator.

Tim

[sss]

i'll stick to the dish
gotta find one though

[chemelec]

Check out the Parabolic Mike Project on my website.

My Projects

[thespeakerguy]

Sorry, late post, but this is for future researches.

As a kid we played with a mic element in a rubber traffic cone. This worked very well. It was before we understood parabolas. Most of my stoner friends probably never will understand parabolas.

Anyway, what I'm trying to say is play with it, the shape is not too critical, athough a parabola is best. You could make a segmented parabola out of corrugated cardboard.