half-baked

The wavelength of a 2 KHz sound wave and a 2 GHz radio wave are almost the same. If I set up a small speaker as a sound source and go running around the house with a sound level meter, can I get an idea of where the radio waves will go? This may not work well for absorbtion by walls, etc. (perhaps a conversion formula can be applied) but it might work ok for diffraction around corners and at the edges of objects in the signal path. A speaker wouldn't be an isotropic radiator but perhaps there's a way to make it approximate one.

Bruce

Reply to
bjs555
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Yes, that probably makes more sense. By the way, do you know of other applications similar to Netstumbler?

Thanks, Bruce

Reply to
bjs555

Here's a propagation calculator that takes diffraction from rounded surfaces and other parameters into account:

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It's the second program listed.

Reply to
bjs555

bseiler @ xspampatmedia.net without spaces and xspam

Reply to
bjs555

Isn't it just as easy to place an AP and run around with a laptop and netstumbler or similar? :)

Reply to
David Taylor

Well, let's see. Sound: 330 meters/sec / 2000 cycles/sec = 16.5cm wavelength RF: 3E8 meters/sec / 2.4E9 cycles/sec = 12.5cm wavelength Yep, close enough.

Interesting idea. The sound level meter may not be sensitive enough to operate at the same unobstructed distance that Wi-Fi will run at (100 meters) unless you really crank up the volume on the sound source.

It won't work at all through walls. Sound is propogated through walls by re-radiation of the sound. A wall moves slightly with the sound and causes the other side of the wall to move at the same rate. This re-radiates the sound. Wireless goes through some materials, but not others. Fiberglass insulation will block sound, but not wireless. Lots of other differences.

Another problem is reflection. Much of wireless propogation is by reflection. Different materials of reflecting surfaces simply don't reflect sound the same way they reflect RF. Interestingly, if they did, then the interference patterns would be similar for both sound and RF. For example, glass will reflect sound and pass RF.

It's not possible to simulate an isotropica radiator with RF either. Instead I suggest simulating a dipole using a conical reflector directly above a speaker pointed upward. The reflected sound will form roughly a donut shaped pattern.

Reply to
Jeff Liebermann

Kismet, Wellenreiter, Boingo client and if you want to go spend a whole load of money...Airmagnet.

David.

Reply to
David Taylor

ping me an email and i'll demo what airmagnet does.

Reply to
David Taylor

You're right. There are many differences. Also, sound waves aren't polarized like radio waves. Guess I'll have to call it a thought experiment only :)

Reply to
bjs555

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