Wireless Parabolic Mike + SDR Dongle

spongella

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May 12, 2012
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Central NJ
Made this parabolic microphone that is wirelessly linked to an RTL SDR dongle receiver.

The audio circuit is a kit from Radio Shack consisting of two tiny microphones and an audio amplifier, runs on 3 AAA batteries. Audio is fed into a Scoche FM wireless xmitter tuned to 107.7 MHz seen hanging on top edge of the baffle.

Inside the house is a dongle-SDR tuned to 107.7 MHz using HDSDR for listening to the sounds of early morning songbirds via the parabolic microphone. Using HDSDR's audio analyzer on lower pane, you can see the audio fingerprint of the birds as those long bands from 3000 - 5500 Hz. Gives you an idea of what audio frequencies are of things such as crickets, birds, traffic, gunshots, etc.

You can also record these sounds using HDSDR; I do have a .wav file of the songbirds, but cannot upload .wav file. They come in crystal clear with this setup.

This is a fun way of listening to sounds and looking at their audio "fingerprint." Not very high tech, but something the average guy can build.

Started out using just a Ku band dish as a reflector, but it was too broad and not very directional. This was published in MAKE magazine in the spring, in the spirit of full disclosure. Thought some of you folks might be interested since we do use parabolic dishes as reflectors. Just a tangential application of FTA.
 

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spongella

Thread Starter
SatelliteGuys Pro
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May 12, 2012
1,300
884
Central NJ
Voice imprint of house finches - parabolic mic was aimed at the bird house about 70 feet away. Notice the similarity of the two imprints in the 2300 - 6000 Hz range.
 

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