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Mar 22, 2009, 06:49 PM
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Maxbotix rides again.

The answer is yes. A USB PIC sampling at 157khz can record a Maxbotix. The factory frequency came in around 38khz.

55khz turned out hopeless. The champion was 40khz. The PIC starts falling over above 40khz, so 55khz time constants really produce 40khz.

The Maxbotixes worked best with shrouds removed, a delay loop of 2 samples, inversion, & fuzzy logic. Higher sample rates R better. All the noise comes from the microphone. Software made it much more omnidirectional but nothing has matched audible sonar with the $200 PC soundcard.

Correlation didn't work with the Maxbotix. One idea is its bandwidth is too narrow, so U get noise of the same frequency correlating with the pings. Another idea is the PIC time constants not working.

AGC for op-amps is dead. The best AGC is the maximum receiver gain while adjusting the transmitter power.
Last edited by Jack Crossfire; Mar 22, 2009 at 08:48 PM.
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