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Jul 03, 2007, 01:06 AM
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RF terrorism

So gave up on the handheld serial console for a while. Maxim actually has a free replacement part for the Palm, but it won't arrive for some time. Meanwhile, it's back to the laptop.

The biggest problem with 2 way communication is now 75Mhz RF interference with the output of the 2.4Ghz receiver. The output appears DC biased. Tried many strategies to defeat it.

Our favorite was a low voltage differential output from 2 op amps and that only worked marginally with the 75Mhz antenna retracted. It didn't work at all with the antenna extended.

Suspect it isn't DC bias but 75Mhz oscillation, but can't see it without an oscilloscope. Really need shielded cables and shielded circuits for everything. Another possibility is using MAX233's to send RS232 levels. Maybe analog low pass filtering, but we don't do analog low pass filtering in this dumpy apartment.

Also, with the 75Mhz transmitter powering custom transmitter modulation and the 2.4Ghz receiver, it dies within minutes. Just not enough power in the NiCads.

Should work on inertial sensing again. Thinking about just doing AHRS in the Kalman and position using pure GPS.
Last edited by Jack Crossfire; Jul 03, 2007 at 01:15 AM.
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