direction finding

rjo_

I once got close getting a pilot's license. I really loved the experience. The most amazing fact that I learned was that if I got lost... all I had to do was follow my local AM radio station home.

Is this sort of thing ever used in robotics or is there too much reflection or too much hardware required to be useful?


Rich
ILMP

SRLM

At the hobbyist level, at least, I think the issue is distance. How far will your robot drive? Maybe a mile from your house? In a plane, you could be thousands of miles off course.

Carl Hayes

I'm currently designing and building an RDF unit that will do exactly that.· It's a Doppler direction finder that uses hard logic to switch four or six (can do either) antennas arranged in a circle, completing one circular cycle 800 times a second, and using a Propeller to measure the resultant change in phase of the received signal.· I can send you some articles on how Doppler RDF units work, if you like, but I wouldn't feel comfortable posting any of them in a public forum, which would not come under "fair use" of copyrighted material.

The principle is basically a simple one, although it can get a bit involved in implementation.· My RDF unit will weigh about a pound or so, not including the antennas, which are 19" whips mounted on a metal disk two feet in diameter.· I used a trash-can lid for the disk.

I'm working at 146 MHz.· For AM at 1 MHz, the antennas would have to be 100 times bigger for the same performance·-- so you should home on an FM station (between 88 and 108 MHz)·instead, or perhaps a NOAA weather station in the 162 MHz region.

SRLM, small planes don't get thousands of miles off course.· They don't have that kind of range.

Rjo, how do you intend to home on a station to get home?· Do you have a radio station in your house?· Having one a mile or more away won't do you the least good unless the people there will call you to come get your robot.

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· -- Carl, nn5i@arrl.net

Ugha

I think that the closest most of us can come to something like that is a beacon system... usually with IR.

If you did have a wireless link and connected it with a analog to digitial converter... you could have your robot move in random directions until it found one with the strongest signal... at least
that way you could make your robot find its way to your desk or something [noparse]:)[/noparse]