In SX Microcontrollers, SX/B Compiler and SX-Key Tool, black68cougar wrote:

Build it. No, I'm not kidding. It's not that hard.   

The hard part is the directional antenna array, and a little research on the web will tell you every thing you need. 

If you have two directional antennas at 90 degrees to each other and the RF source is within that arc, and with range, the difference in signal strength will tell you where within the arc the source is. So if you have 4 antennas, you can now cover a full 360 degrees.

Now you either have a receiver per antenna, or you multiplex the receiver to each antenna, measuring the signal strength at each antenna.

Another way is to use a single directional antenna and mechanically sweep it through 360 degrees looking for the angle of the strongest signal.
I'm sure you have seen the RADAR antennas sweeping around and around or back and forth. Or the spy with a little box going beep-beep-beep 
swinging the little box back and forth.


Now to get the distance - get th baerring from two points and triangulate.
Or you can cheat a little if you know something about the source - like its amplitude.

If you know the amplitude at the source and the amplitude at the receiver, the distance between them is directly related 
to the difference in amplitudes. (if you build the source transmitter, have it actually send the signal strength - then you can compensate for "week batteries".)


An other way this is done is to have two HIGHLY accurate syncronized clocks, one in the transmitter and  one in the receiver. The transmitter just sends the time. The receiver uses the difference between it's clock and the received transmitter clock to calculate the distance - (this is sort of how GPS works)


OK, its not that easy(you would not have read this if the first thing I sayed was it was hard ... LOL) - but it would be a lot of fun to do it - and the pride of accomplishment - and the things you would learn along the way ...

The concepts are simple:
    There is a constant autenuation rate  - the signal lose is directly related to the distance.
    There is a constant propogation rate - the time it takes is directly related to the distance.
    Signals appear to travel in straight lines (unless they  bounce).

Now you get the fun of doing the engineering.


If you want more info, just ask, I'll see if I can help

Doug

---------- End of Message ----------


You can view the post on-line at:
http://forums.parallax.com/forums/default.aspx?f=7&p=1&m=230474#m230959

Need assistance? Send an email to the Forum Administrator at forumadmin@parallax.com

The Parallax Forums are powered by dotNetBB Forums, copyright 2002-2007 (http://www.dotNetBB.com)