Tracking a radio signal

[DonRotolo]

Originally Posted by Jared341

Simply rotate the antenna

A valid approach, but you then have the issue of coupling the RF signal path through a rotating joint, not trivial.

Originally Posted by Jeff Pahl

Do multiple beacons transmit at the same time? That will be a problem, as due to the capture effect you will only hear the loudest beacon, which may not be the one you want. If they transmit one at a time, then you can listen for the id of the beacon you want.

The same thought occurred to me last night. Unless they have some kind of synchronization, you're going to get data collisions all over the place (look up Hidden Transmitter Syndrome) and in a practical application you won't hear any of the transmitters well enough to decode their data.

I asusme they are simply low powered transmitters, not equipped with enough intelligence to synchronize, and without a receiver for a DAMA-type synch protocol.

If they were laid out in a known pattern, you can use whatever you receive to know 'where you are' so you can get to 'where you need to be'. But if they are scattered randomly _or_ mobile you have to just search until you hear what you are looking for and zero in on it before you lose the signal.

Also consider how often each one pings. If the ping is 5 bytes (TX_ID is 2 bytes) you have 40 bits, at 1200 baud that's (40/1200 = 1/15) of a second per ping, add a small randomization in there (two TXs that collide every time is a problem) you can see maybe 10 pings per second, with 200 TXs you might be able to ping once every 20 seconds (at best), which is far too slow even if you fly at 30 MPH (44 fps) since you'll move (44*20=880 ft) between pings.

I want to emphasize that this entire "problem" is absolutely solvable (with college-student-level resources) but not trivial. There is plenty of info published on these topics. Again, ask whatever questions you have.