Tracking a radio signal

[DonRotolo]

Originally Posted by Mike

Unfortunately a google of "doppler radio direction robotics"

Drop the "robotics"

The Ramsey kit is the size of a textbook (plus antennas), you need a radio receiver for the frequency of interest (you pick the size) and a power source (ditto). I could fit it all into a Cheerios box (but the antennas would poke out) with room for breakfast.

3 or 10 over a square mile as PoC is doable, but scalability will frustrate you even at the hundreds level. The only way around that is a fixed (land-based) antenna network, which doesn't sound practical here. (A friend's company does exactly this, providing equipment location within a hospital. Handy if you need that <equipment name> NOW to save a life)

Research Spread Spectrum, Alan's comment is absolutely valid and when you get past the PoC stage allows for scalability.

(Here's a thought experiment for you: Imagine instead that each device chirped an audio tone, and your 'antenna' was a microphone. How many chirpers before you can't tell one from another? Repeat with chirpers on any of 500 random frequencies (=spread spectrum). Now how many?)

By the way, the Ramsey kit is just an "antenna", you can easily connect up a spread spectrum receiver to it as well.

[Mike]

Originally Posted by Don Rotolo

Drop the "robotics"

The Ramsey kit is the size of a textbook (plus antennas), you need a radio receiver for the frequency of interest (you pick the size) and a power source (ditto). I could fit it all into a Cheerios box (but the antennas would poke out) with room for breakfast.

3 or 10 over a square mile as PoC is doable, but scalability will frustrate you even at the hundreds level. The only way around that is a fixed (land-based) antenna network, which doesn't sound practical here. (A friend's company does exactly this, providing equipment location within a hospital. Handy if you need that <equipment name> NOW to save a life)

Research Spread Spectrum, Alan's comment is absolutely valid and when you get past the PoC stage allows for scalability.

(Here's a thought experiment for you: Imagine instead that each device chirped an audio tone, and your 'antenna' was a microphone. How many chirpers before you can't tell one from another? Repeat with chirpers on any of 500 random frequencies (=spread spectrum). Now how many?)

By the way, the Ramsey kit is just an "antenna", you can easily connect up a spread spectrum receiver to it as well.

Proof of concept is all I need for now.

So using this DDF kit I will be able to point, within 22 degrees, towards the beacon with the strongest signal strength? How would I go about decoding the signal then, another directional antenna pointed in the approximate heading? What happens if there happens to be two or three beacons there? I feel like the DDF guiding the directional antenna doesn't provide enough resolution in case there are two beacons in that heading. Can I use the DDF kit to both find the direction of the radio and decode anything incoming?

Thanks
Mike

[DonRotolo]

To receive the signal, use an omnidirectional "ground plane" antenna. Very inexpensive and small.

The DDF signal varies too much to decode data from it, generally speaking. There are ways around it, but not easy ways.

Yes, you may in fact receive signals from more than one transmitter, but your flying algorithm will not simply pick up 'one' signal and fly at it, instead you'll fly past it and note where it was, then turn and fly at it. Or, said another way, you need to find the right one before you can steer towards it.

Try this on a regular map. At one spot, you get the target at a bearing of 110 degrees. At another spot, you get the target at a bearing of 150 degrees. You turn 90 degrees and get the target at a bearing of 120 degrees (all measured relative to the aircraft) again. Draw lines to infinity from those locations, where they cross is the target. Now go there.

Again, this isn't a trivial problem to solve, but I still think it is within your budget and reach. Before committing to air, I'd first learn how to find the transmitter on the ground. By breaking this problem into manageable pieces, what you learn on foot will be easier to use int the air.