Hello!
I was wondering if it is possible to make a "finder" with arduino. It would be something like the devices you see in movies that beeps faster as you get closer to your target, and might have a direction pointer.
Don't know what this would be called, so I'm having a hard tme finding any info on the interwebs.
Anybody have any ideas?
I think you may need to ask the movie SFX department! 
So you need avalanche beacon,
Transmitter and receiver with 2 orthogonal ferrite antennas
Thanks, but the avalanche beacon is just too expensive for this project 
Perhaps there is a reason why 'the avalanche beacon' is expensive, is it possible its not so simple\cheap to implement ?
But your description of your project or requirements are so vague its unlikley you will get meaningful advice.
How should the "finder" know what it is to find?
Let's see if ai can claclarify a bit.
I want to place an object somewhere on a field. I would then like to find it by using a tracking-beacon sort of device. As I walk around the field searching for the object in question, my hand-held tracking device is listening for the beacon. If I come within a preset distance from the object, my tracker starts to beep, alerting me that the object is within range. Now, as I move closer to the object, the tracker would beep faster as I get closer, if I move in any direction away from the object, the beeping slows down.
I was thinking of maybe an rf transmitter and receiver, 433mhz kind as the basis of the idea, but don't know if it would work.
Plenty of ways of locating a 'transmitter', its a sport in the Amateur Radio fraternity, do a Google search on 'Fox Hunts'.
But you wont be able to measure distances unless you use a transmitter thats sends GPS co-ordinates or is a RF device capable of measuring the time of flight of transmissions such as the SX1280 LoRa devices.
To expensive to buy, very cheap to do it ( basic) 1 MHz transmitter and 1MHz receiver - regular AM receiver. Then you make improvements to achieve as you describe in first post.
2 receiver antennas + am detetctor + phase detector.
https://makerf.com/posts/more-fun-with-crystal-oscillators-amplifying-rf
Post # 6
Modulated rf signal.....
Never used LoRa devices before, or any gps device for that matter. I don't need the precise distance, I was thinking of a way to pick up on the intensity of the beacon as you approached it. Is that the same as you are referring to?
I might look further into this solution. Thanks.
Picking up the 'intensity' of a transmitter is easy enough, but it wont tell you the distance.
For a given intensity the distance could be 10M, it could be 200M, depending on the exact location, orientation of antennas, nearby objects, environment etc.
Blasted! This little project is turning out to be not as simple as I imagined.
The LoRa SX1280 devices will do the job. The receiver can give you the RSSI which you could use to drive a buzzer frequency or Neopixel LED in combination with a simple body fade technique to give you a direction and the ranging feature will give you the distance, read about it here;
https://stuartsprojects.github.io/2019/04/26/Semtech-SX1280-2-4Ghz-LoRa-ranging-tranceivers.html
The ranging feature works best in open fields too .......
Current LOS record for the SX1280 ranging is I believe 85km;
Thus my reply in #2. 
Amazon has SX1280 modules for under $20. They even have a connector for an external 2.4 GHz antenna.
You could use RSSI (Signal Strength) and a directional antenna to get rough direction and use the Time-of-flight measurement for distance. Turn to get the maximum pitch and then move closer to get more rapid pings. Sort of like in the movies!
Or maybe two directional antennas and an antenna switcher to get an arrow pointing roughly based on relative signal strength.
And guess what, directional antennas for 2.4Ghz are both small and dead cheap, due to thier being popular for WiFi.
And apparently, although its not mentioned in the SX1280 datasheet, one of the devices registers reports the RSSI of the ranging exchange, so you could do RSSI and distance measure at the same time, thus avoiding flipping packet modes all the time.
This is interesting. RSSI and using TOF seems might due the trick.
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