Replicating a signal from a locating device (2.4ghz) to locate tag

Using Arduino Networking, Protocols, and Devices
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Hi, I'm new to this, not really much of an electronics/arduino buff so bear with me.

I want to create something which will do what my store-bought locating device (Loc8tor Plus) does, but I'd like to attach it to the roof of my house and make it operable from indoors.
Our 2 cats have homing tags on their collars that allows us to locate them and get them in at a certain time. It requires that I go outside looking all around the garden or if I'm lazy, from my windows, but often they're nowhere near the garden, and it sometimes requires several trips outdoors and lots of calling.
I don't want them staying out past 3-4 when the roads are busy, having lost 2 cats that way.
Also, by placing it on the roof of my house, I have a much better chance of detecting them, and if I can operate it remotely and simply toggle it to search for a tag constantly, while the loc8tor gives up after a few minutes if no signal is detected and requires manual input to retry.

So far, I've copied the setup from this thread: Poor Man's 2.4 GHz Scanner - Networking, Protocols, and Devices - Arduino Forum
I've tested it and it appears to work pretty well, it detects bluetooth signals and the signals from my loc8tor.

I need to mimic the signal my loc8tor puts out for each tag. They each have a unique signal so my loc8tor can tell which is which, so each tag would have to be registered (ie, have it's unique signal recorded) with my device.
Then, I need to know what the tag sends upon receiving the message. The tags aren't constantly working, they wait for a signal from the loc8tor, and then they send back a signal.

I can write a program to interface with the arduino remotely and to render the received data (via wifi probably)
It won't be as accurate as my loc8tor, but it it would at the very least indicate that the cats are in or near the garden which would be fantastic.

So, that's my plan... but the problem is I have next to no idea how to do this. I'm a
proficient coder, but my knowledge of electronics and RF technology is pretty limited.
Nevertheless, I'd really like to implement this as it would save me a lot of time and bother, not to mention chuffed to bits with myself for my burgeoning talent in electronic engineering!

Some help please?

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Hi,

I would like to start by apologizing for the necromancy, I am aware that this post is five years old. I found this post while looking for information for a very similar project, and figured my progress so far would be useful for other people who do the same.

I have similar tracker, the Girafus Pro-track-tor pet/cat tracker, and I believe the technology is close to identical.

The first thing you want to do is to open the device and look at the chip used. I tried looking at the public FCC data for your device, but the chip markings are smudged in the photos (this seems to be common practice). My device uses a CC2500 family chip from Texas Instruments, so I ordered some CC2500 modules from AliExpress.

The next thing you want to do is determine the frequency and modulation used in your device. I used a HackRF One to record some sample signals between the hand unit and tag. This gave me the precise frequency used. Then you need to look a bit at the signal to figure out other RF parameters, such as the modulation type used, BW, and data rate. It turned out my device uses MSK at 250 kbit. Universal Radio Hacker is useful software tool for this step, even though it does not explicitly support MSK.

For the CC-family chips you can get a CC debugger that lets you run the chips from a TI-provided piece of software called SmarRF Studio. This makes reverse engineering the signals much easier. The 250 kbit MSK turned out to be one of the suggested presets already set up in SmartRF studio, I only had to set the frequency and turn off CRC to get all the correct register settings for the CC2500 chip.

Now you can start to snoop on the communication between the hand unit and tag. In my case the protocol was very simple with some application id, tag id, command byte and probably link quality data sent back by the tag.

I then found some example code for arduino and the CC2500. I exported the chip register settings from SmartRF studio and modified the code, and was able to communicate with both hand unit and tag using a pro mini connected to the cc2500 module by SPI.

I hope this is of help to anyone starting on the same project!

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