Where to start, need to listen to 800-900Mhz range

[webtop]

I am trying to reverse engineer a device that uses an RF protocol, that transmits and receives in the 800-800Mhz range.

How would I go about building something to help me capture the packets being sent to/from this device, without tearing the device itself apart?

If this isn't possible, I can always buy a second copy of the device and solder some wires into the circuit to see what is going on, but before I do that I want to know if there is a circuit I can build to "listen" to this device.

Thanks for any and all help. Very much appreciated.
Paul

[metrologist]

I would be looking at the cheap SDR units being discussed here, and some software plug-ins to capture the I/Q data streams and work from there...

[bjcuizon]

Yes, cheap $10 dongles will work fine if you want to get a basic signal out of it. And then probably use some kind of virtual audio cable to connect the output of sdrsharp (the sdr software) to the decoding app.

[hamster_nz]

If you can wait till Christmas one of these could be helpful....

https://www.crowdsupply.com/lime-micro/limesdr-mini

(But you only get a 30MHz band at a time, which might not be  you are after....

[scatha]

I'd definitely lift the lid and see if there is an easy way to access the baseband data (transceiver SPI ports, etc). If so it will be much, much quicker to do this rather than capturing the IQ data, establishing the modulation/coding scheme, then demodulating.

[Richard Crowley]

I just watched a really excellent YouTube video: Michael Ossmann: Simple RF Circuit Design
Mr. Ossmann designed very popular products like HackRF One, Ubertooth One and YARD Stick One, etc.
One of the most valuable parts of the presentation was his recommendation to use SDR as a great budget-price form of test gear.  Highly recommended.

https://youtu.be/TnRn3Kn_aXg?t=57m30s