How to interpret this signal?

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royb
Posts: 4
Joined: Fri Feb 21, 2020 12:24 pm

How to interpret this signal?

Post by royb » Fri Feb 21, 2020 12:51 pm

Hello,
I am new to the signal hacking, and after reverse engineering my wireless doorbell succesfully at 868MhZ, now I want to try and decode the communication between my Gas fireplace (or more specifically its Mertik Maxitrol gas valve unit) and its remote.
The communication is 2 way, as the LCD screen on the remote sometimes gives feedback like error codes and such.

The signal I am receiving looks distorted or quantized, and I am wondering wether my radio is to cheap to correctly interpret this signal, or wether I need to go at this in a different way.

Here is the analog view of the signal, it looks like theres 2 sinus waves interjoined. Why do I see my signal like this? Is this some kind of scrambling / encoding? A more advanced sort of modulation?
signal.png
signal.png (86.43 KiB) Viewed 2000 times
Also when I do spectrum analysis (see below), I am seeing a signal over about 100KhZ of bandwith containing multiple (7) peaks. Could this all be part of a 7 level FSK modulation? What else could these peaks represent?
spectrum.png
spectrum.png (113.55 KiB) Viewed 2000 times

hotpaw2
Posts: 128
Joined: Sat Jan 14, 2017 11:07 pm
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Re: How to interpret this signal?

Post by hotpaw2 » Fri Feb 21, 2020 3:46 pm

One possibility for multiple evenly spaced carriers would be some form of OFDM.

royb
Posts: 4
Joined: Fri Feb 21, 2020 12:24 pm

Re: How to interpret this signal?

Post by royb » Fri Feb 21, 2020 11:27 pm

hotpaw2 wrote:
Fri Feb 21, 2020 3:46 pm
One possibility for multiple evenly spaced carriers would be some form of OFDM.
Im going to give it a try in GNU Radio to demod this signal as OFDM. Thanks for the hint.

Username
Posts: 570
Joined: Sun Oct 09, 2016 7:27 am

Re: How to interpret this signal?

Post by Username » Wed Apr 08, 2020 1:25 pm

Maybe is the signal so strong it overload the SDR and how multiple signals?

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