What modulation is this

[szangvil]

Hi All

I am new here. Just started to use RTL-SDR.

I managed to tune in to the desired frequency and record the audio of what interested me (433MHz Si1000 radio). I defined Si1000 module to use only 5 channels so I can easily see them in the waterfall, and after that, I selected one of the channels.

Can anyone verify that the waveform I am looking at in Audacity is in fact a GFSK modulated signal? The two channels I see are the I and Q parts of the signal? My goal is to try and demodulate it in Matlab, but I want to be sure that I know when I am looking at.

Thanks.

 

[br0adband]

Can't say that visual does anything to help me in particular but perhaps if you check out the Signal Identification Wiki at:

Signal Identification Wiki

you might track down something that looks similar. Because you've heard the signal yourself you can also check out the audio samples they have and potentially track it down that way. There's also the Digital Modes Samples page with more audio samples at:

Digital Modes Samples

Good luck.

 

[szangvil]

I found only what I mostly knew:

Quadcopter Telemetry Signal - Signal Identification Wiki

"This signal originates from the Silicon Instruments Si1000 Software Defined Radio (SDR) that is a component of the 3DR Telemetry Radio, sold for use as a data link between a computer ground station and a UAV "a drone".

It is typically sold configured for use on one of three ISM bands (433, 868, 915 Mhz) However as it is an SDR, a licenced radio amateur may set it to operate on other frequencies, and adjust the power level. You may see this signal in different forms on many bands, as the Si1000 SOC Radio is used for MANY MANY different applications. Shown in the image is only the default configuration for FHSS-TDM. This SDR can be programmed to send its telemetry (or other) data using BPSK, 8-PSK, and QAM at various constellation sizes.
Note that these values and uses are only in reference to the Si1000's minor use as a toy helicopter radio, the Si1000 and similar chips are not only highly adaptive but have the possibility of having custom, novel modulation schemes created by the end user(s). As such this chip and others of the same type or better now have uses such as Passive RADAR and Long Range Telemetry, Even Active RADAR in the hands of the general population. SDR SoC's have found military use for at least twice the time the public has been aware of them, as a consequence, mature integrated radio systems and technologies are flooding the market (one can purchase an SDR with a USB port and 2.8 Mhz bandwidth for 10USD)"

 

[szangvil]

Can anyone help me demodulate it?

 

[AggieCon]

Can you post the file, like in a public Dropbox folder? How did you record it?

 

[szangvil]

I used SDRSharp to capture the audio.

 

[szangvil]

Here is a another capture I did. Now I also plotted an IQ chart...