Sniffing pH Sensor RF Signals for Feedback Re: Your Esophagus

For about a week [Justin] had a wireless acidity level sensor in his esophagus and a pager-looking RF receiver in his pocket. So he naturally decided to use an RTL-SDR dongle to sniff the signals coming out of him. As most of our Hackaday readers know, these cheap RTL2382U-based DVB-T receivers are very handy when it comes to listening to anything between 50MHz and 1800MHz. [Justin] actually did a great job at listing all the things these receivers can be used for (aircraft traffic monitoring, weather images download, electric meter reading, pacemaker monitoring…).

After some Googling he managed to find his Bravo pH sensor user’s guide and therefore discovered its main frequency and modulation scheme (433.92MHz / ASK). [Justin] then used gqrx and Audacity to manually decode the packets before writing a browser-based tool which uses an audio file. Finally, a few additional hours of thinking allowed him to extract his dear esophagus’ pH value.

Comments

  1. mixadj says:

    Slightly off topic. I have never heard of these sensors. How are they placed? Do they use surgical(incision) methods or some kind of wicked strong superglue?

  2. Joshua T says:

    Is that a typo: is it supposed to be “RTL2832U-based” instead of “RTL2382U-based”? Just wondering.

  3. Andy D says:

    Amazing hack and written in a understable way! Thank you Mathieu! I might use this to try and catch an MSP430 RF signal :-)

  4. yatko says:

    interessting. for me specially the part how you decode via FF :) but does not work in FF >28. anyone have any idea how to decode with C or in a different way?
    Also, I have a FM modulated binary wav. how to deal with that?

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