Putting an old digital clock (with an outdoor thermometer) on steroids
to: Building my own transmitter First step is to figure out what protocol does the outdoor temperature sensor speak to the clock. And pray it’s something simple. Given the clock is well past puberty now, it’s safe to assume it’s not going to be in the rocket science territory. Time to bring out the big guns RTL-SDR. Using the highly scientific approach of “let’s go through all the ISM bands while I pull the batteries in and out of the outdoor sensor,” I scored on 433.9 MHz: waterfall pic from CubicSDR and a bit of searching later, I landed squarely on
Source: wejn.org