trying to receive RF signals sent bij an outdoor weather station sensor

Yes - it's protocol 1, 342Hz, manchester coding - which I'd hope the code above will decode. Did you get a chance to try it?

The reason I think you'll get the 1s first is that there is a 'preamble' and sync pulse that is sent before* the payload (see the picture).

For the 'rolling code', the document says 'Value changes randomly every
time the sensor is reset'. I don't know if this means that the code increments by one after each transmission or not? Personally I'd just ignore it for now unless you find you're receiving data from someone else's weather station as well!

Personally I'd just try and get some data read in and then work backwards from there. Once you have the bits in the data variable, you can extract them with: parseInt(data.substr(nibble*4,4),2)

1 Attachment