So I have a meteo station using 433MHz to communicate with the base. I was wondering if I would be able to use a 433MHz reciever to get the °C and humidity % of the sonsor ? A code like this could already exist ?
It is possible but unlikely.
There are many weather stations on the market that use 433MHz signal. But knowing the frequency used is not enough. You also need to know the data encoding method used and the message format shared between the base station and the remote sensor. These will all be different between manufacturers and models. So you would need to know which make & model you have, then Google for any projects that have successfully reverse-engineered the signals from that exact model.
Here is an example where someone has reverse-engineered the data signal from an off-the-shelf outdoor temp sensor. This should give you a sense of how difficult this process can be, even for an electronics expert.
It may be easier to build your own sensors, then you can decide how the data is encoded and transmitted.
Maybe You check what standard, what protokoll the wheater station uses and then poke around and find out more about it. It can't be a secret.
Railroader:
It can't be a secret.
Yes it can, at least in countries where the law protects intellectual property.
That was useful for me as well. Thank you!
What about sending discrete, digital and limited range signals, to be assigned to specific significance at the receiver end?
For instance:
1= low temperature <10 Celsius deg
2= average temperature 10<t<Celsius 20 deg
3= above average >20 Celsius deg
+++
In my mind, it really depends on what the sensors measure.
a) If the sensors measure a sort of enclosure, which has highly different temperature than at the receiver place, then it makes sense to send accurate temperature. Of course, depends of the required accuracy.
b) If the sensors measure the same environment - or close to - as the receiver place, then perhaps detecting the differences makes sense.
A meteo station that send radio signals from 1 km distance to the receiver may be relevant in specific cases, such us mountain area or balloon mounted.
Or, in other words, how far can be the transmitter to the receiver to be still reliable, considering real word: forests, houses etc.?
PaulRB:
Yes it can, at least in countries where the law protects intellectual property.
Keeping things secret and laws protecting intellectual property are two very different and by and large unrelated things. After all, the purpose of patents is that to protect an invention it must be fully opened up.
Now indeed many such protocols are sadly kept secret - and without OP disclosing which exact meteo station they're working with there's not much that can be said about possibility to communicate with it.