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Hi all,

Maybe this is a very stupid question, but based on the topic about "Sensitive recievers" (http://www.domoticaforum.eu/topic.asp?TOPIC_ID=147) i was wondering if there is any chance on actually doing something usefull with this "noise"?

I mean, i have a weather station here with an outdoor temperature transmitter that transmits its data to the indoor station. Can i pick up this data and do something usefull with it? Or is it very unlikely that data from these "unknown devices" can be interpreted and used?

Regards,
Digit
who is a complete newbie on Rfxcom stuff...

Hello Digit,

There are different types of “noise”. I will try to explain how it works in this free course

The receiver always picks up RF noise. This type of noise is comparable with the noise you see on the TV screen when you tune to a channel where no transmitter is active. So when there is no X10 sensor transmitting the RF receiver will receive this random noise and the microcontroller just behind the RF receiver will sometimes be triggered to start decoding.

The other type of noise is not really noise. This is real data received by the RF receiver but the decoding software in the microcontroller can’t decode it. Most sensors will transmit with a different protocol and a different type of modulation and the frequency can vary.
A protocol is defined by the number of bits, the length of the bit patterns, start bit yes or no and type of coding (NEC, Manchester…).
The type of modulation can be FSK, ASK, OOK. The RFXCOM receivers use the modulation type OOK and they are programmed for a dedicated protocol.
The bandwidth of the receiver is small so that the signal of transmitters on a different frequency/channel is not received. Transmitters on a different frequency don’t create noise and they are not allowed to.

So it is possible that the X10 receiver can receive for example Oregon Scientific temperature sensors but this protocol can’t be decoded by this X10 receiver. With special Oregon Scientific decoding software in the receiver it becomes possible to receive the data. The next step is that the software on the PC must be able to decode the received data.

Mainly for this reason the RFXCOM receiver is modular and can have 2 type of receivers in an USB interface. For example: an X10 receiver and a Visonic receiver. Both protocols are different and are received on different frequencies. The RFXCOM Visonic code receiver decodes the Visonic protocol and translates this to X10 data. And so the PC software will only “see” X10 security sensors.

Regards, Bert