Raspberry Pi Forums

Hello,
i have two rf433 receiver. the first i bought on ebay has the "xy-mk-5v" reference. The second is an aurel RX-4M50RR30SF.
I have a DIO door sensor to test.
With the first receiver i can read the code send by the sensor.
On the second i get nothing except if i use a file to send a code.
I think it's because the first receiver has PSK/OOK modulation contrarly to the second which has AM modulation but i'm not sure it's because of this.
I measured the voltage on the data pin (number 7). I had nearly 1V when it received a signal.

What do you think about that?


thanks

Hi

Sorry if this is all obvious but your other posts suggest you are having problems.

OOK = on-off-keying. AM = Amplitude modulation.

AM is variation (modulation) of the size (amplitude) of the transmitted signal under control of the amplitude of a signal

In AM broadcast radio the size of the control signal (the music) is limited so the r.f. level increases and decreases but never exceeds the instantaneous power rating (or license limit) of the transmitter and the transmitter never turns off - there is always some power transmitted. The music is an analogue signal, the rf power is always proportional to the signal level. Modulation is typically 30% or less. During silence the transmitter power is at some middle value.

OOK is the same except the input signal is not limited; it is so large that the modulation is 100% - transmit power is either 100%, or zero. It alternates between these two values during signal transmission and remains off between signals.

Both the modules you mention are designed for OOK. Where did you get PSK from?

Both modules are available for operation at 433MHz.

The xy-mk-5v is very cheap and nasty but (despite what people say elsewhere) is quite capable of 10m range within my house - I have several working here as I write. The tuning of this thing is quite broad and generally receives anything in the band.

The RX-4M50RR30SF is a much more sophisticated beast. It actually has a specified bandwidth. Generally one would expect it to perform better - provided the r.f signal is actually on band. I assume you are in Europe, and the door sensor is 433M not US 315M. I think the xy-mk-5v might well receive 315m signals but with very, very low sensitivity.

Without test equipment life can be hard. Both these modules produce random noise when no r.f. signal is being received. If you connect a LED to the output - using a single transistor buffer - you can see the random flickering change to a definite pattern whilst ever there is a 433M signal received - any signal including my various car keys. You can buy filter modules to remove this noise.