as in the tile, I've tried to sniff a 433mhz radio signal with my raspberry pi 3b but something failed the receiver is one of the cheaps available in the web, 5v powered.

I've followed this tutorial https://www.princetronics.com/how-to-read-433-mhz-codes-w-raspberry-pi-433-mhz-receiver/, and used the command in the link (sudo RFSniffer) then expected for some codes in the terminal, but no code appeared, so I suppose the command works but something was not correct here the wiring: VCC - 5V (tried also with 3.3 but nothing happened) DATA - GPIO 27 (pin 13) GND - gnd

In my idea, or it's a receiving problem or a printing problem in the terminal

The receiver was directly connected to the breadboard (I have no female jumpers) but it was a good connection, the sender was 1 garage remote and 1 tv remote, both very close to the receiver.

Have noticed on the back of the receiver there are 3 marks: 433mhz - 415mhz - 355mhz, maybe a setting receiver problem?

Does it's possible the signal was encoded in some way that the RFSniffer is unable to read and print?

I supposed was an easy project, but it seems now complicated. can someone help me please?

Thnx in advance

  • 1
    You've apparently not read the documentation before posting your question; please take the "Tour", and read "How To Ask A Good Question". I will point out this: The tutorial you've linked in your question is for an Arduino - not a Raspberry Pi. Have you asked the author of the tutorial for help? If not, please do so. We're glad to help with specific questions, but we can't proofread every tutorial on the Internet - esp those for Arduino!
    – Seamus
    Jan 22, 2019 at 14:44
  • oops, im sorry! I edited the link
    – onec0de
    Jan 22, 2019 at 17:09
  • 1
    See if piscope can see the signal. abyz.me.uk/rpi/pigpio/piscope.html
    – joan
    Jan 22, 2019 at 22:06
  • hello I've tried to run Piscope but I had a strange result: in fact when launched the Piscope & command the pgpio 27 was already in use, I mean: there was some waves on the screen before starting the RFSniffer command. Then, Piscope seemes a good application but I did'nt found any guide to understand how to use it (zoom, stop service, save as file etc) does it's normal the pgpio 27 was 'creating' waves before starting to sniff?
    – onec0de
    Jan 28, 2019 at 13:26
  • For Joan to get a notification that you have responded to her comment you have to use an @ symbol before her name which does this @joan
    – T. M.
    Mar 3, 2019 at 9:44

1 Answer 1


First of all: Yes, it is possible that your device is not sending at 433MHz, since other frequencies are written on it. Different countries have different regulations on different frequencies, so there are devices which could send on different frequencies.

There are several possible problems here.

433MHz is not a single frequency, it is a frequency band with a (not so large) frequency range. Transmitters can send on one of the frequencies, like radio stations. Their transmitter listens on that frequency, just like a radio.

Then, there are many ways to transmit data.
The most simple one for 433MHz is to switch the sender on and off (ASK, Amplitude Shift Keying). Compare this to AM radio where the sender sends on a fixed frequency, and varies amplitude to transmit sound. The problem is: When the sender is far away, one hears lots of noise, especially when there is silence in the sound. However, this is how the majority of devices communicate.

A more advances transmitting technique is to keep the sender on, but change between two frequencies (FSK, Frequency Shift Keying). This is like FM radio. Think about: If there is no radio station on the selected frequency, you hear loud noise, but once you tune to a station, the sound is very clear, and even silence is real silence. The quality is much better here, even if the station is far away.

Now, back to your 433MHz receiver.
As a very cheap one, it can not tune to a specific frequency, but receives the entire band. It is possible that it doesn't receive a weak sender, like it's hard to understand a quietly speaking person in some distance on a party. Solution: Put the sender next to the receiver. And since the receiver is of the ASK type, it can not receive a FSK sender. A FSK sender appears as "always on".

Next: If you don't hear anything on the radio, you increase volume until you hear noise. If then there is a transmission, it's very loud, and you decrease volume, until it's ok. If the transmission is over, well, YOU would keep the volume setting since you expect the next transmission at the same level. The receiver always increases volume slowly until it "hears" something, even if it's noise.
If you look at your GPIO with Piscope, you should see a stream of random ones and zeros. As soon as something is received, you should see some pattern. This is the prove if your receiver is properly working.

If it does, it's still possible that RFsniffer does not understand the pattern sent by your sender, like you don't understand every language. There are common standards out there, but some senders implement their own, and then, RFsniffer is lost.

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