Raspberry PiRate Radio FM Transmitter

In November last year we posted a story showing how a Raspberry Pi could be used to transmit a digital AFSK signal to an RTL-SDR or other radio simply by connecting a wire to a GPIO pin.

Now an rtl-sdr.com reader has written in to let us know that this concept has also been used before to create a 1 – 250 MHz FM transmitter using the Raspberry Pi and a program called PiFM. It uses the same concept of connecting a wire antenna to one of the GPIO pins but modulates the frequency using hardware on the Rpi meant to generate spread spectrum clock signals. It is claimed that it can transmit up to 50m away.

Below we show an example YouTube video of the Raspberry Pi FM radio transmitting to an RTL-SDR running HDSDR.

PiFm & R820T & HDSDR


  1. Ed

    So I have hackers who are using this to introduce spoken word and music into my living space. Anyone ever encounter this?

  2. Dusan

    Did anybody tried making 2 way half duplex HAM radio transmitter with raspberry pi ? It should be fairly easy to transmit on 2m ham band, collect and amplify signal from raspberry pi, and than have sdr work on receiving end. Amplification/filter circuit shouldnt brake the bank

  3. Bob

    If you do this, scroll up the spectrum and see just how bad the harmonics are from this thing. In fact, if you transmit on the bottom end of the 1.25M band, you’ll find that any CDMA phones in the immediate vicinity will lose their connection to the local tower.

    • hydranix

      Bob is full of bullshit. Tested with 3 CDMA cellular phones and there was no effect on signal, call quality, or wireless data throughput. Was confirmed with a radioshack trunking scanner that there was indeed a broadcast at the supposed frequencies.

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