HowTo: Raspberry Pi – Output speech via FM signal

In the articles RaspberryPi – Install speech output with eSpeak and RaspberryPi – Send FM signals via GPIO pin is described how to use the RaspberryPi to read texts to the speaker and send FM signals. These two possibilities can be combined so that thanks to the RaspberryPi you are able to send readings via FM signals.

How to do it and what you have to keep in mind is described in the following article.

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Safety instructions

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Helpful Articles:
Before you start with this article, you should have prepared the RaspberryPi so far that it can be reached via the network and controlled by SSH. In addition, the voice output with “espeak” should already work and also the sending of FM signals.

The following three articles describe what to do to prepare the RaspberryPi:
RaspberryPi – Setting up for Nerdiys!
RaspberryPi – The first configuration
RaspberryPi – Controlling the RaspberryPi via SSH
RaspberryPi – Install speech output with eSpeak
RaspberryPi – Send FM signals via GPIO pin

Required tools:

Required material:

In the following list you will find all the parts you need to implement this article.

Important words in advance

Sending FM signals (and many others) over unauthorized radio transmitters is not legal in Germany and many other countries! The method shown below allows you to do just that. Please use it responsibly. Above all, make sure that you do not disturb regular radio stations. The method shown is comparatively powerful and radiates to even in other frequency range. That means that you can easily attract the displeasure of your neighbors and thus of the Federal Network Agency.

Log in via SSH on the RaspberryPi

To get started, you first need to log in to RasPi with SSH on Putty. How to do it is described in the article

After entering your username and password you can start to enter the first commands.

The command combination

To combine the speech output with the transmission of the FM signals, you must use the following command structure. The voice output from espeak is redirected via stdio and saved as a .wav file. Immediately thereafter, the fm_transmitter is called to play exactly this file and send it via FM. (Many thanks to Muhammet for the tip :))

You can read the text “Hello world, can you hear me?”(In command it is written in German “Hallo du große Welt da draußen!”) Of course it is possible to replace it with any other text. Also the FM frequency – as described in the article RaspberryPi – Send FM signals via GPIO pin – can be set to other frequencies.

espeak -vde "Hallo du große Welt da draußen!" --stdout> /tmp/tmp.wav && sudo /home/pi/fmtrans/fm_transmitter/./fm_transmitter -f 102.00 /tmp/tmp.wav

I hope everything worked as described. If not or you have any other questions or suggestions, please let me know in the comments. Also, ideas for new projects are always welcome. 🙂


P.S. Many of these projects - especially the hardware projects - cost a lot of time and money. Of course I do this because I enjoy it, but if you appreciate it that I share these information with you, I would be happy about a small donation to the coffee box. 🙂

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