DISCLAIMER: Look into band pass filters (and why), here. Prior to experimenting, it is recommended to read up on local regulations.
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TX Audio Files Using pifmrds
Today we learn how to transmit audio files (.wav). Anyone can turn their Raspberry Pi into a radio transmitter! RPITX has all we need to turn a normal pi into our radio transmitter (see disclaimer at top)
If you have any questions at all, I'd love to hear them!
Example Video
RPITX
Previously, we walked through installation of RPITX, for anyone interested in setting it up from scratch
README.1st: Become Familiar With Local Regulations Before Attempting To Transmit Anything.
Additional Info: Getting RPITX
First, you need a Raspberry Pi (version 1-4).
Next, if installing, you can download from official RPITX here.
Example 'Antenna' Photo
The spiraling wire, taped around a drinking straw, is completely optional. Was originally a picture of a quick ant construction experiment (testing possible future antenna possibilities), and is not required.
A simple piece of ANY copper wire (harvested from ANY electronics trash devices) simply wrapped around the metal GPIO pin is all you really need!
TIP: smaller wire is recommended if experimenting according to local regulations (minimize distance)
GPIO Pin: A General Purpose Input / Output 'pin' is not committed to anything in particular. It exists to allow users to assign hardware, or create 'jobs' for it using software. You don't need to understand how any of this works to follow this tutorial! Still, I find definitions helpful.
Photo Closeup Raspberry Pi GPIO Pins:
As you can see above, there are many GPIO 'pins' available. This opens Single Board Computers up to many projects.
CREATING OUR ANTENNA (Attach To Pin 7 GPIO Header):
Optional: You can acquire breadboard / GPIO pin fitting wires from many sources. You don't even necessarily need this type of wire (but it does hook nicely onto GPIO pins).
Alternatively: cut a simple wire off any electronics device, strip a bit of rubber off one end, then twist the stripped copper end around the correct GPIO pin.
GPIO PIN: no matter your source of wire, the key is to hook or wrap around pin 7 GPIO header (for transmitting antenna).
If you would like to make an antenna similar to the one pictured above, grab yourself a straw, pencil, or other straightened part, and wrap a piece of wire around it. I doubled the length of mine by connecting an additional GPIO wire. This wasn't 'tuned' or designed for any purpose. Simply a result of current experimenting with the basic construction idea (and, it worked).
Next: Install RPITX To Raspberry Pi
(if you want to support this and get something neat / unique in return, see Privacybox image carries RPITX preinstalled in the "Extras" section)
For those who would like to install RPITX themselves from scratch, I walk you through that process here:
https://www.youtube.com/watch?v=DieexwiH9CA
RPITX allows you to turn an ordinary Raspberry Pi, into a full on Radio transmitter!
Simply add a random piece of wire (no special antenna of any kind needed here! Just small piece of wire!), and RPITX turns that wire into a transmitting antenna!
Recording Our Audio File
Tenacity is a fork of Audacity you may like to check out here.
Why Tenacity? See Post On Privacy Implications Of Audacity Buyout Here.
Tenacity is an open source fork created in response to changes in Audacity Privacy Policy.
Tenacity / Audacity: Use The Record Button
It's rather simple. Setup your microphone in preferences (if not built in). Then hit record.
Export To .Wav
After recording the audio you would like to transmit, follow the screenshot below to save that in WAV file format:
Transfer WAV File To Raspberry Pi Box
You can transfer your newly recorded audio from your PC, to your raspberry pi in a number of ways (usb, ftp, sftp, scp, wget / https)
I find scp (Secure Copy) the most straight forward, secure method (taking advantage of SSH access).
Example command below uses Kali linux. If using supporter image you will want to utilize your user account login (in place of kali).
scp tx-test-rec.wav [email protected]:/home/kali
The above command uses the format:
scp [filenameHere] login@hostIP:/home/usernameHomeDir
Substitute the above with your own login name, 'hostIP' (192.168.1.188 in example), and user home directory on the raspberry pi itself.
This tells scp where the file is going, and what user is logging in.
Screenshot:
Above we use the mentioned scp command and kali example. Supporter image will use the supporter image login.
Transmitting Audio File (.wav)
Now that our file is transferred, we can transmit our audio file!
Running the following (example) command transmits our recorded audio file FM on 434MHz ISM band.
Substitute where you may have license to transmit (look into your country local regulations)
TX Command (Transmit WAV)
./pifmrds -freq 434 -audio FileNameGoesHere.wav
Setup Up Listening
You can use one of the Baofeng radios I recommended followers here and here.
TIP: If you have one, a software defined radio (SDR) can be handy to observe signals
In the screenshot below, I am using GQRX on my Linux Tablet (Pine64 Pinetab). It has a built in SDR.
Received Signal Closeup
Video Example: TX + RX In Action
What are you going to make with RPITX?
Love to hear about it.
UPDATE: RPITX AUTHOR PRESENTATION ON TX
June 2022: hardware failure on video rendering machine. I will be purchasing new hardware for the failed storage device.
Help grow this community by Sharing links to tutorials here, or on the video channels.
Thoughts? Questions?
Comments Welcome.
What do you want to do with RPITX?