RF transmitter for Raspberry Pi
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Latest commit 1423af8 Mar 22, 2018

README.md

rpitx is a radio transmitter for Raspberry Pi (B, B+, PI2, PI3B,PI3B+,PIZero,PiZerow) that transmits RF directly to GPIO. It can handle frequencies from 5 KHz up to 1500 MHz.

Before you transmit, know your laws. rpitx has not been tested for compliance with regulations governing transmission of radio signals. You are responsible for using your rpitx legally.

Rpitx is now based on a general Radio Frequency library : https://github.com/F5OEO/librpitx

Created by Evariste Courjaud F5OEO. Code is GPL

Installation

Assuming a Raspbian Lite installation (stretch) : https://www.raspberrypi.org/downloads/raspbian/

git clone https://github.com/F5OEO/rpitx
cd rpitx
# make sure to have access to the internet to download packages
# or download and install them manually (libsndfile1-dev and imagemagick)
./install.sh

Hardware

Plug a wire on GPIO 4, means Pin 7 of the GPIO header (header P1). This acts as the antenna. The optimal length of the wire depends the frequency you want to transmit on, but it works with a few centimeters for local testing.

Short manual

General

rpitx is the main software to transmit. It allows to transmit from:

  • IQ files *.iq (can be generated by external software like GNU Radio).
  • Frequency/Time files *.ft (generally used to easily implement digital modes)

Usage:

rpitx [-i File Input][-m ModeInput] [-f frequency output] [-s Samplerate] [-l] [-p ppm] [-h]
-m            {IQ(FileInput is a Stereo Wav contains I on left Channel, Q on right channel)}
              {IQFLOAT(FileInput is a Raw float interlaced I,Q)}
              {RF(FileInput is a (double)Frequency,Time in nanoseconds}
              {RFA(FileInput is a (double)Frequency,(int)Time in nanoseconds,(float)Amplitude}
               {VFO (constant frequency)}
-i            path to File Input
-f float      frequency to output on GPIO_18 pin 12 in khz : (130 kHz to 750 MHz),
-l            loop mode for file input
-p float      frequency correction in parts per million (ppm), positive or negative, for calibration, default 0.
-d int        DMABurstSize (default 1000) but for very short message, could be decrease
-c 1          Transmit on GPIO 4 (Pin 7) instead of GPIO 18
-h            help (this help).

Modulation samples

Some modulations are included in this repository and can be easily extended. These scripts create files which can be used by rpitx. Some output in IQ (like SSB) other in FT (like SSTV).

Single Side Band modulation (SSB)

pissb converts an audio file (Wav 48KHZ mono only!) to SSB (Upper Side Band right now) and outputs it to an IQ file. Assuming your audio file is in your current working directory:

./pissb audio48mono.wav ssbIQ.wav

You could then transmit it on 50MHz (please set a correct frequency to be legal)

sudo ./rpitx -m IQ -i ssbIQ.wav -f 50000 -l

A sample script testssb.sh is included.

Broadcat Frequency Modulation (FM)

pifm converts an audio file (Wav) to broadcast FM using Christophe Jacquet (F8FTK) PiFmRds project fork : https://github.com/F5OEO/PiFmRds

See Readme from this project for instructions.

Slow Scan Television (SSTV)

pisstv converts an RGB picture to a SSTV .ft file. The SSTV module will transmit using the Martin M1 encoding mode.

If you have a JPEG picture 320x256 you can convert it to an RGB picture with:

imagemagick convert -depth 8 picture.jpg picture.rgb

You can then transmit on 144.5Mhz (please set a correct frequency to be legal) :

./pisstv picture.rgb 144.5e6

A sample script snapsstv.sh grabs a picture from a PiCamera and then transmits it on 144.5 MHz.

Fast Simple QSO (FSQ)

pifsq allows to send a text with the new FSQ modulation

It is still under development.

A sample script testfsq.sh allows to send a text with FSQ

Weak Signal Propagation Reporter (WSPR)

wsprrpi allows to send wspr beacon https://en.wikipedia.org/wiki/WSPR_(amateur_radio_software) It uses a fork from James (https://github.com/JamesP6000/WsprryPi) project and adpated to librpitx for frequency ehancement and cleaner spectrum (to be confirmed)

See https://github.com/F5OEO/WsprryPi for instructions

Variable Frequency Offset (VFO)

A VFO mode is provided to allows precise frequency resolution. For example to set a carrier on 100MHz (please set a correct frequency to be legal)

sudo ./rpitx -m VFO -f 100000

Notes

All rights of the original authors reserved. Special thanks to Sylvain Azarian F4GKR for improving SSB modulation Inspired by