rtlsdr-ft8d -- FT8 daemon for RTL receivers

WIP -- Need help for testing this project

(no stars, sad...)

TL;DR

This project aim at decoding FT8 signals using an RTL device, usually connected to a Raspberry Pi. To install and use your dongle on a Raspberry Pi with a Rasberian OS:

sudo apt-get -y install build-essential clang libfftw3-dev libusb-1.0-0-dev librtlsdr-dev libcurl4-gnutls-dev ntp
git clone https://github.com/Guenael/rtlsdr-ft8d
cd rtlsdr-ft8d
git submodule update --init --recursive
make
make install
rtlsdr_ft8d -f 2m -c A1XYZ -l AB12cd -g 29

Overview

This non-interactive application allows automatic reporting of FT8 messages on Internet. The inital idea was to allow a small computer like a Raspberry Pi and a RTL-SDR device to send FT8 reports for VHF/UHF bands. This kind of lightweight setup could run continuously without maintenance and help to get additionnal propagation reports. This code is just a glue between RTL libs and an FT8 open source library based on Karlis Goba (YL3JG) work.

This application written in C does:

A time alignment (15 sec, required NTPd to run on the OS)
Start the reception using the RTL lib
Decimate the IQ data (2.4Msps to 4000 sps)
Decode FT8 signals
Report any spots on PSKreporter
Repeat, again and again...

Installation

Install a Linux compatible distro on your device (ex. Raspbian for RaspberryPi)
Install dependencies & useful tools (for example, NTP for time synchronization). Example with a Debian based like Raspbian:
```
sudo apt-get -y install build-essential clang libfftw3-dev libusb-1.0-0-dev librtlsdr-dev libcurl4-gnutls-dev ntp
```

Clone this repository:

git clone https://github.com/Guenael/rtlsdr-ft8d
cd rtlsdr-ft8d
git submodule update --init --recursive

Build the application:
```
make
make install
```
Start the application with your right paramaters, ex. for the 2m band, with a fake callsign (A1XYZ):
```
rtlsdr_ft8d -f 2m -c A1XYZ -l AB12cd -g 29
```

Tips (for your Raspberry Pi and SDR dongles)

Use ferrite bead on the USB cable to limit the QRN
Use an external clean power supply
Cut off the display (could help to reduce QRN)
```
/opt/vc/bin/tvservice -o
```
Remove unused modules (for example, /etc/modules: #snd-bcm2835)
Use an enclosure, and ground it

Crystal stability

Most of RTL dongles use a cheap crystal, and frequency drift can effect the decoding & performance. The use of no-name RTL dongle for VHF/UHF bands usually require crystal modification, for a better one. External clock could be also used, like GPSDO or rubidium reference clock, aligned on 28.8MHz.

Some manufacturers intergrate a 0.5ppm TCXO. It's the best second option, after an external clock. Based on my personal experience:

NooElec NESDR SMART : Works fine out of the box
RTL-SDR Blog 1PPM TCXO : Works with some drift, require additional mass, or a better enclosure
Other no-name like : RT820, E4000, FC0012, FC0013, can work, but require modification and drift a lot

Ex: NooElec NESDR SMArt - Premium RTL-SDR w/ Aluminum Enclosure, 0.5PPM TCXO

https://www.nooelec.com/store/nesdr-smart.html

antonjan / rtlsdr-ft8d