Introduction

FreeDV beacon With repeat:

• Listens for FreeDV signals, then transmits a reply.
• Supports FreeDV 700D and 700E modes.
• Places the received signals as files.
• Requires a Linux machine with a sound card and RS232-PTT (or Hamlib CAT) interface to your radio.
• Just one sound card is required.
• Can run on machines as small as a Raspberry Pi.
• Now running with Codec2 API Ver 1.2
• Using Reliable Text, but we need extra chars for trigger string eg. + and -
• Since FreeDV cannot add these to a callsign, now triggering with numbers at the end of your callsign eg. VK2FABC0 or for short callsigns K1AA000
• With ideas like this, it's like having Talk Groups.

With Reporting off:

When a "trigger" string is detected in the rx FreeDV text message (e.g. "+" as in "+ de VK2ZZZ" ), the beacon will transmit your signal and an ident with BER stats back to you, that is, Reporting off. With Reporting on, edit your config and put 0-9 after your callsign. Max callsign length in FreeDV is eight. This software "looks" at positions 7 and 8. [Reporting] Enable=1 Callsign=VK2ZIW+ GridSquare=QF56HG

And then run FreeDV.

Freebeacon requires a "txfilename" wave file to transmit, e.g. some one saying "Hi, I am a FreeDV beacon blah blah". The signal report is encoded into the transmit text message. Make the wave file long enough so that the the signal report is sent at least once, say 5 seconds. Transmit will stop when the "txfilename" wave file is played once.

Freebeacon saves the received audio from the radio AND the decoded audio as wavefiles and as 700C files. Use "wavefilewritepath" to specify where they are written. The file name is a date and time stamp. The length is limited to 60 seconds. If you set "wavefilewritepath" to a listable webserver directory the files will be available for download on the Web. To avoid filling your file system write a cron job to clean these files up once a day.

If your input audio device is stereo note we only listen to the left channel.

If you have a RS232 serial port (specified with "-c") RTS and DTR is raised on transmit to key your transmitter, and lowered for receive.

If you are using Raspberry Pi you can use one of the GPIOs for PTT control of your transmitter using the "--rpigpio" option. You need to use the BCM GPIO number so "--rpigpio 11" uses pin 23 of the GPIO connector.

Note FreeDV 700C doesn't have a text channel, so not supported.

A whole lot of code was lifted from freedv-dev for this program.

Credits

• David Rowe, John Nunan
• Richard Shaw - CMake
• Bob Wisdom - Hamlib, FreeDV 700C & 700D modes
• Initially developed Dec 2015
• Refactored for GitHub, added Hamlib, FreeDV 700C & 700D modes in 2020
• Alan VK2ZIW for "repeat" May 2022

Building and Installation

1. Dependancies:

   sudo apt install git cmake sox libsamplerate0-dev portaudio19-dev libsndfile1-dev libhamlib-dev
   

2. Building Method 1 - installs codec 2 libraries on your system:

   Install codec2:

   git clone https://github.com/drowe67/codec2.git
   cd codec2
   mkdir build_linux
   cd build_linux
   cmake ../
   make
   sudo make install
   cd ../src; cp freedv_api_internal.h fmfsk.h /usr/local/include/codec2/.
   cp kiss_fft.h kiss_fftr.h varicode.h /usr/local/include/codec2/.
   

   Note: On my Ubuntu 18 and RPi I had to add an extra search path to the ld.conf.d directory to match the path the codec2 .so was installed in. sudo echo "/usr/local/lib" > /etc/ld.so.conf.d/local.conf sudo ldconfig

   Check it has found libcodec2.so using:

   ldconfig -v | grep codec2
   

   Build FreeBeacon:

   cd ~
   git clone https://github.com/drowe67/freebeacon.git
   cd freebeacon
   mkdir build_linux
   cd build_linux
   cmake ../
   make
   

3. Building Method 2 - without system wide codec 2 installation

   git clone https://github.com/drowe67/codec2.git
   cd codec2 && mkdir build_linux && cd build_linux
   cmake ../ && make
   

   Instruct freebeacon cmake to use local codec2 directory:

   cd ~
   git clone https://github.com/drowe67/freebeacon.git
   cd freebeacon && mkdir build_linux && cd build_linux
   cmake -DCODEC2_BUILD_DIR=~/codec2/build_linux ..
   make
   

4. Testing:

   Plug in your USB sound card and USB RS232 devices. Use alsamixer to adjust levels on your sound card. F6 lets you select sound cards

   Usage:

     ./freebeacon -h
   

   List sound devices

     ./freebeacon -l
   

   Example usage:

     ./freebeacon -c /dev/ttyUSB1 --txfilename ~/codec2-dev/wav/vk5qi.wav --dev 4 -v --trigger hello
   

   Testing your PTT by making it jump straght into tx mode:

     ./freebeacon -c /dev/ttyUSB1 --txfilename ~/codec2-dev/wav/vk5qi.wav --dev 4 -v --trigger hello -t
   

   Testing sound cards on RPi:

   Note: Make sure your user is in the group audio, otherwise you will see no audio devices:

   $ groups
   vk5dgr audio
   

   You can add your user to the audio group with:

   $ sudo addgroup vk5dgr audio
   

   Then see if you can detect record devices:

   $ arecord -l
     
     **** List of CAPTURE Hardware Devices ****
     card 1: Audio [RIGblaster Advantage Audio], device 0: USB Audio [USB Audio]
     Subdevices: 1/1
     Subdevice #0: subdevice #0
   
   $ arecord -D hw:1,0 -f S16_LE -r 48000 test.wav
   $ aplay test.wav
   

   Testing:

   As a first step try playing freebeacon_test.wav from another PC into the freebeacon machine input, this file has the trigger string "hello" in the txt msg.

How To Generate a FreeDV 1600 Modulated Wave file

The "sox" tool converts between the wav format and the raw audio samples freedv likes. The "sox" tool will need to be installed on your Linux machine. This might be easier on a desktop Linux machine but you could try it on a Pi too.

1. To generate the FreeDV 1600 modulated wav file prompt_1600.wav from the input voice wave file "prompt.wav":

   $ cd codec2/build_linux/src
   $ sox /path/to/prompt.wav -t .sw -r 8000 -c 1 - | ./freedv_tx 1600 - - |
   sox -t .s16 -r 8000 -c 1 - prompt_1600.wav

2. Test decode and playback on the default sound device:

   $ ./freedv_rx 1600 prompt_1600.wav - | aplay -f S16_LE