Brad (AC0ZJ), Richard (KF5OIM) and I have been putting the pieces required for the new FreeDV 2020 mode, which uses LPCNet Neural Net speech synthesis technology developed by Jean-Marc Valin. The goal of this mode is 8kHz audio bandwidth in just 1600 Hz of RF bandwidth. FreeDV 2020 is designed for HF channels where SSB an “armchair copy” – SNRs of better than 10dB and slow fading.
FreeDV 2020 uses the fine OFDM modem ported to C by Steve (K5OKC) for the FreeDV 700D mode. Steve and I have modified this modem so it can operate at the higher bit rate required for FreeDV 2020. In fact, the modem can now be configured on the command line for any bandwidth and bit rate that you like, and even adapt the wonderful LDPC FEC codes developed by Bill (VK5DSP) to suit.
Brad is working on the integration of the FreeDV 2020 mode into the FreeDV GUI program. It’s going well, and he has made 1200 mile transmissions across the US to a SDR using the Linux version. Brad has also done some work on making FreeDV GUI deal with USB sound cards that come and go in different order.
Mark, VK5QI has just made a 3200km FreeDV transmission from Adelaide, South Australia to a KiwiSDR in the Bay of Islands, New Zealand. He decoded it with the partially working OSX version (we do most of our development on Ubuntu Linux).
I’m surprised as I didn’t think it would work so well over such long paths! There’s a bit of acoustic echo from Mark’s shack but you can get an idea of the speech quality compared to SSB. Thanks Mark!
For the adventurous, the freedv-gui source code 2020 development branch is here). We are currently performing on air tests with the Linux version, and Brad is working on the Windows build.
Reading Further
Steve Ports an OFDM modem from Octave to C
Bill’s (VK5DSP) Low SNR Blog
Really cool, have to once ask my neighbour to try it together as he has a big tower for hf in the garden and is also taking part in the local emergency radio operators club.
Does anyone know anything about the activities here in Europe?
Yes, really cool! Looking forward to testing the GUI version with Walter, K5WH here in the states.
That’s really great! I was trying to get mode2020 running on Ubuntu 18.04 last week, but get errors on cmake for installing LPCNet and also for including it into codec2. As I am a beginner in Linux and don’t understand these error messages, I will have to wait for the Windows version. But will be the optimal mode for the QO-100 satellite.
73’s Gerhard OE3GBB
Gerhard, we now have a build_ubuntu.sh script that takes care of the build process for you, see README.md in the branch above.
Hi David and all, just have successfully built freedv on my Ubuntu 18.04, using the new script. So I am ready for tests in mode 2020. Just have to configure a second soundcard and connect the linux computer to the radio. Will also do some tests via the QO-100 satellite later. Congratulations to all, how have contributed to this.
Well done Gerhard! We wrote that build script as it was getting hard for us to remember all the steps. You may notice sync is slow or drops out – that will be fixed soon. There is an all_2020.wav file in the freedv-gui/wav that you can use to test rx.
Hi David, there was just one link, that I had to install extra: canberra-gtk-module.
But I have problems wo configure the second sound card. Pls see my mail to freetel-codec2 about this.
73’s
Dear FreeDV developer, nice to meet you, I am an amateur radio station in Japan
My name is Hiro and I have a call sign JH0PCF.
I am with the same amateur radio team in Japan,
I am testing the software of FreeDV 2020
In order to expand it to more friends in the future,
It is necessary to know the detailed design more than the information that is currently published.
The information given to me is voice of 8 KHz bandwidth
It is possible to transmit at an RF bandwidth of 1.6 KHz
There is only information to say.
In the future, it will be FreeDV 2020 as a Japanese amateur radio companion
To introduce you to: https://freedv.org/
I need more information as described in the design of.
By all means, I sent an email asking you to teach me.
Thank you.
Hi Hiro,
Can you please give me an example of the information that you require?
Thank you for the reply
To introduce you to: https://freedv.org/
I want the following information written in
Design:
Codec 2 voice codec and FDMDV/COHPSK modems
1.25 kHz spectrum bandwidth (half SSB) with 75 Hz carrier spacing
FreeDV 1600 mode: 1275 bit/s voice coding, 25 bit/s text for call sign ID, 300 bit/s FEC, 16×50 baud DQPSK carriers, Differential QPSK demodulation
FreeDV 700(C) mode: 700 bit/s voice coding, no FEC, 14×75 baud QPSK carriers, frequency diversity to combat fading, coherent QPSK demodulation
Here is an example of 1600 mode
Modulation method, standards, etc.
Method FDMDV
Subcarrier modulation scheme 16DQPSK
Number of subcarriers 16 (DQPSK)
Subcarrier frequency interval 75 Hz
Data rate 1,600 bits / s (voice coding 1,275 bits / s, text 25 bits / s, FEC 300 bits / s)
Subcarrier transfer rate 50bit / s
CODEC CODEC 2
I would like similar information about FreeDV 2020.
Japanese amateur stations are not supposed to present the information
It is because the authorities do not allow them to communicate.
Thank you
Hi Hiro,
Ok so for FreeDV 2020:
31 QPSK carriers at 48.78 baud per carrier
Each carrier separated by 48.78 Hz
Pilot symbol assisted carrier recovery
Coherent QPSK demodulation
Raw data rate 3024.39 bits/s
LPCNet speech codec at 1733 bit/s
Rate 0.78 LDPC FEC code
Text at 22.22 bits/s
Cheers,
David
Please tell us the specifications of FreeDV 2020
Thank you very much.
It becomes a fellow of Japanese amateur radio by this
You can introduce it.
There is one more thing I would like to hear.
About the method.
The other 1600 modes include FDMDV as a method
There is FreeDV 2020 does not have that information yet
Can you tell me
The method is similar to the other modes. FDMDV stands for Frequency Division Multiplex over Digital Voice, and 2020 uses the same method