New Digital Voice Codecs for HF Ham Radio.....

Discussion in 'Survival Communications' started by BTPost, Apr 5, 2013.

  1. BTPost

    BTPost Stumpy Old Fart,Deadman Walking, Snow Monkey Moderator


    A new upgrade to FreeDV has been released. Amateur Radio Newsline's
    Heather Embee, KB3TZD has the details:


    FreeDV is a part of a ham radio developed digital audio system that
    should eventually allow just about any SSB radio and any computer
    operating system to be teamed together. This to enable transmission and
    reception of what developers call high quality narrow-band digital
    audio for the High Frequency amateur radio bands.

    To make this happen speech is compressed and then modulated onto a 1100
    Hz wide QPSK signal which is sent to the microphone input of a SSB
    radio_On receive, the signal is demodulated and decoded by the FreeDV

    The new upgrade called version dot 96 became available on March 23rd.
    It provides a 1600 bit-per-second mode that communicates at much lower
    signal levels than previously envisioned. As such, signals should be
    readable down to a 2 dB Signal to Noise Ratio, and long-distance
    contacts have already been reported using only 1 to 2 watts power. A
    compatibility mode for communication with the older dot 91 version is

    Developers say that an executable program for Windows is presently
    available. Also that Linux and other platforms will follow shortly.

    FreeDV was brought into being by an international team of radio
    amateurs working together on coding, design, user interface and
    testing. It is open source software, released under the GNU Public
    License version 2.1. The FDMDV modem and Codec 2 Speech codec used in
    FreeDV are also open source.
    3M-TA3 and DKR like this.
  2. DKR

    DKR Raconteur of the first stripe

    Thanks, sound like just the thing for my portable QRP rig!
    3M-TA3 likes this.
  3. techsar

    techsar Monkey+++

    CAUTION!!! Make sure the download is free of any virus before installing. This has been an issue encountered by a couple amateurs around here...ended up having to do full system restores.
    3M-TA3 likes this.
  4. DKR

    DKR Raconteur of the first stripe

    Thanks! I always scan everything before loading but its nice to know some stuff may be hiding in the code..
  5. DKR

    DKR Raconteur of the first stripe

    Not a necro - but a bit of an update rather than starting a new thread. FreeDV originally required a PC with 2 sound cards at each end of the radio circuit to be used.

    No longer. A FreeDv appliance is available - the SM1000.

    The SM1000 allows you to run FreeDV without a PC on any radio. Just plug it into your SSB or FM radio, and you now have Digital Voice (DV). You don't have to buy a new radio to run Digital Voice.

    It’s based on a STM32F4 micro-controller, has a built in microphone, speaker amplifier, speaker, and transformer isolated interfaces to your radio. It’s just 80 x 100mm, and can be held in you hand and used like a regular PTT microphone. Or it can sit on your bench and work with your favourite headset.

    The SM1000 was developed by David Rowe VK5DGR and Rick Barnich KA8BMA. It is being manufactured, tested and shipped by our good friend Edwin at Dragino in Shenzhen, China. The SM1000 is completely open - hardware and software - including the Codec 2 vocoder. You are encouraged to modify the software and hardware. It is possible to reprogram the SM1000 for other applications, such as speech processing for SSB radio using open source gcc tools.

    The rig audio and PTT connections are 3.5mm audio sockets in parallel with a RJ45. A small patch panel can be used to configure the RJ45 pin out for your radio. You need to supply audio cables, e.g. 3.5mm or RJ45 to your radio. The SM1000 operates from 8-16V (12V nominal) and uses approximately 200mW. Perfect for mobile or SOTA work! It also has a USB port to support reflashing from a Windows or Linux PC.

    So as new software is released, this appliance may be upgraded with the new software. All this for $195 each. It is compatible with a PC based systems, so a single unit is useful.

    While technically it is not 'secure' comms - that requires a pseudorandom, frequency hopping digital radio - it does provide for Very Low Probability of Intercept. The signal on a regular SSB radio sounds like background noise. To decode the signal requires specialized equipment. Since the code is 'open source' it is legal to use on the Ham bands in North America.
    ghrit and 3M-TA3 like this.
  6. DKR

    DKR Raconteur of the first stripe

    The SM1000 box demo

    75 meter QSO with today's bad band condx.

    2 way QSO over a ham sat.
    Last edited: Oct 30, 2017
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