27 March 2015


STANAG-4197 is  a NATO standard agreement indicated as "Modulation And Coding Characteristics That Must Be Common To Assure Interoperability Of 2400 Bps Linear Predictive Encoded Digital Speech Transmitted Over Hf Radio Facilities".
A description of the STANAG-4197 waveform can be found in radioscanner.ru, below a self-explanatory picture about the four parts of this signal:   

STANAG-4197 waveform (courtesy radioscanner.ru)
Data segment is sent on 16 channels at 75 Baud and channel separation 112.5 Hz (~112) while; voice segment is sent on 39 channels at 44.44 Baud and channel separation 56 Hz: both formed with OFDM technology.
This waveform is used in Advanced Narrowband Digital Voice Terminal (ANDVT or AN/DVT) modems that transmit encrypted digital voice over HF, these modems include the ANDVT MINTERM KY-99A modem. Sometimes you may found this signal under the ANDVT name, but it's wrong since STANAG-4187 is the waveform while ANDVT is the modem.

OFDM 16-tone data segment
OFDM 39-tones voice segment

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