Mode FreeDV

FreeDV: open digital voice on HF.

Group	Amateur: voice & packet
Default frequency	14.236 MHz
Default sample rate	2 Msps
In the mode list	Digital voice, 14.236 MHz

Step-by-step: Tutorial-FreeDV

What FreeDV is

FreeDV is open digital voice for HF built around the codec2 vocoder.

Frequencies and settings

Setting	Value
Start frequency	14.236 MHz
Tuning range of the mode table	1 to 30 MHz
Sample rate asked	2 Msps
Lowest working rate	250 ksps
Channel width	3 kHz

OnAir takes any frequency you type; the numbers above are the mode's starting point and the range its table describes. In the app the shortcut label is Digital voice, 14.236 MHz.

What OnAir shows

FreeDV digital voice (700D, 700E, 1600) on upper sideband.

Tips and caveats

• Checked with generated signals and impairments; recordings of real signals welcome.
• Voice uses codec2, which comes with OnAir; nothing to install.
• Which radio: An RTL-SDR can receive HF only in direct-sampling mode, which OnAir offers in its radio settings; results depend on the antenna. SDRplay and Airspy HF+ radios are better suited.
• Try it without a radio: most modes include a built-in synthetic test signal, so you can open the screen and try the controls first.
• Receiving and the law: Amateur radio signals are meant to be received. Receiving needs no licence in most countries; OnAir does not transmit. Voice needs a codec library you install yourself. See Legal.

Related pages

• Voice codecs
• All modes, Amateur: voice & packet
• Supported radios, Troubleshooting, FAQ
• More in Amateur: voice & packet: M17, D-STAR, APRS (AFSK), LoRa APRS, MeshCom