What you need

• A SSB receiver or transceiver
• FreeDV GUI software (Download for macOS, Windows and Linux),

Connecting Your Radio

If you don’t have a built-in sound card for digital modes you can use the normal audio inputs and outputs of your radio. The same cables and hardware that you use for other digital modes that are based on PC programs will work with FreeDV, but you will need a second sound interface for the microphone and speaker connections to the FreeDV program. A USB headset of the sort used by gamers is all you need for the second sound interface.

System Requirements

FreeDV is officially supported on the following operating systems and versions:

• Windows: Windows 10 and later
• macOS: macOS Big Sur (11.0) and later (ARM and Intel)
• Linux: Ubuntu 22.04 LTS and later, Fedora 42 and later

While it may be possible to execute FreeDV on additional platforms and distributions (especially ones similar to ones currently supported), this is not guaranteed. Any bugfixes required for an unsupported platform may be deferred or rejected, especially if there is impact to supported platforms. Requests for official support of new platforms should go through our existing Feature Request process.

Easy Setup

Upon starting FreeDV for the first time, the Easy Setup dialog will appear. This is a streamlined setup process for FreeDV optimized for hardware commonly used by amateur radio operators and is divided into three sections:

1. Sound card configuration,
2. CAT/PTT control, and
3. Reporting.

These sections are shown below:

Note that you can always return to this dialog by going to Tools – Easy Setup.

Sound Card Configuration

To configure your sound card(s) using Easy Setup, simply select the sound device associated with your radio and the microphone and speaker devices you wish to use to hear decoded audio as well as to transmit audio. If you’re setting up a receive-only station, you can choose “None” for the transmit audio device.

Additionally, if you are using a Flex 6000 series radio on the Windows platform, FreeDV will automatically select the DAX TX sound device. It is necessary only to select the correct “slice” for the radio sound device and the two devices to use for analog receive and transmit (e.g. your computer’s built in microphone and speaker devices).

Note that some configurations (for example, SDR setups involving multiple radio sound devices) may not be able to be configured with Easy Setup. For those, you can choose the “Advanced” button. You will see a more complex audio configuration window with the ability to test audio in and out. Do try Easy Setup first though.

CAT/PTT control

Easy Setup supports three methods of radio control:

1. No radio control (e.g. using a VOX audio device such as SignaLink),
2. Hamlib CAT control, and
3. Serial port PTT control.

Simply select the option that matches your radio setup and the required fields will appear. For Hamlib, these are typically the type of radio you’re using as well as the serial port it’s connected to (or TCP/IP hostname:port). Serial port PTT control requires the serial port your radio is using as well as whether your radio’s PTT is triggered via the RTS or DTR pin (and the required polarity for either).

If required, the “Advanced” button in this section will allow you to configure PTT input (e.g. for a footswitch) and additional VOX related options. The “Test” button will emit a constant carrier on the selected radio sound device as well as enable PTT to allow you to adjust your radio sound levels (see “Sound Card Levels” below).

Reporting

While not required, it is recommended to enable reporting so that others can see who is currently receiving them. This also allows the FreeDV application to control the radio’s frequency and mode. Both sides of a contact must have this enabled in order for contacts to be reported. To configure reporting, simply enable the feature here and enter your callsign and current grid square/locator.

Sound Card Levels

Sound card levels are generally adjusted in the computer’s Control Panel or Settings, or in some cases via controls on your rig interface hardware or menus on your radio. In-app adjustments can also be done by using the ‘TX Level’ slider at the bottom of the main screen; anything below 0 dB attenuates the transmit signal.

When FreeDV is running, you can observe the sound card signals in the main window tabs (From Radio, From Mic, To Speaker).

1. On receive, FreeDV is not very sensitive to the From Radio level, adjust so it is mid-range and not clipping. FreeDV uses phase shift keying (PSK) so is not sensitive to amplitude.
2. The transmit level from your computer to your radio is important. On transmit, adjust your level so that the ALC is just being nudged. More is not better with the FreeDV transmit signal. Overdriving your transmitter will lead to a distorted transit signal, and a poor SNR at the receiver. This is a very common problem.
3. FreeDV can drive your transmitter at an average power of 40% of its peak power rating. For example 40W RMS for a 100W PEP radio. Make sure your transmitter can handle continuous power output at these levels, and reduce the power if necessary.
4. Adjust the microphone audio so the peaks are not clipping, and the average is about half the maximum.

Rig Audio Processing

FreeDV likes a clean path through your radio. Turn all audio processing OFF on transmit and receive:

• On receive, DSP noise reduction should be off.
• On transmit, speech compression should be off.
• Keep the receive audio path as “flat” as possible, no special filters.
• FreeDV will not work any better if you band pass filter the off air received signals. It has its own, very tight filters in the demodulator.

Notes for specific radios

• Icom
• Yaesu
• Kenwood
• QRP-Labs QMX

Microphone level

A good microphone, faily close to your mouth, at a good level makes a huge difference to how you sound over digital voice.

When you transmit you’ll see a waveform display called “Frm Mic”. The level should average about 0.5 in general and you should avoid clipping or consistently low level.

Since FreeDV 2.0.2 there has been a microphone automatic gain control (AGC) enabled by default in the Filter window. This can help keep your levels right but tends to have a slow initial attack time.

USB or LSB?

On bands below 10 MHz, LSB is used for FreeDV. On 10MHz and above, USB is used. After much debate, the FreeDV community has adopted the same conventions as SSB, based on the reasoning that FreeDV is a voice mode.

As an aid to the above, FreeDV will show the current mode on the bottom of the window upon pressing the Start button if Hamlib is enabled and your radio supports retrieving frequency and mode information over CAT. If your radio is using an unexpected mode (e.g. LSB on 20 meters), it will display that mode on the bottom of the window next to the Clear button in red letters. When a session is not active, Hamlib isn’t enabled, or if your radio doesn’t support retrieving frequency and mode over CAT, it will remain grayed out with “unk” displaying instead of the mode (for “unknown”).

Which mode?

The latest mode, RADE, uses machine learning to significantly improve on the performance of the earlier modes. RADE sounds more natural and performs better in low signal to noise conditions. Earlier modes, such as 700D, have been kept in the FreeDV app for compatibility with hardware such as EzDV and SM1000 which cannot run RADE.

Specific notes for Icom users.

Troubleshooting

Radio control not working	CAT control over serial issue. Is the right serial port selected? Do other apps such as WSJT-X and Fldigi work?
Radio control unreliable on Linux	There may be other software attempting to use serial ports. Refer to the user manual about this.
No RF out on transmit	Radios with USB connection such as IC-7300 should be in LSB-D or USB-D and Digital Mic should be set to USB (Universal Serial Bus) input.
Low microphone level	Adjust audio gain in the main window and in the operating system’s sound settings.

For much more detail about the FreeDV GUI application please refer to the user manual.

Need help?

A great place to get help and learn from the experience of others is the digitalvoice Google Group.

Joe, VK3SRC, has a helpful page on the sarcnet site here.