Digital modes (Linux)

Connecting digital mode applications to Web Radio Control

You need to have wrc-proxy helper application and the virtual audio cable installed before you can proceed with these steps. See the page Initial setup for using digital modes in Linux for installation instructions.

  1. Open the Web Radio Control remote control user interface

  2. Open the Settings windows and select the Hamlib proxy tab

    Open the Settings windows and select the Hamlib proxy tab

  3. If the list of proxy URL addresses already contains the radio, which you wish to use, skip to step 5

  4. Create a new proxy URL address

    • Select the radio you wish to control from the [select] drop-down menu

    • Click Create new Hamlib proxy connection for

  5. Click the Connect button next to the proxy address URL of the radio you wish to use to start the wrc-proxy helper application

    • Use the wrc-proxy application to open the wrc-proxy link in the web browsers

      Use the wrc-proxy application to open the wrc-proxy link in the web browsers

    • The wrc-proxy helper application will start up in a Terminal window. Leave the wrc-proxy helper application running in the background.

      Leave the wrc-proxy helper application running in the background

  6. Start the digital mode application you wish to use (e.g. WSJT-X or fldigi).

  7. Configure the digital mode application for Hamlib NET / rigctld protocol and use the address localhost:4532

    • There are detailed instructions below for connecting WJST-X to Web Radio Control

  8. Route audio between browser and the digital mode application with a virtual audio cable / loopback sound card. Read below for instructions for your operating system.

    • There are detailed instructions below for connecting WJST-X to Web Radio Control

You can monitor the audio signal transmitted by a digital mode application in Web Radio Control user interface by clicking Show audio and TX audio. This is how you can make sure that the audio signal is properly transferred between the web browser and the digital mode application.

Radio settings for digital modes

Most digital transmission modes require that the radio transmits the audio signal produced by the digital mode application as clean as possible, without the radio processing on altering the audio signal in any way.

To disable audio processing in a radio transceiver, all speech compression, auto-gain control and noise reduction features must be turned off.

The instructions below indicate recommended radio settings for running digital modes:

  1. Open the sidebar for radio settings in the Web Radio Control user interface

  2. Apply the following settings in the RF submenu:

    • RF POWER = 10 - 100% - many digital modes do not require using full RF power

    • RF GAIN = 100%

    • AGC = OFF, the FAST choice may also work well if the OFF choice is not available

    • PREAMP = 0db

    • ATTENUATOR = 0db

  3. Apply the following settings in the RX audio submenu:

    • NOISE BLANKER = off

    • NOISE REDUCTION = off

    • AUTO NOTCH FILTER = off

    • MANUAL NOTCH = off

  4. Apply the following settings in the TX audio submenu:

    • MICROPHONE GAIN = 50% - this may also affect transmit power, too much gain can distort the transmitted audio signal

    • SPEECH COMPRESSOR = off

    • VOX = off

Routing the audio signal between the web browser and the digital mode application

You will need to perform this routing procedure for audio signals between the web browser and the digital mode application every time you use the digital mode application.

The following instructions are for the PulseAudio sound system widely used in Linux.

  1. Start two-way (full duplex) audio streaming in Web Radio Control user interface by clicking the "Play" button

  2. Allow the web browser to use your microphone. When using Firefox, you must also choose the audio input used for transmitting audio. Choose Monitor of radio-input. The Chrome web browser does not ask you to select any audio input specifically. *NOTE! If the web browser does not ask permission to use a microphone, the choice to use a microphone may be stored in the web browser. You must remove this choice with Firefox. The section the web browser does not ask for permission to use the microphone below contains instructions on how to do this. Return back to this step after removing the microphone choice.

    • Firefox:

      Selecting the microphone or audio input in Firefox

    • Chrome:

      Allowing the use of a microphone or audio input in Chrome

  3. Start the PulseAudio application for routing audio called pavucontrol. The command-line command for starting the application is pavucontrol.

  4. Find the web browser audio output in the Playback tab of the pavucontrol application. This audio output is often the last one in the list. Click the button indicating the current audio device name and choose device radio-output so that the audio produced by the web browser will be routed to the loopback device (= virtual audio cable).

    • Firefox:

      Choose the audio output device for Firefox

    • Chrome:

      Choose the audio output device for Chrome

  5. Find the web browser audio input in the Recording tab of the pavucontrol application. This audio input if often the last one in the list. Click the button indicating the current audio device name and choose device Monitor of radio-input so that the audio produced by the digital mode application will be routed to the web browser and eventually to the radio.

    • Firefox:

      Choose the audio input device for Firefox

    • Chrome:

      Choose the audio input device for Chrome

  6. In the digital mode application (e.g. WSJT-X or fldigi), use the audio device Monitor of radio-output as the audio input device and the audio device radio-input as the audio output device.

    • See below for more detailed instructions for setting up WSJT-X

Problem: the web browser does not ask for permission to use the microphone

Web browsers may save the permission to allow microphone access and the selected microphone permanently per website. When using Firefox, it is necessary to remove this permission, so that it is possible to select another audio input device as the microphone. Chrome does not save the audio input device for the microphone, so the audio input selection needs to be done in the pavucontrol application and it’s not necessary to remove the permission for using microphone in Chrome.

Removing automatic selection of microphone audio input device in Firefox:

  1. Click the lock icon on the left side of the address bar

  2. Remove the permission for the website to use microphone by clicking the cross icon

  3. Refresh the page in the web browser

Removing saved permission to allow use of microphone in Chrome:

  1. Click the lock icon on the left side of the address bar

  2. Remove the permission for the website by selecting Ask (default) on row Microphone

  3. Refresh the page in the web browser

Case: Connecting WSJT-X to Web Radio Control

You will need to have the wrc-proxy helper application installed and connected to Web Radio Control according to the instructions above so that WSJT-X will be able to control the selected radio.

This section provides detailed instructions for connecting WSJT-X to Web Radio Control.

  1. Open the WSJT-X application

  2. Perform the following changes to radio control and audio settings

WSJT-X: Radio control and audio settings

  1. Open the Settings window via menu File > Settings…

  2. Select the Radio tab

  3. Apply the following settings

    • Rig: Hamlib NET rigctl

    • Network server: localhost:4532

    • PTT method: CAT

    • Mode: Data/Pkt — This is the recommended settings if your radio supports DATA mode for SSB

    • Split Operation: Fake It

  4. Click the Test CAT button and wait for the button to turn green, which indicates that the radio control connection is working

  5. Select the Audio tab

  6. Select the audio input and output devices

    • Input: radio-output.monitor with channel setting: Mono

    • Output: radio-input with channel setting: Mono

  7. Close the Settings window by clicking OK

Testing that the virtual audio cable works correctly

The digital mode applications should be able to process the received audio from the radio.

In WSJT-X, for example, the received audio should be visible in the WSJT-X audio waterfall spectrum and WSJT-X should be able to decode stations. If decoding is not working, check that the radio control works (e.g by changing the frequency band) and that the current frequency is correctly set for the digital mode in use. Verify also that the client computer clock is synchronized correctly, because many digital modes require the computer clock to be set very accurately.

You can monitor the audio signal transmitted by a digital mode application in Web Radio Control user interface by clicking Show audio and TX audio. This is how you can make sure that the audio signal is properly connected between the web browser and the digital mode application.

To verify that transmission works correctly in WSJT-X, for example, it is necessary to attempt a QSO with another station or to use the WSPR beacon mode. When WSJT-X is transmitting audio, you should be able to see the audio waterfall spectrum of the transmitted audio (usually a simple carrier wave) in the Web Radio Control waterfall scope when TX audio is selected.