Capturing and Recording Sound

If you happen to come across something particularly interesting or want to save a Morse Code transmission so you can practice later, you may be tempted to record the signal audio. This can be done in some webSDR radios. However, do be mindful of your local and regional laws regarding recordings. Please see the disclaimer link at the bottom of this page.

There are several ways to record sound on your computer or device. Though not all devices or computers are capable of doing this. Below are several methods that you can try.

webSDR site

The University of Twente site in The Netherlands has an Audio recording start button in the controls under the waterfall. Click on this button to start the recording. When you have what you need, click on the button again (which will now be named stop). At this point a Download link will appear and you can click on that to download a .wav file of what you heard. OpenWebRX based webSDR sites do not have any option to record a signal. If this is the case with the webSDR you are using, you can try one of the alternative methods below.

Record Device Speaker

This is simply taking a recorder and putting it up to the speaker of your computer or device, and recording the sound. If your computer or device has a built-in microphone, you could use that to record the sound.

If you want to use a decoder (to maybe decode Morse Code) on the captured sound, you need to record it in a way that you can save it to the computer or device that runs the decoder program. Most decoders work on the fly, meaning listening to what is played via the computer or device sound card so you'll need a way to play back the sound or to reroute the sound to the decoder program. If you save the sound on the computer, just run something to play it back while you have the decoder program running.

You could probably hook up your device or even the headphone jack of your computer to your computer's line in or microphone jack. Be warned that doing things this way can result in a low quality recording and could damage your computer or recording device! To help prevent damage, you'd need to buy a piece of hardware for your computer's microphone or line in jack (called an attenuator) and plug it into the computer's microphone or line in jack, then plug in the other end into the output (i.e. headphone jack of computer or device) into the attenuator. Be advised that if you do this with just your computer, you won't be able to hear any sound even though it's being fed back into the computer. Some computers let you "monitor" the microphone input so you could hear it through the speakers. For those that can't do this, you may need to invest in a Y-cable so that you can plug in the attenuator and a set of headphones or speakers into the output (headphone jack of computer or device).

Rerouting Sound

Another more reliable way to get a good recording is to reroute the sound back into the computer and record it. This involves setting a "loopback" in your computer's mixer settings and using sound recording software to record what is being played on the sound card. However, not all operating systems or computers are able to do this. Below are several methods you could try depending on your operating system. Keep in mind I don't know how to do this on ever device possible so if anyone does have a way for other systems, please contact me and let me know!

Linux

For the purpose of this tutorial, we'll assume you have a Desktop Environment installed such as KDE or GNOME, etc. Also be sure you have pulseaudio installed. I know for sure that Debian 9 with KDE has this pre-installed by default.

You will still need to download pavucontrol which is the pulseaudio mixer. Most mixers that are installed by default (i.e. the speaker icon in your system tray) does not always have all the controls you'll need to record sound from a web site.

At the terminal, type in:

$ sudo apt-get pavucontrol

This may also install other packages that are needed.

  1. First, start up your web browser and set it to the webSDR radio you want to capture the sound of.

  2. Run the pavucontrol program. You could type it in the menu search box to find it or look for VolumeControl in your Multimedia menu.

  3. In the Playback tab, click All Streams in the Show box at the bottom.

  4. Find your browser. If it's Chrome, then be sure the button on the Playback on is set to Simultaneous output to Built-in Analog Stereo. For Firefox it'll show up as AudioCallbackDriver and not have any options to set.

Other Operating Systems

Since I only use Linux, I do not know how to set up other operating systems. However, here are some links on the topic that may help you set up your own system:

If you are using a mobile device, you may want to search your app store for apps that would record what is being played on the device.