Direwolf notes

Installation on debian based distros

Install prereqs: libasound2-dev, xastir, ax25-tools, ax25-apps, git and audacity

Audacity is being used as a quick and cheerful method to see the audio levels coming from the sound card to make sure it isn’t spiking or distorted. Run the below command in a terminal window.

sudo apt-get install libasound2-dev xastir ax25-tools ax25-apps git audacity

We’re going to pull down the source for Direwolf and compile it on the computer locally. If you’re not sure about what you’re doing, copying and pasting the below lines into the terminal will be enough to get everything running.

cd ~  
mkdir git  
cd git  
git clone https://www.github.com/wb2osz/direwolf  
cd direwolf  
make  
sudo make install  

Direwolf Configuration

Before attaching the USB sound card, run the below command in a terminal window to see what your setup looks like as it is. The below command lists playback devices.

aplay -l

My output:

sj@x230:~/Downloads$ aplay -l  
** List of PLAYBACK Hardware Devices **
card 0: PCH [HDA Intel PCH], device 0: ALC269VC Analog [ALC269VC Analog]  
  Subdevices: 1/1  
  Subdevice #0: subdevice #0  
card 0: PCH [HDA Intel PCH], device 3: HDMI 0 [HDMI 0]  
  Subdevices: 1/1  
  Subdevice #0: subdevice #0  
card 0: PCH [HDA Intel PCH], device 7: HDMI 1 [HDMI 1]  
  Subdevices: 1/1  
  Subdevice #0: subdevice #0  
card 0: PCH [HDA Intel PCH], device 8: HDMI 2 [HDMI 2]  
  Subdevices: 1/1  
  Subdevice #0: subdevice #0  

Then attach the USB sound card and run the same command again. Look out for the change as this is what you’ll need to take note of for Direwolf to capture and output audio.

My output:

sj@x230:~/Downloads$ aplay -l  
** List of PLAYBACK Hardware Devices **  
card 0: PCH [HDA Intel PCH], device 0: ALC269VC Analog [ALC269VC Analog]  
  Subdevices: 1/1  
  Subdevice #0: subdevice #0  
card 0: PCH [HDA Intel PCH], device 3: HDMI 0 [HDMI 0]  
  Subdevices: 1/1  
  Subdevice #0: subdevice #0  
card 0: PCH [HDA Intel PCH], device 7: HDMI 1 [HDMI 1]  
  Subdevices: 1/1  
  Subdevice #0: subdevice #0  
card 0: PCH [HDA Intel PCH], device 8: HDMI 2 [HDMI 2]  
  Subdevices: 1/1  
  Subdevice #0: subdevice #0  
card 1: Device [C-Media USB Audio Device], device 0: USB Audio [USB Audio]  

The device listed as USB Audio Device is what I’m looking for here. Yours might state a brand or model name. The two things we are taking note of are the card number and the device number. In my case, 1 and 0.

You can also run the below to check the recording device, but this usually matches the same as what is shown for the playback device.

arecord -l

Right now we’ll configure Direwolf as read only and can add to the configuration later on to increase functionality. Open up direwolf.conf in your home directory using your favourite text editor. If you can’t see it in the home directory, it may be in ~/git/direwolf. You can either switch to that directory and edit the file within there or move it to another location. For ease of use, I keep direwolf.com in the root of my home directory.

Change MCALL NOCALL to MYCALL YOUR-CALL-SIGN and add -10 at the end. So for example MM6LOL-10. The “-10” is a SSID used to show you are operating on this device from a static, home station in my case. You can find other SSIDs here.

MYCALL MM6LOL-10

Remove the # from ADEVICE so that it looks like the below. If the output noted from “aplay -l” was 1 and 0, you can leave the rest as it is. If it differs, change the numbers to match what you noted. Enter the card number first, followed by the device number.

ADEVICE plughw:1,0

Save and close the file. That should be enough to get everything up and running as read only.

Checking Audio Levels

Next we’ll want to connect the output of your radio to the mic input of your soundcard. Once complete, open up audacity and check that the capture device is set to your USB sound card. The name should be the same as what the output from “aplay -l” showed.

In my case, I switch to a broadcast radio station to get a consistent output from the radio that we can use to confirm that the input isn’t peaking or distorting. Hit record. This will begin to show the output audio from the radio.

If you’re seeing something like the below, your audio levels are too high. This could be due to the system settings, but we’ll tackle this from the source first.

On the radio, turn down the volume till you see something like the below. It doesn’t need to be too loud for Direwolf to pick up on and we can fine tune later on.

Running Direwolf

To start Direwolf, simply open up a terminal or use the existing one you have open and type in the below. Make sure you’re operating from the directory direwolf.conf is in. Running direwolf without any additional switches causes the application to look for a config file in the directory you’re currently operating from.

direwolf

If you have the audio levels correct and you’re tuned into the 2M APRS frequency for your country (144.800MHz), you should start to see APRS packets being decoded and displayed in the terminal.

If you don’t see anything, unplug the audio cable from your radio and confirm that you are hearing APRS packets through the loud speaker.

If you are heading audio plug back in and adjust the audio levels, waiting some time between each change as you may not be receiving a steady stream of packets depending on your location.

Tweaking Audio

Next we’ll analyse the audio levels that are reported by Direwolf.

If you look at my example above, the first line in each packet shows the audio level received by Direwolf.

MB7USI-1 audio level = 103(44/20) [NONE]

Direwolf recommends that the audio level for most packets should be around 50, where 103 is currently shown above. You’ll find that in most cases, this isn’t a problem till you get a prompt from direwolf under the audio level advising that you should reduce the audio levels.

I turn the volume down on the radio initially to bring as close to 50 as possible. If after playing about with the radio you still find levels aren’t as low as you want, we can start playing about with alsamixer.

From the terminal, type ‘alsamixer’ and hit return. You’ll see a GUI within the terminal showing various audio levels. Out of the box, this will show the devices default audio adapter. If you are using a USB device, you may need to switch to that device specifically by pressing F6 and selecting the USB device.

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Once you are controlling the correct device, press F4 to switch to the audio capture settings. You’ll see a bar, which can be manipulated by using the up and down arrow keys on your keyboard. Adjust this down slightly, press ESC on the keyboard and head back into Direwolf to see if the levels have dropped. If they haven’t dropped enough, repeat the steps above till you’re happy.