P25 Trunked Tracking and Decoding with RTL-SDR, Unitrunker, and DSDPlus

Virtual Audio Cable

VAC takes audio from one application and pipes it into another application.


Go to http://software.muzychenko.net/eng/vac.htm.

Purchase Virtual Audio Cable and you will be sent an email with download instructions.  Save it in your Downloads folder.


Extract the vac414full zip file using the Windows compressed folder utility or 7-Zip. Right-click on the compressed folder and click Extract All.

Then click Extract.


A new window will open.

For Windows 32bit systems, double-click setup.

For Windows 64 bit systems, double-click setup64.

If you’re running as a standard Windows user, you will need the admin password.

If you don’t know which operating system you’re running, click the Start orb.  Click Control Panel.  With Category view enabled, click System and Security.  Click System.  It will be indicated under System, System Type.


Click Yes.


Click I accept.


Click Install.


Installation will begin.


Click Install.


Click OK.

VAC configuration


Click the Start orb.

Click All Programs.

Click Virtual Audio Cable.

Click Control Panel.

SR (sample rate) should default to 22050 – 48000.  BPS (bits per second) should default to 8 to 16.  NC (number of channels) change to 1 to 1.

Click Set.

Close Exit.


Click the Start orb.

Click Control Panel.

With Category view enabled, click Hardware and Sound.

Click Sound.

Playback tab should be selected.

If the Line 1 device is set as default (as shown here, with the green check mark), you do NOT want this.  Right-click your actual playback device (usually speakers) and click Set Default.

Click Line 1.

Click Properties.


Click the Levels tab.

Set the levels to 50.


Click the Advanced tab.

Under Default Format, select 1 channel, 16 bit, 48000 Hz.

Click OK.


Click the Recording tab.

Select Line 1.

Click Properties.


Click the Levels tab.

Set the level to 50.


Click the Advanced tab.

Under Default Format, select 1 channel, 16 bit, 48000 Hz.

Click OK.

Click OK on the Sound box.

Close the Control Panel.