How to Configure WSJT with PowerSDR and VAC

How to Configure WSJT with PowerSDR and VAC 

System Dependencies
Minimum PowerSDR Version: 1.14.0
Applicable Hardware: All transceivers

Content provided by: Tim, W4TME

The intent of this article is to describe in detail the setup and configuration of WSJT with PowerSDR.  The configuration of WSJT‘s parameters other than the audio and PTT are out side the scope of this article.

Configuration Overview and Required Software 
Configuring WSJT for PowerSDR is a five (5) step process.  In this procedure we are assuming that you have your software defined radio and PowerSDR properly communicating and are using the most current versions of PowerSDR.  This procedure was developed using the FLEX-5000, so it is important that you have the latestFirewire driver and firmware loaded for your radio as well.

Step 1. Download and install the latest version of WSJT 
You can download WSJT software from the WSJT home page .  For this procedure, WSJT 7.02 was used.

Step 2. Download, install and configure a virtual com port software (Com0Com or VSPmanager) for PTT Control 
Although there are several different free software packages for enabling virtual com ports, I have prefer to use Com0Com or VSPmanager because they provide better control over the com port configuration, the configurator works under Vista and Win7 (vCom does not) and they come in a 64-bit and 32-bit version.  You can download the virtual com port software from the Com0Com SourceForge project page . For this procedure Com0Com was used. The VSPmanger software along with configuration documentation can be obtained from the K5FR web site.

Step 3. Download, install and configure the Virtual Audio Cable software (VAC
VAC is a program that transfers the RX audio from PowerSDR to WSJT and subsequently transfers the TX audio from WSJT to PowerSDR without using a physical interface between the radio and a computer sound card.  VAC makes PowerSDR “look” like a sound card or Windows audio device to WSJT. The benefit of VAC is that the audio exchanged between PowerSDR and WSJT stays entirely in the digital domain resulting in high dynamic range signals and there are no wires to introduce RFinto the software defined radio system.

VAC is not free open source software.  It must be purchased from the authors web site.  There is a demo version of VAC but it can not be used because the demo version corrupts the audio I/O with a pre-recorded voice telling you it is demo software, essentially making it crippleware.  For this procedure, VAC 4.09 (4.90) was used. 

NOTE: Some earlier version of VAC less than 4.08 have been known not to work properly with WSJT.

Step 4. Configure PowerSDR to use VAC and Com0Com to interface with WSJT 
Once the required software is downloaded and installed on your computer, the next step is to configure PowerSDR to use the VAC virtual audio cable for audio transfer and to configure a PTT line so that WSJT can key the transceiver.  For this procedure PowerSDR 1.14.0 was used.

Step 5. Configure the Audio and PTT ports in WSJT 
The final step is to configure PTT control and the audio input and output connections for WSJT.  This is probably the most confusing part of the WSJT configuration since the audio setup interface is very rudimentary.

Step 1. Download and install the latest version of WSJT 
Using the URL listed above in Step 1 of the Configuration Overview and Required Software section for the WSJT home page download and install WSJT.  As of the date of this article, WSJT 7.0.2 (r383) is the released version of the software.

The installation instructions for WSJT are located in the WSJT6 User Guide and Reference Manual that can be downloaded from the WSJT web site’s documentation pages.   There are translations of this manual in several different languages.

For additional information regarding the installation and initial setup of WSJT, please see The Complete Bozo’s Guide to HF JT65A (a work in progress) by Andy K3UK.  This is a very comprehensive, well written and humorous guide for setting up WSJT for HF using the JT65A mode of operation.

For additional information, it is recommended that you visit the HF Link home page where there is a detailed description of how to operate JT65

Step 2. Download, install and configure a virtual com port software Com0Com for PTT Control 
If you are unfamiliar with the concept of virtual com port pairs that are sometimes called virtual null modem cables, you can refer to the Knowledge Center article,What is a virtual com port or null modem emulator? , for a detailed description of how virtual com port software works.

As noted above, in this example, Com0Com virtual com port software is used.  You can refer to this Knowledge Center article, Virtual Serial Port Driver (com0com)for additional information about Com0Com.

Using the Knowledge Center article, Com0Com Installation and Configuration Guide , download and execute the instructions for obtaining the Com0Com software, installing, configuring and optimizing a virtual com port pair.  For this configuration only one pair is required.  I have configured my virtual com port pair as 8/18.

Step 3. Download, install and configure the Virtual Audio Cable software (VAC
As noted above, you must purchase VAC as it is a commercial product.  Using the URL listed above in Step 3 of the Configuration Overview and Required Softwaresection for the VAC home page you can purchase your copy of VAC if you have not already done so.  If you have VAC 4.x, but it is not version 4.09, you are entitled to get minor version upgrades.  To get them, you must contact the company or software distributor from whom you purchased VAC from initially as the upgrades are not directly available from the VAC home page.  This procedure has not been tested with the 3.x version of VAC and some older versions of VAC 4.x have been reported not to work for whatever reason.

The VAC package is distributed as a ZIP archive. Simply unpack it into an empty folder, run setup.exe application and follow the instructions displayed. If you are installing VAC for the first time, please review the readme.txt and vac.chm (Windows Help) files before installation. If you have already installed previous version ofVAC 4.x, don’t forget to uninstall it before installation.

Using the Knowledge Center article, How to Setup Virtual Audio Cable (VAC) 4.0x with PowerSDR 1.x , execute steps 1 through 3 for the instructions to configure the two (2) VAC audio cables.  The instruction in the KC article represent a very “conservative” configuration.  For the WSJT configuration, we will use a more optimized configuration.

Make the following changes: 

  1. Ms per Int = 5
  2. Stream Fmt = Cable Range
  3. BPS = 8 .. 16

Step 4. Configure PowerSDR to use VAC and Com0Com to interface with WSJT 
Configure the PowerSDR sampling rate to 96 KHz and the audio buffers to 1024 .  Make sure the FLEX-5000 Firewire device driver is set to  the same parameters andSafeMode 1 is the operating mode.  If you are unsure how to do this operation, refer to the Knowledge Center article How to Configure Hardware Sampling Rate, Hardware Buffers and Operation Mode in the FLEX-5000 Control Panel.

Using the same Knowledge Center article referenced in Step 3, How to Setup Virtual Audio Cable (VAC) 4.0x with PowerSDR 1.x , execute steps 4 through 6 of the instructions to configure the PowerSDR VAC Audio parameters.  As with Step 3, we need to modify the default configuration to a more optimized one for WSJT.

Make the following changes: 

  1. Driver = Windows WDM-KS
  2. Virtual Audio Cable Setup (Input) = Virtual Cable 1
  3. Virtual Audio Cable Setup (Output) = Virtual cable 2

NOTE: Do not worry about the TX and RX Gain (dB) values, those will be set later 

Configure PowerSDR to use a com port for external keying by configuring.  PowerSDR will use the virtual com port 18 of the virtual comport pair 8/18.

  1. Start PowerSDR and open the Setup form
  2. Select the CAT Control tab.
  3. In the PTT Control section, click on the drop down box and select the virtual com port of the virtual com port pair defied previously in a step above.  In this example I used COM18.
  4. Check both the RTS and DTR check boxes.
  5. Check the Enable PTT check box.
  6. Check on the Apply button and close the Setup form

Step 5. Configure the Audio and PTT ports in WSJT 
First, we will set up the PTT port for WSJT since that is the most straightforward process.

PTT Port Configuration 

  1. Start WSJT
  2. From the main WSJT window (GUI), left click on Setup and choose Options
  3. In the Station Parameters Section, enter , the other half of the 8/18 virtual com port pair defined previously.

Now comes the part that isn’t so intuitive; setting up the audio input and output channels in WSJT 

Audio Channel Configuration 
When WSJT is started, Windows command window (aka “dos” box) is displayed that shows all of the audio devices configured on your computer.  There can be a lot of them.  The ones that concern us are the Virtual Cable 1 and Virtual Cable 2 which are the VAC audio channels for PowerSDR.  See the screen shot below


What we have to do is set up WSJT so that the PowerSDR VAC output channel (Virtual cable 2 in this example) is configured to send audio to the WSJT INPUT channel .  Since the audio is bi-directional the PowerSDR VAC input channel (Virtual cable 1 in this example) must be configured to receive audio from the WSJTOUTPUT channel as well.

Using the display shown above, the WSJT input channels are devices numbered 0 to 4 ( NOTE: audio devices 0-4 have “0” output channels ).  Since the PowerSDRVAC output ( VAC virtual cable 2 ) needs to be directed to the WSJT input , we need to select audio device for the WSJT input .

Again, using the display shown above, the WSJT output channels are devices numbered 5 to 10 ( NOTE: audio devices 5-10 have “0” input channels ). Since thePowerSDR VAC input ( VAC virtual cable 1 ) needs to receive audio from the WSJT output, we need to select audio device for the WSJT output .

  • WSJT Input = VAC Output (virtual cable 2) = Audio Device #4
  • WSJT Output = VAC Input (virtual cable1) = Audio Device #9

===>>> Do NOT use the audio channels labeled FlexRadio Flex-5000 Audio or  FlexRadio Flex-5000 SPDIF/AC3 .  

Now that we know (hopefully) what audio devices are required, we have to set them up in WSJT:

  1. Start WSJT
  2. From the main WSJT window (GUI), left click on Setup and choose Options
  3. Enter the number in the Audio In Station Parameters data entry field
  4. Enter the number in the Audio Out Station Parameters data entry field
  5. Close the Options dialog box and shut down WSJT
  6. Restart WSJT
  7. Verify that the devices listed in the “Will Open Devices” line reports Input=4 and Output=9 (See the screen shot above)

NOTE: The ordering of the audio devices is not permanent.  Adding or changing an audio device on your computer WILL change the number associated with the audio device requiring you to set the audio channels up again

To test the configuration, start up PowerSDR and WSJT in this manner 

  1. Start PowerSDR
  2. Switch to DigiU mode and make sure VAC is enabled
  3. Start WSJT
  4. Confirm that the WSJT audio input and output device number are correct
  5. In the main WSJT window (GUI), click on the Monitor button.
  6. In the SpecJT window, you should see signal in the lower right hand corner bar graph.
  7. Adjust the PowerSDR VAC RX Gain until you achieve a signal input reading of between -4 and 0 dB.

If you do not see any output from PowerSDR in the SpecJT window, recheck that you have the WSJT audio channels setup correctly.  99% of the time this is the reason for not receiving any signals.