Configure CWSkimmer with PowerSDR for Wide Band Operation

As noted previously, CWSkimmer is a program that decodes multiple CW signals all at the same time. It uses I/Q data streams for the decoding of multiple CW QSOs. PowerSDR v1.14.0 and later has the ability to send the digitized I/Q data stream generated by the SDR hardware directly to CW Skimmer via a VAC audio channel. This allows for wide-band reception of CW signals.


  • PowerSDR version 2.0 or greater.
  • VAC 4.09  or greater
  • PowerSDR must already be setup to operate CW with either a key or using the CWX (keyboard) form to send CW.
  • A virtual com port must be setup for CAT control. (Com0Com was used for this setup)
  • The CAT parameters must be setup in PowerSDR (port, baud rate, and number of stop, data and parity bits)

Third-Party Software Configuration

Before starting and configuring CWSkimmer, you must install and configure VAC for digital audio transfer and a virtual com port for CAT control. In this example, Com0Com is used for the virtual com port.

VAC Installation
Please refer to the HelpDesk article, How to Setup Virtual Audio Cable (VAC) 4.0x with PowerSDR for instructions on how to configure VAC.

NOTE: For this configuration, select the Windows WDM-KS driver in the PowerSDR VAC Cable setup described in step 6.

Com0Com Installation
Please refer to the HelpDesk article, Com0Com Installation and Configuration Guide, for detailed instruction on how to configure a virtual com port pair.

NOTE: You can also use VSPmanager for creating virtual com port pairs.

PowerSDR Configuration

Main Console
PowerSDR is setup in CW mode (U is preferred) with VAC enabled.

NOTE: Turn *OFF* Spur Reduction (SR) to prevent a 3 KHz variation in the CW Skimmer frequency readout.

Below is the PowerSDR console in CW mode configured for use with CW Skimmer.

Figure 1

Firewire Audio Configuration
Set the PowerSDR and Firewire sampling rate and buffers to 96 KHz and 1024 respectively.

VAC Configuration
After installing VAC and configuring two (2) audio "cables", start PowerSDR v1.14.0 and open the Setup form. Select the Audio->VAC tab. Configure the Audio-VAC settings as shown below.

Make sure the Direct I/Q settings are set correctly.


Figure 2


CAT Configuration
Start PowerSDR and open the Setup form. Select the CAT Control tab. In this example, I have created a Com0Com virtual com port pair 7/17. Configure the CAT Control settings as shown below.


Figure 3


CW Skimmer Configuration

Open CW Skimmer and click on the View menu option and select Settings...

Click on the Audio tab
For the Audio settings (Figure 4), set it up as shown below:

  • Soundcard Driver = WDM
  • Signal I/O = Virtual Cable 2
  • Audio I/O = Virtual Cable 1
  • Channels Left/Right = I/Q
  • Shift Right Channel Data by = 0 samples


Figure 4


Click on the Radio tab
For the Radio Settings (Figure 5), set it up as shown below:

  • Hardware Type = SoftRock-IF
  • Audio IF = 9600 (calculated from the 9000 Hz PowerSDR IF + 600 Hz CW sidetone offset = 9600 Hz)
  • Sampling Rate = 96kHz (same sampling rate as Firewire hardware driver),
  • CW Pitch = 600 (same as the Pitch frequency in PowerSDR CW Mode Controls - see Figure 1)


Figure 5

Click on the CAT tab
Select Use Radio 1 and click on the Configure... button

For the Rig 1 Settings (Figure 6), set it up as shown below:

  • Rig Type = PowerSDR
  • Port = Com 7 (the other half of the virtual com port pair)
  • Baud Rate = 9600 (matches the PowerSDR CAT parameter)
  • Data Bits =8 (matches the PowerSDR CAT parameter)
  • parity = None (matches the PowerSDR CAT parameter)
  • Stop Bits = 1 (matches the PowerSDR CAT parameter)
  • RTS = High
  • DTR = High
  • Poll Int, ms = 500
  • Timeout, ms = 4000


Figure 6

CW Skimmer In Operation:

Figure 7


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