Wednesday, August 21, 2013

Using the Funcube Dongle Pro+ with CW Skimmer

by Gabriel Sampol, EA6VQ

reproduced with permission of the author from  

Editor's note: The Funcube Dongle Pro + is a tiny and relatively inexpensive receiver that plugs into a USB port and is capable of 192-KHz coverage between 150 KHz and 1.9 GHz.  Because it does not blank out US cellular telephone frequencies, the DP+ is not legal for use in the United States.  For interested readers elsewhere, you can read more at the maker's website.


I got a Funcube Dongle PRO+ with the idea of setting up a secondary Reverse Beacon receiver for 28 and 70 MHz bands.  To my disappointment the current version of CW Skimmer (1.8) does not support this device so I have spent some time investigating how to make it work.

First of all I noticed that CW skimmer was recognizing it and it was receiving if I configured it as a Softrock with a 192 kHz Sampling Rate.

However, the frequency received had nothing to do with the value of  "LO Frequency, Hz". There was an offset all over the band.

I then realized that the shown frequency had to do with the last frequency set in the Funcube by another SDR program (SDRsharp) that I had used just before, so it was a matter of setting the right frequency with a program that supports the Funcube and setting that same frequency in CW Skimmer.
With this simple two-step procedure you can satisfactory use the Funcube Dongle PRO+ with CW Skimmer, and of course also use it for the Revese Beacon Network thru Aggregator.

This is an example on how to set the LO frequency to 28095 kHz, to cover the lower portion of the 10m band.

1. Download the FCHID (FCD+ Frequency Control Program) program for Funcube, place it in the CW Skimmer folder (for instance) and run it.  Set the frequency to 28095.

2. Set the LO Frequency to 28095 also in CW Skimmer, as shown in the first image.
And that's it.  You will be receiving the 27999 to 28191 kHz band and the frequencies shown in Skimmer will be correct.
No need to say that if you want to receive another band you will have to repeat both steps.

Well, now that I had it working I wanted to go one step further and find a way to switch bands automatically, so that I could monitor several bands sequentially. In order to it I obviously had to find a way to programmatically change the frequency in both, FCHID and CW Skimmer.

In order to change it in FCHID I developed a small program that uses Windows API calls. I called it ControlFCD and it accepts a frequency in kHz as a command line parameter (For instance "ControlFCD 28123" will change the Funcube frequency to 28123 kHz in FCHID).  No need to say that FCHID must be running when executing ControlFCD.

For changing the LO Frequency in Skimmer I didn't find a better way than changing this value in the CWSkimmer.ini and restarting the program so that i takes the new configuration file.  Instead of modifying the ini file I opted by creating different copies of the original file, each of which with the desired value of frequency, and copying then later over the CWSKimmer.ini.

Finally, I made a simple VBS to control the whole process of starting all the programs and automatically managing band changes at certain times. You can download this VBS as a sample and the ControlFCD program for your convenience.

Important: Download and use these programs at your own risk. They work fine for me on Windows XP, but you may need to modify the VBS for your own use and you will need some basic programming skills for this purpose. They are also likely not to work in later version of Windows, without changes. I can't provide you support about them.

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