Sunday, August 17, 2008

Software Defined Radio

The WV DX Association has been asked to prepare the 2008 DX Forum for the 50th Annual WV ARRL Convention (and Roanoke Division Convention) and I have agreed to give a demonstration of the software program, CW Skimmer, at that Forum. In preparing for that, I realized in order to fully display all the power of CW Skimmer I needed to be able to input a broadband portion of the radio spectrum. CW Skimmer works well with just the 3 kHz passband of a regular transceiver but it works SO much better if it can see a larger slice of the band.
This can be done with a very simple, direct conversion type receiver which delivers I-Q audio signals to a computer's sound card. The receiver downconverts a 48 kHz section of RF and then quadrature samples that and produces two signals at audio frequencies which represent that RF but which have a 90° phase difference with each other. The computer then takes those signals and processes them in much the same way a regular radio does.
In searching for a simple way to do this, I came across the SoftRock series of "Software Defined Radios" (SDR for short.) These are sold as kits by Tony Parks, KB9YIG, of Springport, IN. I contacted Tony via email and he agreed to build a 40-M version of the SoftRock Lite version 6.2 receiver for me. THANKS TONY! Below you can see a photo of the completed receiver. It is just 1.5 inches square. (Click on the photos for a larger view.)

Connecting this radio could not be simpler. An antenna is connected to the antenna input, 9 VDC to the black/red wires, and the Stereo Audio Output cable is plugged into the Line (or Microphone) input of the computer. Now all you need is the "software" portion of the "Software Defined Radio." For that I downloaded THREE different programs which were all FREE! Click on the names of the programs to visit their respective web sites:

Rocky by VE3NEA who is also the author of CW Skimmer.
SDRadio by I2PHD.

I was able to use all three of those programs with the SoftRock 40 just fine. All have a different "look and feel" and have different features. You can also use PowerSDR which is the software used with the FLEX radios sold by Flex Radio Systems. They produce a very high-end SDR that you may have read about in a recent QST review.

But, since my purpose in acquiring the SoftRock 40 was to demonstrate CW Skimmer, I needed to download and get that program running. That turned out to be a simple task. HERE is the page that describes CW Skimmer. You can download a 30-day free trial from the "Download" link on the top right of that page.

Below you can see what I was able to copy on the SoftRock 40 using CW Skimmer for about 4 minutes on Saturday night. The list of stations copied by CW Skimmer totals 31 including: 9A2EU, F3NB, GM4FAM, HA9PP, I2AZ, LZ3FN, RA1AR, UT7NW and VE1DT among several others. Not too shabby for just a 1-1/2 inch square circuit board, a laptop computer and an 80-M Inverted-V antenna!!

I will demonstrate several other VERY interesting features of both the SDR radios and CW Skimmer at the 2008 DX Forum at Jackson's Mill on Sunday, August 24th, at 9:30 a.m. Oh, I should mention, as I stated above, the software part is FREE and the SoftRock 40 kit costs a whopping $10. WOOF! That's the best "bang for the buck" I've seen in a LONG time!