Here is an article I wrote for my club's newsletter:
Dan Dreams!
By Dan W1DAN
OK OK, I tend to get caught up in the excitement of technology. This is a blessing and a curse, but I feel life is more fun when you are playing with some new piece of hardware or software. This last month I did both with Dream.
All this started when a fellow ham (JT, WA1TDH) got interested in a PC software application called HamDream. HamDream is a software program that allows two hams to chat via HF, but using digital audio instead of the usual SSB. The result is no fading, noise or distortion. This program is the grandchild of Digital Radio Mondiale (DRM).
DRM has been used by a few shortwave broadcasters for a couple of years now. DRM sends digital audio over the big shortwave transmitters such as Radio Canada’s Sackville site and is received by a special radio, or a modified radio, a converter and some PC software. The end result is that you can listen to Radio Canada, the Voice of Russia, Deuche Welle, or Radio France with no interference, noise, fading or distortion. DRM also can pass stereo audio, images and text information as well.
Well, Some friends of JT started looking into HamDream, but JT really wanted to listen to DRM. Until recently, DRM software was sold for about $100.00 from the DRM web site and equipment manufacturers like Ten Tec. JT kept asking people he knew in the industry whether they could give him a copy of the commercial software. Not receiving any results, and asked me to see what I could do.
I looked around the web a lot and finally found a web site (
http://drm.sourceforge.net) that two graduate students at a German university had. They created software that ran on Linux that decoded DRM. Later a compiled a version of this code for Windows, called Dream was created. I had struck gold!
Once I told JT of this find, Harry KK4QK and John K9FB started building converters (from a FAR Circuits PC board) to allow their standard shortwave radio to feed their sound card so the Dream software could decode the digital stream. John was the first to get the whole lash-up to work. He discovered that the converter drifted and designed a crystal oscillator to eliminate the drift.
I got exited, and gathered up an old box, a perf board and most of the parts to build a converter (my junk box really paid off as I only had to buy one connector). I was on 75 meters a couple of weeks ago talking to Bill KE1GF who played with Dream for Linux about a year ago and had limited success. He offered to send me a crystal oscillator and a couple other IC’s, which I promptly installed.
I downloaded the software, modified my Yaesu FRG 7700 receiver to get an IF signal out of it and plugged in the converter. Once I ran the software and tuned in a station, I heard music from Germany!
We have been comparing notes via e-mail and making further small improvements to our reception. This all has been great fun!
Dan