Paul and others, Indeed you can generate Digital Modes as I&Q components from a sound card stereo output. I've been involved in a few successful trials.
I believe there's I&Q PSK31 software about, I have an experimental I&Q version of DominoEX for use on LF, and there's a very nice I&Q output in DRM Dream, for transmitting 10kHz bandwidth DRM. It's the latter that I'm most familiar with. Grant ZL1WTT has built a couple of simple I&Q exciters (I have one) for 80m, using a ~14MHz crystal oscillator and Johnson Ring counter to generate the quadrature clocks. While it's difficult to generate much power with the linearity necessary for DRM, I have received Grant's 5W signal with enough S/N to recover very nice clean audio. I would guess that 10kHz wide DRM on 80m is not something you could do in the USA! The problems we have proceeding further with I&Q for digital modes can be summed up as three factors: 1. Insufficient software with I&Q transmit capability. I'd like to see it offered in all the popular software. 2. Complete lack of I&Q digital mode reception software. I&Q reception is at present limited to the Software Radio audio business. For digital modes we need the software to be both the receiver and the digital mode decoder - or use two sound cards. So far there's no I&Q software for digital mode reception (please prove me wrong!) Digital mode receiving software at present works only with audio or with 12kHz IF (such as DRM, although SDRadio will handle 12kHz IF). 3. You have to build your own gear. This will make the popularity of the approach much more limited. If we had the software, the idea would be more popular. By the way, the I&Q transceiver would be much more popular if there was also audio I&Q for voice input from a microphone - so you could also use your transceiver for SSB. 73, Murray ZL1BPU
