Well, I'm still keen as mustard to have a go at SDR, but have been struggling to get one of the Softrocks – due to availability. Although recently, the "SoftRock RX Ensemble II Receiver Kit" was up for sale but sold out in the same day. (UPDATE: Just as I was writing this I went and checked again just in case, and the Softrock Lite II was up for sale again. It's ordered and now I'm hanging out for it to arrive!!)
So while looking around at other things (WSPRnet actually) I came across mention of the ZetaSDR. I therefore did a search and came across the even simpler TinySDR by LY1GP on the same page – and first at that. It's a very simple direct conversion receiver consisting of nothing more than three parts:
1) Simple LC band pass filter;
2) Mixer; and
No AF amplifier stage, it just feeds the output direct to the sound card MIC input and leaves it to do the amplification etc. Oh, and the VFO is coupled into the mixer via a phase transformer thereby providing two different phases – one at 0 degrees and one at 90 degrees – and thereby making the output that of (I believe) an IQ SDR receiver – like the Softrock (albeit, not as 'advanced').
So this all looks very simple and something I'm tempted to try. But I'm not equipped antenna wise for 80m, and also don't have an oscilloscope for testing etc. However, I figure if I just change the band pass filter at receive and a couple of other points (need to look closer at the schematic) I think I might be able to make it for 40m – which I am equipped for. Plus, I've been considering getting a oscilloscope but haven't had a big need just yet – but now I might….
Anyway, I'll give it some thought and see where I end up. it could be a great project to further solidify some of my study for my license upgrade… (As could the Softrock when it arrives – I guess that could be a few weeks though.)