Hi Alberto and Guido, > --- In [email protected], Guido <[EMAIL PROTECTED]> wrote: > > > > A while ago there was this interesting idea by Phil Covington where > > only one audio channel is required for implementing a kind of QSD; > > called RMSD. The idea was posted as a SoftRock SuperLite idea where > > only a single switch does all the mixing and image rejection. At the > > time of posting, questions where raised how the image rejection > > would work and the idea was maybe misinterpreted and not fully > > understood. Did anybody solve the puzzle? > > > > 73, Guido > > Guido, I would like to be proved wrong, as that would mean a progress > in the SDR field, but, lacking further explanations or evidences, I am > convinced that it can't work. > But, as said, let's hope that Phil himself would give more > explanations instead of thinking about exploiting commercially that > idea, as he said he was intending to do... the obvious solution is to use an I/Q mixer to generate two signals that are then filtered to a bandwidth well below half the Nyquist frequency of the soundcard. One would then use a switch at Nyquist/2 to alternate between the two signals. The SDR can monitor the phase of a reference signal at Nyquist/2 to use to decide when one or the other channel is sampled. My guess is that one could receive a bandwidth of Nyquist/4 quite easily. If you just want a narrowband SDR with negligible component cost this could be an attractive solution.
73 Leif / SM5BSZ
