--- In [email protected], "drmail377" <[EMAIL PROTECTED]> wrote: > > Hi Lyle, > > I was looking at this. I think the files are also in Files > Si570 > > LPT1. This is Guido's (PE1NNZ) parallel interface. > > However, I would think a better parallel port interface would employ > opto-isolators. Opto-isolators will prevent a potential source of > ground loops.
Unless you already have isolation between the computer and the SoftRock, in the form of isolation transformers on both audio lines, I'm not sure that the ground lead in the parallel port interface contributes much to the ground-loop noise. The real problem comes when the SoftRock circuitry is connected to ground through another path separate from the computer, such as the power supply or antenna. I use an isolated power supply, and the BPF circuits in the v8.3 SoftRock provide isolation from the antenna ground. I have to admit that there is a fairly significant "blip" at the LO frequency in my setup. Fortunately, when using PowerSDR in SDR-1000 mode, the LO is always 11 kHz away from the signal I'm listening to, so it's not a problem other than a distraction in the spectrum display. Lyle, K0LR
