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Robert McGwier
This is not what we do on the Softrock40. The 11 kHz IF is used in the SDR-1000 in order to do exactly what Frank says and that is avoid 1/F, DC, junk, noise, etc. at 0. We are attempting to maximize the performance.
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On the softrock40, we have one oscillator on the board and it is not steerable. It provides a 48 kHz (theoretically) wide signal. We want to be able to tune ANYWHERE in that band. So we in fact live with the little hump of nasty at 0 frequency and tune the software oscillator from -24 to 24 kHz around the center frequency. We get single sideband demodulation by using a complex tap weight based bandpass filter using a very clever mathematical trick which allows us to do huge, fantastic filters with little more computation than much smaller (and poorer filters) done by the normal convolution. In the newer Windows release which should be out some time next week (depending no Eric's work schedule), PowerSDR will carry SR40 support in the base Windows code, and you can select SDR-1000, Softrock 40, and DEMO (no hardware required) mode from the setup panel after install or the installation wizard during install. Bob N4HY Frank Brickle wrote: --- In softrock40@..., Ramakrishnan Muthukrishnan --
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