Hello Brian, > My opinion is that with digital processing it is impossible to eliminate the > delay completely, so if sidetone is preferred it needs to be generated at > the key. It is not impossible at all. One just has to avoid errors. The PowerSDR software runs fine with a Delta44 soundcard and a Softrock receiver with a delay from antenna to loudspeaker of 13 ms with the smallest buffers: http://sm5bsz.com/lir/rxdel/3-26sdr/sdr.htm For good filters you might want 1024 DSP buffer size but that does not mean a long delay. ou should expect 38 ms. I do not know how the TX side is managed in PowerSDR, but in Linrad, my own SDR package, the delay from keydown to full power out is 11 ms: http://sm5bsz.com/linuxdsp/tx/cw/qsk.htm That was in July 2008. Then the delay from antenna to loudspeaker was 53 ms because at that time Linrad could not use ASIO drivers. Today the delay from keydown to loudspeaker output is below 50 ms with good filters and ones own tx rather than a side-tone in the earphones. One can actually hear the echo if there is aurora or a meteor reflection when operating 144 MHz.
SDR is not yet a mature technology. With time it will be evident that your assumption is wrong. SDRs actually have the potential to provide better QSK performance than oldfashioned analog receivers because crystal filters are IIR filters while SDRs use FIR filters. 763 Leif / SM5BSZ _______________________________________________ FlexRadio Systems Mailing List FlexRadio@flex-radio.biz http://mail.flex-radio.biz/mailman/listinfo/flexradio_flex-radio.biz Archives: http://www.mail-archive.com/flexradio%40flex-radio.biz/ Knowledge Base: http://kc.flexradio.com/ Homepage: http://www.flexradio.com/
