Please correct me if I am wrong, but it appears to me that QSK on a SDR encounters a wall at the receive latency interval, which sets a minimum bound for recovery of reception.
After the completion of transmitting a code element, the receiver is going to be receiving the tail of that element for the duration of the receive latency period. After that, the AGC has to recover. Even in split or with a second receiver what will be heard between elements happened the latency interval earlier in time. Current SDR latencies are running in the range of 100ms or more. This latency will have to be reduced by at least a factor of 10 before there can be a 10ms recovery in QSK. The low level of latency required for true QSK is achieved in box- based SDR units like TenTec and FT-2000. Why is it not being achieved in computer-based SDR's like the Flex 5k? My two cents... 73 Ed W2RF On 24 Apr 2008 at 16:58, Dave Blaschke wrote: > The best performance I can obtain for QSK is at the following settings: > GENERAL-AUDIO-Buffer: Size 512, Sample Rate: 48000 > GENERAL-OPTIONS: Process Priority: High > DSP: TX Buffer Size: 512, RX Buffer Size: 512 > Delay (ms): 10 (minimum setting) > > At these settings I see around 10% CPU utilization on the PowerSDR screen. > > With these settings, I am almost, but not quite there. Here is my > complaint. When returning from T to R there is an audible "pop" that > tends to mask reception during Dits and Dahs. I am wondering if > Receive recovery is occurring quickly enough. Elimination of the > "pop" on transition from T to R would go a long way in smoothing out > QSK, in my opinion. > > My method of comparing QSK capability between my SDR-5000 and my > FT1000D is to select the frequency on a constant carrier signal, and > then key at 20 wpm to see how well I am able to hear the carrier > between Dits and Dahs. > > > Dave, W5UN > > > _______________________________________________ > 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://kb.flex-radio.com/ Homepage: > http://www.flex-radio.com/ > _______________________________________________ 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://kb.flex-radio.com/ Homepage: http://www.flex-radio.com/
