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CW QSK - Flex 6500

Paul Christensen, W9AC
Paul Christensen, W9AC Member ✭✭
edited June 2020 in SmartSDR for Windows
QSK performance is impressive, especially at this early stage of roadmap development. What's interesting is that it's possible to hear between keyed elements at high QRQ speeds, but due to DSP, a slight latency of audio follows. This may seem like a contradiction, but it's not. QSK is blazing fast and the side-tone keeps up with actual keying. It's only the Rx audio that is very slightly delayed but what's important is that audio between keyed elements is clearly audible. I find only one problematic artifact: At exactly 19 WPM and lower when using the internal keyer (Iambic B), a loud pop is heard when the Rx recovers. At exactly 20 WPM and higher, the artifact is gone. I rarely send at less than 20WPM so it's not a concerning issue but it should be validated by others. The keyed RF envelope is symmetrical, and certainly appears to be a rapidly rising/decaying raised cosine curve. Measured rise/decay is about 4 ms. I see no evidence of ALC power spikes. Overall, QSK performance is excellent. Paul, W9AC

Comments

  • Tim - W4TME
    Tim - W4TME Administrator, FlexRadio Employee admin
    edited March 2017
    Paul, Since your praise topic also had a problem report, I am converting your post to a problem so others can comment.
  • Ken - NM9P
    Ken - NM9P Member ✭✭✭
    edited June 2020
    I just ran some tests. I can confirm that my 6500 begins to have a 'pop' upon unkeying when the CW speed is below 20 WPM. The pop causes a good bit of ringing when using narrower filters on CW. However, if I add a slight bit of delay, (12 and above), the pop and ringing goes away. As reported above, there is no 'pop' at all at speeds of 20 WPM and higher, even with the delay all the way to '0'. (But I can't reliably send faster than 25 anyway and am more comfortable at 18 WPM right now until I get some rust shaken off of the CW fingers and ears!) My tests were run on 6 meters on a very quiet band with the preamp set to maximum gain (20 dB.) and with preamp at 0 gain. The timing was the same. In any case, I am not comfortable with full QSK on a noisy (or extremely busy) band because all the extra noise scrambles my brain when I try to send. So I usually set my delay to listen between characters or words, but not between 'dits.' But it is nice to know that it can do it if I want to! When the delay is adjusted to eliminate the slight 'pop' this 6500 it is as smooth as silk!

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