CTUN artifact

[W2PA]

I like to operate in CTUN mode. That way the display stays constant while I tune around. I've noticed for a while that I can hear artifacts on some CW signals as you tune across them - not all of them, just the stronger ones. I filed it away as something to investigate - annoying but not severe.

But this weekend in the 10m contest I noticed it happening very dramatically since the band was populated mostly by very weak signals. When a strong one appeared the effect was pronounced.

So I tested it out using a signal generated by another rig in my station - an unmodulated carrier. When you tune around in CTUN mode, the signal broadens and produces a zipping or ripping sound in the receiver over a large tuning range from the signal's frequency. You can see it quite obviously on the display. But it's not a display artifact - the effect can clearly be heard in the receive audio and it drowns out smaller signals.

But when CTUN is off the effect goes away. You still see a smudging effect on the display but that's a display artifact and there is no effect heard in the receiver.

I captured a video of the effect here:
https://drive.google.com/open?id=163SiR ... d146s4DmmJ

It shows the following sequence:
1) Tuning around with no big signal present, CTUN on
2) The big signal appears. Tuning around causes pronounced artifact
3) Turn off CTUN
4) Tuning around does not produce the artifact

Any comments or suggestions? This is seemingly a Thetis issue since it depends on the CTUN state.

[W1JA]

Hi Chris,

I notice this artifact also. Your video demonstrates it well.

Further, I recall noticing this issue way back in November 2016 when I got my 200D and started with PowerSDR mRX. So it's been around a long time.

73, John

[w-u-2-o]

That does not happen here, but I am using an 8000.

What hardware are you using, Chris? And which firmware?

73,

Scott

[W2PA]

Using the 8000, as always, with most up to date FW and Thetis version. This artifact existed for a long time going back to PSDR.

[W2PA]

Here's another interesting clue: The effect is most pronounced when tuning with the MIDI wheel, or dragging the VFO in the panadapter display. It's less noticeable when tuning with the mouse wheel but is still there.

The last time I looked at the CTUN code was a year or two ago so I'm a bit fuzzy on its operation. But I do recall that the VFO changes are handled differently in the two modes. Will have to investigate.

[W2PA]

Issue in the source found and fixed. I'm sending the mod to Richie for incorporation in his code base.

[w-u-2-o]

Sweet!