Hi KE5FX,
This looks like USB data loss to me. If you looked at the CW output in the time domain and it looked like a pulsed waveform (non-periodic/intermittent), that would be the tell tale sign. Definitely looks like a pulsed waveform in the frequency domain.
We have seen this with the VSG60. Here are some ideas,
– A single USB 3.0 port will usually power the VSG60, except on the most ultraportable devices like the surface pro. You could rule that out with a powered hub, but it’s unlikely the issue.
– The PC is underpowered. I would recommend 2-4core or greater i5/i7 processor. We use libraries that are not optimized for AMD processors, so if you are running an AMD, that might be the culprit.
– Enable high performance power plan. See attached picture for instructions. This has helped a lot of customers in the past.
– The power saving CPU mode was one way to combat this on newer machines. Newer (8th gen or newer) Intel processors have a low power state (the C3 state) that interferes with USB transfers. It can create large enough latencies transitioning into/out of that state to cause data loss on our device. We have limited buffering on the device itself to absorb these kind of latencies in the USB3 hardware itself. The USB chip manufacturers suggestion is to spin off a busy thread to keep the CPU busy and not go into this low power state. We do that when Power Saving CPU mode is enabled. We have seen another alternative work, on some PCs you can disable C-states from the BIOS. This will definitely cause your PC to draw more power, but might resolve this issue.
Threads with more information.
https://community.cypress.com/thread/36763?start=0&tstart=0
https://community.cypress.com/message/194853#194853
– The sample rate used for CW output in the GUI is 50MS/s which could be lowered to reduce USB requirements. The range of rates that the device natively uses are 25-50MHz. I can reduce the sample rate for CW signals on the next release, I think this would help you on this PC. The rate used for multi-tone is selected based on the multi-tone configuration itself, and it appears there are lower rates that work just fine on this PC. Look out for the next release, I’ll get that in there for you to try.
What OS are you using?
Regards,
Andrew
