FT8 distortion

Sergey KN7K

I paid attention today on my signal during TX and I see it has intermittent distortion on waterfall, some TX clean, some TX have a little distortion, some more.
Restarted DX, it did not help.
Is that normal?
Flex 6600 ver 3.1.12.

Thanks
Sergey, KN7K

Bill -VA3WTB

It is normal. The water fall and panadapter shows things that are not transmitted. Unless your over driving. Make sure you not over driving.

bahillen

This is probably being transmitted. It is caused by a Windows interrupt affecting the RX audio. The interrupt is generally caused by the processor CPU not being able to handle a process in a timely way. Caused by having to many things running. Chrome can be troublesome, Spots on a busy band, out of date drivers, monitors not on a separate graphic card especially with 1080 or 4K, not enough RAM, a slow network connection. Look up LatencyMon in the Flex blog to get a app to monitor interrupts and identify driver or processes with issues. Tim is the expert. The Task Manager can Be very helpful. Try running with not much else running and compare the pops. On FT8 it has been my experience that one or two pops in the 13 second period did not harm my contact. I now keep all my drivers up to date regularly. If you run LatencyMon, it is just a tool to identify if it is getting interrupted and the cause. When you run it it may indicate 100 or 200 useconds then jump to 400 then 1,000. Kind of cascades. Write down the process or driver name and search internet for what it is. It it runs long enough it seems you will eventually get an issue but that is not a problem. Look up Tim’s article. Keeping windows open that are not needed wastes CPU. Turn off Spots. Use a Gb Ethernet switch directly between radio and computer. Dumped Norton virus protection and use Defender. I run I7-7700, 16Gb RAM, NVDIA , graphics card, SSD. It took me 6 weeks to discover what I had to work on like pealing an onion. Now I run 4 FT8 instances with 3 monitors and seldom see a problem but it occasionally does pop. I took the same actions on my old Dell 5520 and use it without problems but less instances and screens. Point being you don’t necessarily have to buy a new computer. After you make progress you can add things back in. 73 Bill W9JJB

Doug Hall

W9JJB, your experience matches mine. A "pop" now and then doesn't seem to hurt anything. Your remediation suggestions are good ones.
73,
Doug K4DSP

Sergey KN7K

Thank you Bill,
All good suggestions.

I have pretty powerful PC

Windows 10 with up to date SW

PC – Intel i7-7700@4.2GHz

RAM DDR3 – 64GB

Video card – NVDIA GeForce GTX1080

HDD – Intel SDD1TB

Network Nighthawk 8500

Network switch TP-Link TL-SG108

Yes, I run everything from one PC - many Chrome windows open, Spotify, SSDR, Stack3, Slice Master, PGXL utility, AG, sometime Photo related SW.
Even I play movie and with everything open my PC is comfortable at CPU around 20-25%, Memory ab out 15-18G B out of 64GB, GPU at 22-25%.

I am pretty sure what I see on waterfall is getting out. I have to think what other possible drivers could be out of date and if this is am issue.

Sergey, KN7K

Bill -VA3WTB

As a rule of thumb it is not a good idea to look at the Tx on your screen to determine of your signal is good. The reason is, the TX is being mixed with receiver noise and the returning signal coming back into the radio. These along with your TX signal are a all shown on the panadapter. I will mostly look messy. But what you see is not usually transmitted.

To watch you TX signal, use the FDX feature. Set up a seconds slice on the same freq as slice B . Set slice B as Transverter receive. Transmit on slice A. You will then see just what your TX looks like. It should be clean,,unless as I mentioned before something is going on,,like over driving.

Bill -VA3WTB

What you are seeing has nothing to do with your computer. The computer does no processing for the radio. Everything is in the radio. The only component that does any work is the video card in the computer because it has to draw what the radio sends.
It may be possible to over tax a computer because of all the programs running for your shack, and the computer could slow down. but what is seen on the panandapter is all in the radio it self.

KD0RC

Ken Wells, NM9P has a fantastic video in how to monitor your outgoing signal.  His emphasis is on good audio equalization, but this is still valuable for any mode:
https://www.youtube.com/watch?v=CzT1qDKKySk
73,
Len, KD0RC

Doug Hall

That simply isn't true, Bill. The FT8 signal is generated by WSJT-X and sent to the radio via DAX. As you know, WSJT-X and DAX are both PC applications which can be impacted by the very things W9JJB mentions. If realtime is broken for whatever reason then there will be a dropout in the audio fed to the radio. This dropout causes a discontinuity which results in a noticeable (and real) disruption in the RF output. It has nothing to do with the Flex, which is just reproducing the signal fed to it.

KC2QMA_John

Bill VA3WTB: "As a rule of thumb it is not a good idea to look at the Tx on your screen to determine of your signal is good."

So basically turning on the “Show TX In Waterfall” is useless and serves no real function other than it’s looks pretty cool and will impress your friends in the shack.
Yeah that seems right.

Bill -VA3WTB

Yes, If you do a search on this subject you will run across the thread were Flex explained in better detail than I did. All I can do is inform.

Bill -VA3WTB

Doug, you make a good point, if the software used for digital work messes up the TX signal than yes the software and computer can be at fault. And it's not a Flex problem.

KY6LA_Howard

Actually its quite useful to show that you are transmitting OK
It definitely will show dropouts when they occur
More importantly i will show splatter when things like you overdrive DAX or DAX has an error.