Flexradio 6700 Popping Crackling sounds while operating remote

David Decoons, wo2x

You can use the Maestro over VPN. You'll need a device on Maestro's network to set up the VPN tunnel.

My home router is set up with VPN server enabled and my BERL travel router is set up with VPN client. I can connect the Maesstro to the travel router along with iPad, laptop, and anything else I need.

73 Dave wo2x

Paul Christy

Maestro works fine over Smartlink. The problem is SSDR audio has intolerable crackling / stuttering on Windows PC over Smartlink. Sounds like it would definitely be worth trying your VPN system if I can figure out how to set it up... Thanks!

Paul Christy

Mike-VA3MW

A few things to keep in mind.

When using SmartSDR, Maestro, iOS or MacOS over SmartLink the audio streams are compressed to reduce bandwidth. We doubt that it is even noticeable to the user and is no less latent that normal operation.

If you move to using a VPN such as SoftEther that can handle the required Layer 2 UDP packet broadcasts, there is no compression at all since SmartSDR believes you are on a local Lan and there is no need to compress it.

The problem is SSDR audio has intolerable crackling / stuttering on Windows PC over Smartlink.

I doubt in your case moving to a VPN would resolve the packet losses you are hearing. And, given the Maestro is fine that tells me the network between the radio and the Maestro is good and if the PC is using the same network then we have to accept the fact that the network is good for the PC.

The clicks are 100% related to data loss which means we need to focus on the communications layers(s). Not all switches and WiFi access points are perfect. Not by a long shot.

If I had this on my desk, I would not assume the PC is perfect. It sounds like a NIC card issue with the card flapping possibly on negotiating speeds.

Here is what I would do not knowing anything about the computer you are using.

• Update all the hardware drivers on the PC. This includes the NIC cards and WiFi adapter cards. Don't forget the BIOS update.
• Do not use WiFi for any testing, at least to start and only test on a cabled solution
• Change any cables that your data runs through. Yes, there is such thing as a bad cable that sort of works
• Try a different network switch. Stay away from $20 special 1Ghz switches. We have had many users share experiences.
• Lastly, run some DPC latency tests and make sure the PC is not overloaded. It is good to read up on DPC Latency. We have a tendency to assume it is perfect and not busy. Your computer might be fine, but measure it anyway so you have some solid data to work with.

Which got me thinking, what is your display resolution and what sort of display card are you using? If you are overworking the Display and you don't have a separate display card, the main computer takes the load.

YMMV

Paul Christy

Hi Mike,

Thanks for your thorough assesment of my situation. I guess I'll save the VPN idea for last and look into each of the hardware issues you mentioned. Looking forward to seeing what the DPC tests show. Also, I'm due for new laptop and desktop computers so maybe that'll help.

Still very frustrating that the DAX stream remains pristine and PC Audio is crackly. That demonstrates to me that there is a software issue in the PC Audio stream. Maybe next contest I'll try using the DAX stream. I haven't looked into the ramifications of doing that but maybe that's the way to go until there is a fix.

Thanks,
Paul
N0GN

Iu4jnr

Paul,

Mike pointed out the high DPC latency which would cause cracks.

There is an actions that can help to mitigate the high DPC latency. You can just try to disable USB selective suspend.

Look for advanced power settings; Change advanced power settings then expand USB settings; Expand "USB selective suspend setting" and disable it.

Max Iu4jnr

Paul Christy

Thanks Max. Tried it. No difference. In my case this is OBVIOUSLY an SSDR software problem. If I listen to the DAX stream on my PC, it is Pristine. When I listen on PC Audio it is very crackly. It's all on the same PC. It has to be software.

I'm not sure of the downsides of wasting the DAX stream in my case. Maybe none. Going to try it this weekend in WPX contest. In the meantime, I sure wish they'd fix it.

Mark SQ2GXO

Hi Paul,

I'm having the same problem with following setup:
Flex 6400 connecting remotely via ZeroTier VPN (no Smartlink).
Audio crackling when using SmartSDR on Windows PC and Windows laptop.
When listening to DAX stream on same PC - there is no crackling.
I also hope it can be fixed by Flex software developers.

Mark SQ2GXO

Paul Christy

I hope you solved your problem. If so, please let me know how you did it. I think if you ran a Maestro over the same connections, it would work fine. Problem is in Windows settings or SmartSDR. Not much incentive for them to fix that... There is a workaround. Listen to audio on DAX channel through Audacity. Quite the Kludge. Haven't been doing it for long but it's working pretty well for me so far. Guessing I'll find some downsides to this in the future.

Paul

N0GN

Mark SQ2GXO

@"Paul Christy" I've solved problem by buying Mac Mini and MacOS version of SmartSDR.
The issue is very likely related to audio buffer size. MacOS version of SmartSDR allows selecting output audio buffer size.

@Mike-VA3MW The issue is related to bad internet connection with high jitter. Due to this, not all audio packets arrive on time (they came in eventually but too late to fit into small buffer). It can be simply fixed by using larger audio output buffer size inside SmartSdr. I work as software developer, though not on Windows, still can't believe it is so hard to fix?

73,
Marek SQ2GXO

Paul Christy

TL;DR - It is basically the network but a Major Mystery remains. Cross posting to the other active threads. Sorry.

I'm glad to see so much interest in this ongoing problem. The thing that has always baffled me and still baffles me, and the question to which I, and SQ2GXO have never gotten a satisfactory answer, is why are there no crackles when listening to the DAX stream or on a Maestro over the exact same networks? SQ2GXO went so far as to purchase a Mac and it worked on the same network. That's dedication but really shouldn't be necessary.

Incidentally, VA3MW noticed I cut off my exchange in the CQ WW DX SSB Friday night. That was not due to the network problem. It was because in N1MM I program F3 and F4 to turn MOX on and off in lieu of PTT/footswitch. Sometimes, I'm a little quick to hit the F4...

Anyways, I've tried many different things, none of which seemed to immediately result in significant improvement. However, when I fired it up from my offsite location (see my QRZ page), in the last hours of the contest last night, the crackling was gone! It remains so this morning. So I thought I would summarize all of the changes that occurred in the last week, and notes from earlier years, leading up to this moment.

Switched ISPs from Verizon Business 5G + WeBoost to Windstream DSL. We're in a rural location. I have both.

Hardwired Ethernet at offsite location instead of WiFi.

New network switch at the station TP-Link TL-SG1024DE.

New network patch cables at the station DbillionDa Cat8.

Windows 11 Advanced System Settings offsite location: Visual effects all turned off except Smooth edges of screen fonts, and Adjust for best performance of: Background services (instead of Programs).

I've always used fairly low bandwidth SSDR display settings: AVG 90%, FPS 15, RATE 60.

Direct wired connection from computer to radio has always worked fine.

In the past, messing with numerous NIC settings did not result in improvement.

I've had up to 4 monitors hooked up to the new 2025 Carbon X1 laptop, but the problem exists even when using the laptop undocked.

Previously changed MTU to 1500 with some improvement but back to 1467 now.

SSDR Network Diagnostics have generally been Excellent to Good but this morning they are impeccable with 0.00% dropped packets (31/1,205,400).

Thanks everyone for your input.

Paul

N0GN

Keywords ****, cracking, crackle, crackling, stuttering, pop, popping