Welcome to the new FlexRadio Community! Please review the new Community Rules and other important new Community information on the Message Board.
If you are having a problem, please refer to the product documentation or check the Help Center for known solutions.
Need technical support from FlexRadio? It's as simple as Creating a HelpDesk ticket.

Choppy Transmit Audio Flex 6400M

Good Afternoon Everyone,

I am hoping you can help me to figure out why my hams I rag chew with on 80m are hearing an intermittent chopping or popping in my audio when transmitting. The solution so far has been to reboot everything including the 6400M, PC, and SmartSDR. This is a new Flex 6400M purchased at the Dayton Hamfest.

My PC:
Operation System - Windows 10 - 64 bit
Processor - AMD Ryzen 9 3900X 12 Core
Ram: 64 GB

I would appreciate any help

73 de N4KMG
Wes Wingo


  • Alan
    Alan Member ✭✭✭✭

    Where is your microphone plugged into, the Flex radio or the PC?

    If plugged into the PC, popping is most likely related to the PC's configuration.

    If plugged into the Flex radio, popping is most likely caused by third party applications sending subscription requests to the Flex Radio.

    Alan WA9WUD

  • Erik Carling EI4KF
    Erik Carling EI4KF Member ✭✭✭

    Not wishing to be contentious but I have a computer of similar specification to Wes, high end with top CPU and a lot of RAM. I also have a multitude of 3rd party apps working with my 6400M. I do not have the slightest negative artifact on my transmit audio. I would be inclined, if I were Wes, to provide more detail about the microphone type, how it is being used, even an audio recording. If no solution found here, given that this is a new unit just purchased, open a support ticket and supply Flex directly with maximum information and settings details as possible. They will surely help.

  • Mike-VA3MW
    Mike-VA3MW Administrator, FlexRadio Employee, Community Manager, Super Elmer, Moderator admin

    To follow up on what Alan and Erik mentioned, those are great points.

    Often, when there is artifact on the transmitted signal there are many factors that can contribute. This is why more detail provided the better.

    What we see on support calls are related to:

    • over driving the Mic -
    • Network communications loss between the radio and the user
    • WiFi or LAN network
    • LAN Card on PC (NIC cards) driver very old and not updated
    • Cheap switches that have lots of packet loss or are impacted by RFI

    The more detail you can provide, the more we can help you isolate the issue.

    Often, a video of your in transmit should SmartSDR is very valuable to help isolate the issue.

    Tell us more of the story.


  • PunchingPastor
    PunchingPastor Member ✭✭

    @Erik Carling EI4KF and @Mike va3mw

    Thank you very much for the advice. I also put in a ticket with Flex. The choppiness or popping, as my friends who hear it call it, is very intermittent. I made sure I am not overdriving the Rode KT tube condenser microphone and keep it between -5 and -10. Also I made certain the downward expander is not set too high so as to cut off my transmitted audio.

    I am running the following switch for my network:

    I am at a loss as I am turning off any programs that would stress the CPU and GPU. Every 3-4 days the choppiness will reappear in my transmitted audio and the only solution is to reboot the Flex and PC. Thanks for any additional advice.

    73 de N4KMG


  • Mike-VA3MW
    Mike-VA3MW Administrator, FlexRadio Employee, Community Manager, Super Elmer, Moderator admin

    This video might help. It doesn't exactly match your situation, unfortunately, but I put it here for others to see.

    What is your hard drive health like?

  • John WA7UAR
    John WA7UAR Member ✭✭✭

    My take on this thread seems similar to my experience with what I called "network stuttering". I submitted my request to Flex support and got back the following information:

    The analysis of your HelpDesk support incident has concluded that the issue you reported is a known software defect in SSDR v3.3.****

    This issue has been logged as defect number: SMART-8823 & SMART-8824

    The issue is most severe when using two clients and more than three slices combined between them.

    Unfortunately, at this time there are no known workarounds. However, limiting your total slice usage to TWO will help.

    (Tim later wrote:) Please note that this is a high-priority issue for the next release of SmartSDR.

    This issue has limited the number of receiver slices I can effectively have open on my 6700. I am limited to just TWO slices instead of the EIGHT that was available to me before my upgrade to 3.3.32 -- and so when I share my radio with a ham friend in a retirement home using MultiFlex, then he and I are limited to just ONE slice apiece.

    I hope this message post is helpful -- and hopeful -- for folks here.


  • PunchingPastor
    PunchingPastor Member ✭✭

    Thank you @John WA7UAR for the feedback. I only run 1 slice thus far with my Flex 6400M

    73 De N4KMG


  • PunchingPastor
    PunchingPastor Member ✭✭

    Thank you @Mike va3mw I will give the video a watch. It has been very frustrating BUT I absolutely in love with my 6400M, PGXL, and TGXL. Ordered all at Hamvention 2022 and the choppy audio is the only problem I have come across.

    73 de N4KMG


  • John WA7UAR
    John WA7UAR Member ✭✭✭

  • Wolfgang
    Wolfgang Member ✭✭

    @John WA7UAR Hi John, we have exactly the same issue with our remote station and the Flex 6700 in the Swiss Alps. With the SmartSDR version 3.3.32 we have the same Issue. One of us is able to use 2 DAX streams at the time. If I login with SmartLink and would like to have a SSB QSO - no way - thy audio is popping and not usable ! So one of us has always to logout in order that one user is able to use the flex 6700 properly.

    I have a quess:

    I can't find any CPU and memory information about the built-in hardware in a Flex 6700.

    I guess there is not engough CPU power or memory or the new smartsdr software has another software architecture with the latest v3.3.32 version.

    I would be very happy to know the truth of the cause.

    73 de HB9RYZ


  • Mike-VA3MW
    Mike-VA3MW Administrator, FlexRadio Employee, Community Manager, Super Elmer, Moderator admin

    The audio popping is related to network communications, but more work needs to be done to isolate the cause. The audio popping is just the symptom we need to figure out.

    As for CPU information, you want to watch your task manager at the time you have issues. Are any of these graphs at very high levels?

    You generally do not need DAX streams for SSB communications unless you are doing something specials with it. Again, share with use what you are trying to do.

    SmartSDR does not use a lot of computer power, but a simple test is to reduce the display RATE and FPS to the left and see if the problem changes. This will reduce the amount of data being sent out of the radio.

    The hard part is that not all network switches are created equal. We have some sound Gig switches to be absolutely terrible with critical streaming data. I am not sure why, but I would love to know.

    If you really want to test your network performance, there are tools such as jPerf that will give you some great data to review.

    I'm not saying your radio does or does not have an issue. Just that there are a number of players in the network communication game and we have to figure out who isn't holding up their end of the solution.

    I hope that helps a bit.

  • Wolfgang
    Wolfgang Member ✭✭

    Hello Mike

    Thanks for the tips. But we are using the best hardware and have very powerful Windows 11 PCs. The audio popping is also there with the new Mac Min (M1) and with a high-end Windows 11 PC.

    At our remote site we have a 100/100 Mbit/s fiber internet connection and a 1 GB network switch with a Business BinTec RS123 router/firewall in use. So only the best components.

    When I say CPU and memory, I mean the CPU and memory in the Flex 6700.

    Because before v3.3.32 we did not have this effect.

    Our workaround now is to **** DAX and then switch to SSB to get a clean audio signal.

    Bye the way, we reported this issue months ago.

    by the way, are you testing Smartlink with Multiflex in the lab?

    73' Wolfgang

Leave a Comment

Rich Text Editor. To edit a paragraph's style, hit tab to get to the paragraph menu. From there you will be able to pick one style. Nothing defaults to paragraph. An inline formatting menu will show up when you select text. Hit tab to get into that menu. Some elements, such as rich link embeds, images, loading indicators, and error messages may get inserted into the editor. You may navigate to these using the arrow keys inside of the editor and delete them with the delete or backspace key.