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DAX TX often "plops" using digital modes

rickd Member ✭✭
edited October 2021 in DAX
Im fairly new to the flex, so i might be doing something wrong here.
During TX with JTDX I can see sometimes that the signal uses the full bandwidth (see screenshot).
Im still being received ok, but when I listen to my signal i can hear the "plop" in the audio signal.
Im using a Mac book pro, i9/32gb ram. Smart SDR for Mac version 1.9.14 (124).
For audio im using loopback, but i have tried soundflower as well.

What I have tried:
- play around with the audio output from JTDX
- play around with the gain in DAX
- used a different mac book (but essentially same software setup)

When I monitor the audio using loopback I dont hear the "plops", so i dont think its generated by JTDX, rather by the DAX software.

Any suggesting is appreciated ..
Happy to post in the mac smart sdr section of the forum if that would be a better place.


Best Answer

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

    There are a few things about this.

    While in TX with JTDX, you will see the SmartSDR screen pop. This is not related to API commands being sent to the radio which you can hear in headphones.

    The big question is if this 'pop' is actually bing transmitted (it isn't). To be sure, listen to your transmitted signal on a 2nd slice and see if you can hear it.

    This confirms what you are reporting.



  • Mark_WS7M
    Mark_WS7M Member ✭✭✭

    Hi Rick,

    I also run a lot with SmartSDR Mac these days and also run FT8. While I have not spent much time to monitor as you have, I will try to see if I see/hear something similar.

    I do watch my TX on the pan and I do see this very wide "plop" right after TX starts but usually after that it seems to be very consistent.

    However when I get a chance I will try monitoring the signal with my 7610 or another slice.

  • David Decoons, wo2x
    David Decoons, wo2x Member, Super Elmer Moderator

    The “pop” can be triggered by programs sending TCP commands to the radio while it is transmitting. Not saying this is the only cause.

    What programs are running when this happens?

    Try rebooting the MAC (not radio) and run just SmartSDR for MAC and test. If it still happens with just that program running then turn the radio off, remove DC, wait 1 minute and turn the radio back on and test.

    If this is an M series radio, follow the proper shut down and power up.

    Dave wo2x


  • Patrick
    Patrick Member ✭✭✭

    This happens on windows also, popping in the audio when the radio is doing processor controlled functions like starting a profile that has more then one slice in any combination. In my case with my 6700 I will have profiles to set up an HF slice and a VHF slice. When staring the profile I will get a pop and I will get random pop noise even with the squelch set. In fact to minimize the pops I have to set the squelch rather high. This minimizes the pops but does not eliminate. These squelch pops are not from real externally received signals. As to what causes these pops, it I think originates with the processors in the radio causing the pops in the audio. Probably killing the digital audio words causing audible distortion we hear as pops. It is not limited to any particular model or type of computer or OS. But it is internal to the signals process in the radio. Just my opinion…..

  • rickd
    rickd Member ✭✭
    edited October 2021

    @David Decoons, wo2x Hi Dave, thanks for the reply.

    All I have running communicating to the radio is SmartSDR for Mac. With CAT and DAX enabled. For CAT i only have slice A enabled with type FlexRadio CAT.

    I just borrowed my wife's windows laptop, running smartsdr 3.2.39. I still see a 'plop' once in a while, but not like on the mac. On the mac its exceptional not to see a ''plop', while on windows its exceptional to see a pop.

    Should i look at the DAX imlementation on the Mac? I dont believe its my Mac itself. My old macbook is a clean Big Sur install with the same problem. I just dont know how to report that as a problem? Support ticket?

    @Patrick it sounds like you are talking about hearing "plops" during receive? Or did i misunderstood you?

    @Mark_WS7M it looks like you have the same. I almost always see that wide (looks to be as wide as the used bandwidth) "plop" at the start and then in some tx session its clean. But in others I can get multiple more, like in the screenshot.. Im currious if you see the same as me.

    Btw, my CPU usage is low. not more than 20% for system and user together.

  • Alan
    Alan Member ✭✭✭✭

    Patrick said, "......like starting a profile that has more than one slice in any combination....".

    I have been doing some "Wire Sharking" of the Flex API. I notice that when the Flex Sever is commanded to change slices, a "sub slice all" command is also sent. I suppose this is a method to get the Flex Server to provide an updated Slice status.

    Dave, WO2X, and I have found the when subscription commands are sent to the Flex server, there is a very short interruption of TX and RX audio, i.e. "pop".

    Most times, this "subscription command" caused pop may not be noticeable, as it occurs when a slice is added or removed, and you are not listening for it.

    Just a theory, for now.

    Alan. WA9WUD

  • David Decoons, wo2x
    David Decoons, wo2x Member, Super Elmer Moderator

    @rickd you can open a Help Desk ticket with Flex. The author of SmartSDR for MAC can check if anything in his software or recent update to MAC OS may be causing the problem.

    I am not a MAC user but with the Flex API I have noticed as Alan said that TCP commands sent to the radio during TX can cause popping.

    If you are using the built in logbook or FT8 in SmartSDR for MAC then maybe the programs are sending status requests to the radio at regular intervals? Just guessing.

    See if there is a pattern to the pops using MAC (such as every 10 seconds, for example). If there is a pattern then it may help pinpoint the cause.

    Dave wo2x

  • rickd
    rickd Member ✭✭

    @Alan @David Decoons, wo2x thank you both for the replies ...

    Let me do a wireshark as well to see if i can see something happening at the time of the "plop". That would indeed explain it. It might be simply because the mac smartsdr version is behaving differently...

    Sadly there is no pattern in the pops ... sometimes it just happens when i go crazy with my mouse pointer, sometimes not . Thats the frustrating part ...

    Anyway, thanks for your help so far. Let me investigate more and open a ticket wit hthe additional information

    Rick DU6/PE1NSQ

  • rickd
    rickd Member ✭✭

    @Mike-VA3MW Sorry Mike, i didnt see your reply. It moved up to the top ...

    Yes I can hear the plop on the signal when I monitor with an external device. One doesnt seem to affect my received signal by much, but in some cycles i have many of those plops in my tx signal.

    I have opened a support ticket in the mean time, since a wireshark didnt provide (me at least) with more information ...



  • David Decoons, wo2x
    David Decoons, wo2x Member, Super Elmer Moderator

    Rick, keep us posted on the outcome. Wondering if other MAC users experience this.


    Dave wo2x

  • rickd
    rickd Member ✭✭

    Will do Dave ... thanks for your help so far!

  • rickd
    rickd Member ✭✭

    Just an update on this.

    Ive been talking with support on this and it comes down that they are able to replicate the problem, but since Mac users are using 3rd party virtual audio cables (I tried them all, with the same results) it is not supported by Flex and Marcus.

    I've argued about that, but the answer was to use the internal tools in Mac smartSDR, which i dont want to for several reasons. Any follow-up on the ticket have gone unanswered ...

    I guess thats customer support ...

    I will update my mac tonight to Monterey. Hopefully that will fix things, but i dont exect it ...

    If anyone else has a solution i would greatly appreaciate it ...

  • rickd
    rickd Member ✭✭

    Ok another update...

    I just found xDAX (xDAX 2.0.dmg) and im using that instead of the built-in DAX of smartSDR.

    The outgoing audio signal (monitored on air and within smartSDR) has been clean as a whistle. To my that proved that DAX within smartSDR is the problem.

    I will make one more attempt to get Flex to look at this, but i dont have high hopes ...



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