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Set AGC To Fast

Hi I been hearing a lot of crackling or what sounds like something arcing and the Flex 6400 is picking it up. Seems to be most noticeable on 40 meters. I was told to get the AGC to "Fast" and this should correct it. Where is the adjustment for the AGC located at ? Is it on the slice control or right side controls ?

Here is a video I made of the arcing sounds the Flex is picking up on my antenna. It does not do this with other radios just on my Flex 6400.

Thank you.

Video link here: https://youtu.be/nIwRNzIKUYk?si=_sK-Q64X0PLMjhx0


  • KD0RC
    KD0RC Member, Super Elmer Moderator

    Hi James, Set the AGC by clicking the speaker icon to open the screen shown below. The AGC speed can then be selected using the drop down box (I keep mine on MED). I don't think that the AGC speed will have much effect on noise, but the AGC Threshold (AGC-T) can have dramatic results (control marked with the arrow, below). Try lowering the AGC-T value so that the noise is noticeably reduced. The higher the noise floor is, the lower the AGC-T should be. There are a couple of really good YouTube videos about setting this control by Mike, VA3MW and Tim, W4TME. The goal is to lower the threshold far enough to stop amplifying the noise, but not so low that you stop amplifying weak signals.

    It is hard to tell from your video, but the noise sounds a bit like lightning. I find that even with the AGC set to MED, lightning crashes recover extremely fast, and have a minimal impact on communications (they are still quite annoying, however...).

  • Ken Wells
    Ken Wells Community Manager admin

    Some of that noise also sounds like it could be generated with the Windows Sound...

    Can you connect powered speakers to your radio's PWR SPKR output and turn PC AUDIO off?

    You will get better performance that way, if you are close enough to the radio for that.

    I use MED or SLOW almost exclusively on SSB because then I don't hear the noise and junk between the syllables of the other station talking. It is much easier on the ears.

    Also, adjust your AGC-T (Threshold) down a bit until on a quiet frequency the noise just starts to drop. This makes for a much quieter session.

  • KG5PTE
    KG5PTE Member ✭✭

    I do not use the PC audio and do use an external speaker. I can also hear the crackling when remote on my Ipad.

  • Erik Carling EI4KF
    Erik Carling EI4KF Member ✭✭✭

    Note as well as the advice above that your network status, especially when the issue is at its worst, is showing yellow bars and no bars illuminated. Network problems are not good for audio performance.

  • KG5PTE
    KG5PTE Member ✭✭
    edited November 6

    I have no idea what yellow bars and no bars is ? Where is this on the slice ? A little more details please.

  • Erik Carling EI4KF
    Erik Carling EI4KF Member ✭✭✭
    edited November 6

    Unbroken audio is more likely with full green bars. This is not necessarily the cause, just pointing out that it it may not be helping.

  • KG5PTE
    KG5PTE Member ✭✭

    Understood thank you. This sounds logical.

  • Scott-ka0jwc
    Scott-ka0jwc Member ✭✭

    Ive been having a similar issue using Ver 2.10.1 SW.

    Also the radio/SW has been quiting on me randomly. Today, while in the middle of a QSO, the SW just quit telling me that it lost connectivity with the radio. Everything was on and working.

    Re=booting everything helps for a while, but the popping audio remains

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

    Odds are that this is a computer network/communications issues. When your network (including the computer) gets network congested, the packet data stream is corrupted. It can then cause a issues in the NIC cards on the computer. SmartSDR gets confused and crashes.

    The things to look at are network cables, network switches and computer speed/performance. Not all network switches are created equal. Some are good and some are, well, just bad.

  • KG5PTE
    KG5PTE Member ✭✭

    Well if it was network communications issue I sure I would hear this on all the bands and not just on 7 MHZ. I do use a n ASUS RT AX82U Router and brand new Cat 6 Ethernet cable to the Flex I never hear this on 28 MHZ and very rarely on 14 MHZ but 7 MHZ all the time.


  • WX7Y
    WX7Y Member ✭✭✭
    edited November 13

    Try powering down the radio (pull 12V) and bring it back up for a test to see if that helps at all.

    my friends 6300 does this once in a while and that's about the only thing that helps.

    I believe that the firmware has a small memory leak and when the radio has been powered on for several days there is no room left.

    Another thing that may cause it is if your running some OLD! versions of 3rd party software like FRSTACK or Node-RED they can beat up the radio with IP Port 4992 requests again this is a OLD problem that was fixed by those software gurus a few years ago now.

    this is JUST my opinion and isn't worth much at all

  • KG5PTE
    KG5PTE Member ✭✭

    Yes I have noticed that leaving the Flex 6400 on 24/7 is not a good idea. It seems that rebooting or shutting down about every 2 or 3 hours is best. You can't leave the milk out of the refrigerator very long to get warm or it goes sour. I have heard this from many users that use Flex Smart SDR version 3. And this is why a lot have stayed with version 2 smart SDR.

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

    Expanding on James' insights, I'd like to share my experience with my 6600 and 6500 radios, which I haven't rebooted in an extended period. Operating exclusively in remote mode, I haven't noticed any significant issues.

    It's important to emphasize that leaving your radio on continuously poses no harm. This is consistent with my approach to computers as well. My Windows PC often runs for months without a restart, while my Linux systems, like my DX Cluster on a PI4, have consistently operated for an impressive 400 days without any adverse effects.

  • Geoff AB6BT
    Geoff AB6BT Member ✭✭✭

    Slightly off topic...but if I leave my 6400 on for an extended period the transmitted CW characters are mangled, improper spacing, missing dits or dahs.

    The only solution I have found is to restart the radio.

    Long-standing problem...

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