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Possible sympton of overheating Flex 6500 using FT8

In the last week, I've begun to have my 6500 refuse to transmit when answering an FT8 station. This happens after I've been on the air for a while and successfully making contacts. The radio will click over into transmit but nothing will be going out as shown on the SSDR display. Trying to figure out what's going on, I hit "tune" and it does show a signal transmitted, but won't transmit if I hit "MOX". This afternoon, I quit the SSDR and WSJT (and JTAlert) software and restarted the programs. The radio then would transmit when I clicked to answer a CQ but the SSDR transmit display looked distorted to my eye, and no one would answer. I'm thinking this shows that something had overheated or been overdriven. After a few minutes of checking to see if my software settings had gone awry (and they all looked good), I tried it again. This time I was able to make contacts again.

Does this look like a hardware failure or am I overdriving the radio somehow? (The DAX TX gain meter looks OK.)

Thanks for any ideas. -- Bill, KA6T

Best Answers

  • billspeedie
    billspeedie Member ✭✭
    Answer ✓

    Thanks for the idea Don. I usually run about 100 watts, but had the idea that the less than 30 seconds tx/rx cycle of FT8 would allow the finals to cool adequately. Maybe not. What software addon is available to report the temps?

  • KD0RC
    KD0RC Member, Super Elmer Moderator
    Answer ✓

    Hi Bill,

    SDRMonitor from K9DUR works great and can be placed on the top edge of SmartSDR where it is easily seen, but does not get in the way.

    K9DUR - SmartSDR Utilities

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

    There is no issue with FlexRadios running FT8, so let's squash that rumor right now please. Even at 100 watts there is not an overheating issue.

    As for other vendors, I can't answer for.

    @billspeedie When it fails, do you have an external watt meter to measure RF power as you don't mention it.

    There are software conditions that can happen where it looks like all the audio is making it to the radio, but there is no RF output. This problem goes away after rebooting the radio and restarting DAX. This is not a hardware issue based on what you are saying in your initial description.

    Also, if the radio was truly overheating then TUNE would fail and you would have warning messages regarding the radio overheating. Are you seeing any?

    If you want to monitor the radio temperatures, you can use FRStack (or NodeRed flows). https://www.mkcmsoftware.com/Flex/Index



  • VE7ATJ_Don
    VE7ATJ_Don Member ✭✭✭

    Hi Bill... what power level have you got the 6500 set for? It could be, depending upon SWR, etc. into the antenna, that at full power the finals are getting overheated and are shutting down to prevent damage. I don't run FT8, but I imagine that the continuous duty cycle might be a bit much at full power over a long period of time.

    Just a thought. There are software addons available which will measure and report the temperature of the finals -- that may be a place to start.

  • WX7Y
    WX7Y Member ✭✭✭

    Perhaps you may want to check the Chassis fan's in the 6500 because it is a little older radio and the fans may be starting to slow down, The fans should also increase in speed the warmer the radio gets and you should be able to really hear them speed up the warmer the radio gets.

    The Chassis Fans are 80MM Fans with the TACH wire and if someone has changed the Fans out with the wrong fan's they may not be speeding up enough OR the CFM is wrong.

    Just a few thoughts

  • Ha Gei
    Ha Gei Member ✭✭✭

    It seems tht it is an inherit problem of FT8 . I see it Killing FTDX10´s , FTDX101´s , TS990 and SSPA´s. The timing design is killing the linear´s . There are many discussions around where even 30% of max power has killed the transistors. Be happy when the Flex refuses to be victim.

  • WX7Y
    WX7Y Member ✭✭✭

    Yea ALL the Radio manufacturers need to really do more design engineering for better cooling for modes even modes that are 50% duty cycle like FT8.

    You really don't want to stop having more modes being invented just because your radio wasn't designed to run them.

    I have been running modes that are high duty cycle like SSTV since the early 80's so have always built my station for Higher then normal duty cycle.

    Even things that you wouldn't think of right away like Baluns, Feedline and Antenna's need to be MUCH MORE then what they rate them for.

    I fried a 7K Watt commercial built Balun just running 1350 Watt's mainly because of poor design on it's poor wire connections inside the Balun.

  • billspeedie
    billspeedie Member ✭✭

    Mike, thanks for your response. No, I haven't seen any warning messages from the Flex software, and it's reassuring to hear that it doesn't seem to be a hardware problem. If or when it happens again, I will look to see the indication of my MFJ-949E in terms of watts out.

    Interestingly, my Malwarebytes program doesn't like the look of the mkcmsoftware site, though I'm sure that's one of those instances where the internet protection software misidentifies a safe site as something bad. As a side note, I get occasional warnings from my Bombast Cable internet provider that someone has tried to hack my Flexradio. Probably not related to this problem, but given the bad stuff that goes on in cyberspace, I can only wonder.

    73, Bill -- KA6T

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

    Hi Bill

    I am not familiar with Malwarebytes, but it is a falsepositive. As for Bombast Cable, what are they monitoring that would cause them to report that?


  • billspeedie
    billspeedie Member ✭✭

    Hi, Mike,

    The Comcast app on my phone reported "An IP reputation security risk [that] happens when a device coming from a high-risk source tries to access a device on your home network." It was titled "Security risk on Flexradi-OC10" and says "We have blocked a known malicious IP from Russian Federation from accessing this device."

    If the cable company did block the incoming attempt, it probably isn't related to my radio not putting out a signal, but this is beyond my knowledge of how that would work.

    -- Bill, KA6T

  • DH2ID
    DH2ID Member ✭✭✭
    edited December 2021

    I've been working F8 for years now (15000+ QSO's) and never had any overheating problem with my Flex-6500. If the signal is not going out, the most likely culprit is WSJT-X, which has scrambled it's ini file. I have made a backup of the ini file and I just play it back. That helps every time.

    Vy 73 and merry xmas, Alex - DH2ID

  • John KB4DU
    John KB4DU Member ✭✭✭✭

    I did some testing on the FT8 duty cycle on flex 6400, monitoring the temp of the finals. I was never able to get finals temp anywhere near critical temperature.

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