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Flex 6400 15m Tx failures

NR4A Member
I am a new Flex owner and am having an issue on just 15m CW. It is a 6400 NOT "M"

I have only owned this radio about a month but noticed during transmitting on 15 meter CW at 100w that after a while the RF output drops to zero mid sentence. If I pause for a few seconds power will return to full 100w output. It almost sounds like a heating problem.

BUT: After my restored transmission is turned over any click of my mouse on the waterfall will cause the radio to start the shutdown process and disconnect from the computer. It will then proceed to reboot itself.

It does not do this on any other band. I am connected to my router via the ethernet ports and now running Version 3.4.21 after upgrading this week. I can not say I had tried 15m prior to the upgrade.

I want to say Common Mode issue (RF in shack) may be the culprit but would think 10 or 12m would be causing problems as well. I have tried a dummy load on 15 and have been unable to duplicate the Output failure - but on the antenna it is randomly occurs.

I am open to where to begin looking.



  • KD0RC
    KD0RC Member, Super Elmer Moderator

    I would submit a help desk ticket. Flex support staff are really good at diagnosing problems like this.

  • NR4A
    NR4A Member
    Thank you Len - I just submitted one.

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