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Raspy sidetone on 6400M

I am relatively new to the Flex community and am still learning the radio. I saw an answer to this question from 2018 and the response from Flex was that an update was in the works that would likely eliminate the problem. My 6400 is running v 3.2.39. Using the CW mode, I have a raspy sound on the sidetone when I key with either a paddle or straight key. It almost sounds like 60Hz but I've had no reports of A/C in my signal. What suggestions does the community have? Thanks!


  • KD0RC
    KD0RC Member, Super Elmer Moderator
    edited June 2022

    Hi Emmett, depending on the powered speakers that you are using, you may be experiencing a ground loop. Try a pair of headphones in the headphone jack with the speakers unplugged. If that sounds good, then it is likely a GL.

    A ground loop isolator can be bought from Amazon for around $10 USD and should clear it right up.

    Amazon.com: Ground Loop Noise Isolator for Car Audio/Home Stereo System with 3.5mm Audio Cable : Electronics

    Another possibility is RF getting into the speakers and/or radio. Try with breakin turned off. If you still have the problem, then it is probably a ground loop. If that clears it up, then you will want to put some ferrites on the cabling to the radio. The ground loop isolator can sometimes help with RFI as well.

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