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New 6400M Sometime won't start, distorted terrible transmit audio

Jimw6lg Member ✭✭
I received the 6400M from Flex on Saturday. Since that time I have tried to use it without success. Sometimes, when I turn it on, I get the message to wait and nothing happens. i waited 20 minutes. It then says to pull down to restart. When it does start, the transmit audio is distorted with a digital clipping as described by about 20 others. I tried to the stock mic, BM800, Heil, Astatic, Shure SM7B and others. All give the same terrible result. Processing off, Normal, DX and DX+ all result in complaints of terrible audio. With the equalizer on or off, it does not matter. The response is "pinched", "does not sound good", "there's something wrong with that transceiver and send it back. The mics are direct to the back. I've been on the air for almost 60 years and this is by far the worst experience with a transceiver. Also, I did a reset with no change. I have K3 to listen with and the Flex does sound like ****. 73, Jim Heath W6LG


  • KD0RC
    KD0RC Broomfield, COMember, Super Elmer Moderator

    HI Jim, I think that the most common cause is that the mic gain is not set properly. Set the mic gain so that the little peak indicator (circled below) is around -5 dB. At no time should it go into the red. In the screen capture, I had a hard time capturing the screen at exactly the right moment, so my peak is normally just a tad higher. Anything over -10 but less than zero should give a very clean signal.

    If you already have this set properly, it might be RF getting in somewhere.

  • Jimw6lg
    Jimw6lg Member ✭✭
    I had it much less than that with the processor off and on and off using the stock FHM3 mic. It sounds digital with distortion. I am honestly pretty unhappy so far because of all of the bad reports. Thanks Len, 73, Jim Heath W6LG
  • KD0RC
    KD0RC Broomfield, COMember, Super Elmer Moderator

    Ah OK Jim, Do you have the TX equalizer on? If so, try with it off. If you still have bad audio, I would suspect an RFI problem.

    If you are really sure that it is not RF getting in, I would submit a helpdesk ticket.

  • Jimw6lg
    Jimw6lg Member ✭✭

    I tried both on and off with the equalizer. I used the same mics and cables that are used with my Elecraft K3 and K3S. I have one inch wide flat strap to the transceiver from a pipe under the desk that is connected to the frame of the desk. The room has rigid foam with foil. There is also 2 flat copper strips that are 3 inches wide and parallel that lead to the grounding system. Mic cables are very good coiled cords. Two the mic are completely metal housings. The distortion does not sound like RF in the audio. It has a odd digital weirdness. Thanks for your help. 73, Jim

  • Jimw6lg
    Jimw6lg Member ✭✭

    I ordered one with the antenna tuner. The one I received does not have the ATU. Also, the bias voltage in stand bye is just 2.9 volts and not 5 vdc as indicated in the instructions. I have requested an exchange and asked to get what I had ordered; 6400M with ATU. I suspect I got a defective transceiver by mistake that should not have been sent out. It is not my fault and I should not have to pay for return shipping. I sent the request yesterday and I hope to get an answer today. At this point, I am pretty upset with Flex and hope to get it resolved without causing me a lot of grief. I have the beginning of Leukemia, myeloydisplastic syndrome and do not need stress. 73, Jim W6LG

  • Arizona Mike
    Arizona Mike Member, Unconfirmed
    This is my first post here and I am very concerned.

    I have read an extreme number of Flex issues dating back to 2018. It seems that the QC of these radios may be lacking. I am very nervous about ordering a 6400 although I have been having a tough time between the 6400 and 6400M I ordered the 6400M two days ago.

    That little voice keeps telling me to move on and don’t go down the Flex highway.

    So confused.
  • Neil D Friedman N3DF
    Neil D Friedman N3DF Dayton, OHMember ✭✭✭

    4.5 years with my 6600M and not a speck of trouble. I suspect 95+ percent of Flex owners find the same.

  • John KB4DU
    John KB4DU Member ✭✭✭

    Mikie, although no product is perfect, the flex radios have a good track record for reliability. I have had only one issue with my 6400 in 4 years, and it ended up being user error. What is seen here is much like reviewers of cars, hotels, and phones. The ones having issues predominate, with vast majority just keep hamming without a squeak. Flex offers a 30 day return if not satisfied, the service department is very good, and the help desk far exceeds any other manufacturer. The radio is very different in design philosophy from other radios and requires some adjustment mentally. For example, most others have features “baked in”, while the flex uses additional external software to add desired features. The 6400M front panel cannot access most of these, but an external windows pc can be used simultaneously to provide them. There is also iOS, iPadOS, and Mac access.

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


    This is not normal and I have opened a support ticket for you regarding this.

    I know I am biased, but our radios do get glowing audio reports. I was even surprised this morning when I was using SmartSDR for iOS to my remote 6600 that someone on 80M said it was my best audio ever. Go figure. :)

    The support guys will work with you on this to ensure that it isn't something that isn't right on the user configuration side first and then, if it has a hardware issue, they will take care of it for you. Starting with the handmic is a great first step as that actually sounds not bad.

    I never depend on anyone else to tell me how they want me to sound. I used the FDX feature of the radio so I can listen to myself.

    Here is a video describing it: