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Have opportunity to purchase a 2 year old 6400M w/ant tuner.

Appreciate the assist on questions I should be asking of the seller about the rig. This would be my first opportunity to own a Flex but want to make sure it's the right one.

Thank you and 73's,

Best Answers

  • Johan SE3X
    Johan SE3X Member ✭✭✭
    Answer ✓

    Ask for Software version installed? It follows radio and if it has V1 or 2 and you would like all current features of V3, you will face an upgrade cost of 200 USD. I would ask if fan modification been done (you will find more about that if searching this community). Otherwise not much to ask for in my mind. Hardware wise they are the same delivered today as two years ago.

    Good luck!

  • Ted  VE3TRQ
    Ted VE3TRQ Member ✭✭✭
    Answer ✓

    The 6400 came with v2 software. The real question there is has it been upgraded to the version that does not have SD card corruption problems.

    The 6400 has only one fan, and if it is working now, should have no issues. It was the 6300 and 6500 that had some fan issues.

  • Johan SE3X
    Johan SE3X Member ✭✭✭
    edited January 2022 Answer ✓

    Not sure what you mean Ted? If you buy a 6400 today, does it come with V2? Is that what you are saying, or are you aware of this specific 6400 the question is about? There are versions of both V2 and 3 that should have the fix for SD card corruption.

    No fan issues with the 6400? https://community.flexradio.com/discussion/7925017/new-series-radio-fan-failures-my-two-6400s-both-died

    I rest my case and will not comment further.

  • KD0RC
    KD0RC Member, Super Elmer Moderator
    Answer ✓

    Hi Richard, The real question is what do you want to do with the radio?

    If you are looking for SO2R operation, or want to listen on two different antennas simultaneously, you will want a 6600 or 6700.

    If you are interested in full duplex satellite work, the 6600 with its two Spectral Capture Units (SCU) has two transverter ports, making it a great satellite radio.

    Otherwise, the 6400 is a great rig, and even with one SCU, it has the ability to listen on two frequencies simultaneously and can even operate in Full Duplex by using the RX or Xvtr port for the second receiver.

    The other advantage of a 6600 is the 7th order bandpass filters on the contest bands. If you plan on running multiple transmitters in close proximity, this could make or break your contest operation.

    The 6400 has 3rd order bandpass filters. I have run my 6400 at Field Day within 100 yards or so of another 6400 and we did not get in each other's way at all on harmonically related bands. We were even able to operate on the same band, as long as one was on CW and the other on SSB (we could tell the other was there, but still operate).

    Bottom line is basically whether you need two antennas simultaneously and/or 50 dB of bandpass filtering.

    Best of luck with your decision!


  • In addition, the 6600M has a balanced audio input and an RXB antenna socket while the 6400M does not.

  • Ted  VE3TRQ
    Ted VE3TRQ Member ✭✭✭


    Fan issues with the 6400 have rarely been reported, although I’m sure they do happen - all mechanical devices fail from time to time. It is the used 6300/6500 Flex radios about which you really need to ask fan questions. And 6400 fans are easily replaced (although you do need to have the correct one - I bought a spare about the same time i bought the 6600M).

    The 6400/6600 radios were delivered with v2 software, of the vintage that suffered from SD card corruption. It is very useful to know if the SD card replacement has been done in conjunction with an upgrade to the version that does not suffer corruption. I’m sure there are many 6400 radios out there that have older v2 or v3 software that need to be upgraded to the latest “safe” software. I did not write a book in response to a simple question, mostly because it was late at night, and I was using a tablet.

  • Further, the 6600M will support 4 panadapters on a computer while the 6400 will support 2 (both will support 2 on the radio’s front screen). A 6600M panadapter has a maximum range of 14 MHz while the 6400 maximum range is 7 MHz. The minimum ranges are 1.5 KHz for the 6600M and 6 KHz for the 6400. Sampling rates are twice as high in the 6600M and the spurious and image rejection rate is 20 db greater.

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