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Flex 6400 Built in auto tuner

Hi I am going to be using an Alpha Delta 10m to 160 m Inverted V wire antenna the instructions say the antenna requires a wide range tuner on 40 m down to 160 m . Will the built in auto tuner work on this antenna or do I need a better external tuner ?

Thank you.

Best Answers

  • VE7ATJ_Don
    VE7ATJ_Don Member ✭✭✭
    Answer ✓

    Hi James... the Flex auto tuner is good to about 3 to 1, from my experience. If you have availability of one, maybe check the SWR of your AD Inverted V on the bands you wish to operate and that should tell you if you need an external tuner.

    However, lots of other factors -- type of reactance, grounding, etc. -- can affect whether the ATU will handle the antenna. So, just because it shows < 3 to 1 on all bands on the SWR meter, there's no absolute guarantee the ATU will find a 'match' :-)

  • Randy KN4YBA
    Randy KN4YBA Member ✭✭
    Answer ✓


    To add this thread, for my 6400 I use the MFJ MFJ-939. With it

    only connected to the antenna port of the 6400, you must select tune on the SDR

    for it to actually tune. I did up to a few days ago, had the turner setting on

    my desk, but recently relocated to just below my remote antenna switch. I did

    run a 4 conductor from the turner to my ham shack, 2 conductors for the 12v dc

    to power the turner, and the other two conductors provides me the capability to

    fine tune the antennas. The fine tune conductors are wired directly to the tune

    button of the turner.

    Since moving the turner close to the antenna has made a significant

    difference in better and quicker tuning of all HF bands to include 6m.




  • VE7ATJ_Don
    VE7ATJ_Don Member ✭✭✭
    Answer ✓

    Hi James... re: 75 and 160m... it really depends on your antenna. For instance I have simply a 43ft vertical with a 9::1 un-un at the base and my Flex 6700 ATU handles it rather easily on all bands, including 160 and 75m.

    If you (or an elmer) had an antenna analyzer to look at what your inverted V is presenting at your desired frequencies, that would give you a pretty good answer.


  • KG5PTE
    KG5PTE Member ✭✭

    Do MFJ External tuners work with Flex ?

  • Geoff AB6BT
    Geoff AB6BT Member ✭✭✭

    Why not?

  • WX7Y
    WX7Y Member ✭✭✭

    About any Antenna tuner will work with the Flex like the LDG and MFJ's but there is no way for the MFJ Antenna tuner to key the radio in tune mode like many antenna Tuners do with different radios like say a Yaesu, Kenwood or Icom using a interface cable with a few exceptions, the Tuner must be used in Full AUTO tune mode and should have memory's and a frequency counter to PRESET the tuner a little.

    The MFJ989 has a Frequency counter and memories but takes a brief tune cycle for the tuner to read the frequency.

    The 4O3A/ FLEX Tuner Genius, AT-Auto and with 3rd party software the HF-Auto will follow the radio like a tuner should.

    All Auto Tuners should BYPASS the AMP's PTT when it is busy tuning but ONLY the Tuner Genius, AT-Auto, MFJ989 and the VERY early HF-Auto's have this feature which for me is a MUST.

    This is JUST my 2 cents

  • KG5PTE
    KG5PTE Member ✭✭

    Yes my MFJ 993B Auto tuner has a cable connected to my Icom 7300 and it tunes the radio. But yes I did not think that there is a cable to connect a Flex 6400 to a MFJ auto tuner. So if I use it I will have to do this manually.


  • KG5PTE
    KG5PTE Member ✭✭

    From what I hear from three other that use the A.D. antenna is that 75 meters and 160 meters are the ones that require a wide range tuner. I will be operating mostly around 14.290 MHz on 20 meters and 7.210 MHz on 40 meters. And around 28.400 28.410 on 10 meters.

    Thank you.

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