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FLEX 6400 With Amplifier


I'm stuck again. And smartsdr is no help. I want the radio to key up an external amplifier. All of the TX1 TX2 TX3 TX4 cannot be programmed to be usable. Smart SDR doesn't address the 6400. The radio settings TX tab does not show Enable or Disable. The 6400 does have band settings and many options that can be checked or unchecked. Nothing seems to change the TX1 to always key up the amplifier. The profile for my radio TX is default.

Any thoughts? There is a PTT output on pin 11 of the accessory jack. I'm going down rabbit holes again


Best Answer

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

    Hi Fred

    In case you are not aware, there is a sequencer in your radio and you can configure it with SmartSDR as well. You can set it up to handle up to 3 devices and also totally delay the RF out by as long as you like.



  • sdrwow
    sdrwow Member ✭✭


    Thanks for looking. Apparently there was a error in the "polarity" of my PTT system and the Flex radio.

    I reversed the leads from my PTT system and everything is lovely. The Flex 6400 now keys up my system to transmit whether I am using an amplifier or not. I use a sequencer to gently go to TX and come back to RX so not to cause RF damage to any listening antenna pre-amps or my SDR play box. With my Flex radio I really have no use for SDRplay anymore.

    The rabbit holes are gone.

    Fred KC4MOP

  • sdrwow
    sdrwow Member ✭✭

    OK Mike. That's good news abt a sequencer built-in to the Flex. One of those products where almost everything was thought of for Ham radio ops.


  • N5DUP
    N5DUP Member ✭✭
    Fred, what did you mean by reverse polarity in your PTT system? I am trying to key my SPE Expert amp from the TX1 on my 6500 and it’s not working. I am using a Heil trigger switch plugged into the PTT rca jack which does key the radio but I am seeing no state change on TX1 therefore the amp is not being energized (keyed). I have also used the MOX button in SmartSDR, same thing, no state change on TX1.

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