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connecting an external amp to 6400

I bought a DX-e amp that I used with my IC-7300. I also bought the vendors band decoder so the amp would follow the ic7300. The vendor doesn't make a decoder for Flex. The link for amp https://www.dxworld-e.com/product-page/hf-6m-linear-amplifier-500w and link for the decoder - https://www.dxworld-e.com/product-page/band-decoder-for-icom-1. The amp has a male 8 pin round connector that the vendors decoder connects to the ic7300.

Recently bought a 6400 and would like to be able to have the amp follow my 6400. I have looked at several you tube videos and searched here. So time to breakout the tools and see what I need to home brew. I bought a sainsmart 8 ch board and the Flex usb to serial parallel adapter.

long question but any pointers or assistance would be appreciated.



  • KD0RC
    KD0RC Member, Super Elmer Moderator

    Hi Art, do you know which of the pins control which bands? Do you know if the bands are selected high or low? It looks like certain bands are paired in the amp, so you will likely need to use some diodes (diode OR) to logically OR them together.

    The Flex USB BIT cable will probably do what you want, but you will need to wire the lines to the connector correctly. You will need to be aware of voltages on the pins (Flex expects 3.3 V), what pins control which bands and their polarity.

    Take a look at the SmartSDR documentation, page 125:

    BIT cables provide a means to map the tuned frequency of the radio to a set of individual signals/wires at the end of the cable. These cables are designed to control external devices when the radio is tuned to specific bands or frequency ranges, and for external keying or sequencing that is triggered when the transmitter becomes active. The signal that appears on each bit/pin of a BIT cable is configured by use of the controls in the USB Cables menu: 

  • olson339
    olson339 Member ✭✭

    I sent my question to my amp vendor regarding the interface and pin assignments/voltage requirements.
    His response was

    The band jack on rear panel has 8 pins.
    To enable the band you want must provide +12v on pin.

    Pins are:
    1 160m
    2 80m
    3 40m
    4 30/20m
    5 17/15m
    6 12/10m
    7 6m
    8 GND

    The jack is GX16-8.

    So on the surface it appears I need to build an interface that would step up the voltage from the bit cable to the correct pin on the amp. any thoughts?

  • KD0RC
    KD0RC Member, Super Elmer Moderator

    Hi Art, yep, you will need a transistor to switch 12 V that can be triggered using 3.3 V. It is very important that the circuit never allows anything over 3.3 V to get to the Flex cable.

    The other thing that you need to design is a way to trigger one line on the amp from two lines on the Flex (e.g. 30/20). A diode OR should do the trick.

  • olson339
    olson339 Member ✭✭
    Got advice. Thanks for you help.
  • olson339
    olson339 Member ✭✭
    Meant good. Darn auto correct
  • Mike-VA3MW
    Mike-VA3MW Administrator, FlexRadio Employee, Community Manager, Super Elmer, Moderator admin

    This might help a bit too! :)

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