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Flex 6600M keying Henry 3K Premier amplifier.

Steve KD2OM
Steve KD2OM Member ✭✭

Simple question, how do I key the Henry amplifier safely? The amplifier keys by a ground closure. It has +26 volts on the key line.


Steve KD2OM


  • Jim K4JAF
    Jim K4JAF Member ✭✭

    Good luck on this one.. As I remember from some years ago, the Henry used a large open pole relay with no suppressor diode across the coil thus one heavy back surge when keying.. My best to your radio keying circuit.. Jim K4JAF

  • K5XH
    K5XH Member ✭✭

    Hi Steve,

    I have keyed a Henry 2K and a SB200 amp with my 5000 and 6600. I built a little circuit in a small box to go between the Flex and the amp. It was just a junkbox 12V relay and a couple other parts. The relay contacts connect to the amp. I believe I used a couple of transistors and a couple resistors. Probably an easier way but I used what I had.

    A friend keys his older amp with one of these: https://www.dxengineering.com/parts/ame-arb-704

    Hope this helps!

    73, Mark K5XH

  • Steve KD2OM
    Steve KD2OM Member ✭✭

    Thanks Mark,

    I found a solution that I already had but forgot about. I have a Denkovi USB relay board that the 6600M recognizes. I just configured one of the relays to key the amplifier.

    I looked into the ARB-704, that probably would have been the next step.


    Steve KD2OM

  • HalM
    HalM Member
    Harbach Electronics sells a small Keying Interface circuit board that protects sensitive HF radios from
    high-voltage Keying energy in older Heathkit amplifiers.

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