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PR781 Heil Mic Issue

Joseph Rodick
Joseph Rodick Member
edited March 2019 in FLEX-6000 Signature Series
I have a flex 6300. I am using a PR781 Heil Mic, with the Bal Cable. I am getting reports of motor boating audio, almost like computer generated tone. When I use the Flex Mic supplied with the 6300 the motor boating is gone. Any Clues?


  • Neal_K3NC
    Neal_K3NC Member ✭✭
    edited July 2014
    Sounds like RF is coming through the balanced cable, I would put a toroid on it.
  • Joseph Rodick
    Joseph Rodick Member
    edited March 2019
    just added four toroid coils on the balanced cable, till getting the motor boating sound using the PR781
  • Neal_K3NC
    Neal_K3NC Member ✭✭
    edited July 2014
    Still sounds like you are getting rf in the balanced line (not sure how but if it doesn't happen when coming through the front panel but does through the balanced line, thats all I know it can be!)

  • Joseph Rodick
    Joseph Rodick Member
    edited March 2019

    Just ordered another cable from flex.  Thank you for your assistance.



  • np2g
    np2g Member
    edited November 2015
    6.1.2 Supported Microphone Types
    The FLEX-6000 front microphone connector can support either a dynamic or an electret
    microphone. This is an unbalanced high impedance input. The electret bias voltage is not
    enabled by default, and must be enabled by SmartSDR. The DB 15 in the back does not provide a balanced input It provides a Plus audio input and a Frame ground .
  • Burch - K4QXX
    Burch - K4QXX Member ✭✭
    edited May 2016
    I had this issue the other day with my 6300.  Was using a heil headset with the adapter for the 8 pin mic connection in front of the radio.  Several stations said I had the "motor boating" on my signal.  I turned on the monitor and sure enough, I could hear it.  I unplugged the headset and plugged it back in and it's not done it since.
  • Jon_KF2E
    Jon_KF2E Member ✭✭
    edited July 2018
    While adding a toroid to your mic cable may be the answer, people need to understand that all toroids are not created equal. Mix 31 toroids work best for HF frequencies. Mix 43 will work above 10mhz. Unless you are sure of the composition of the toroids you are using, they may not help at all. Almost never are toroids bought at hamfests identified.


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