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Thread: readings change while transmitting

  1. #1

    readings change while transmitting

    When I press push to talk, the wind read out, true airspeed and outside air temp become either totally wrong or removbed from view, things return to normal when push to talk is not pressed. I run RG400 coax and haver a common ground for everything. Any suggestions?????

    Gary

  2. #2
    Gary, I had some problems with my wing-tip foil antenna (Bob Archer) disturbing my AFS 2500 when transmitting. I ended up replacing it with another belly antenna.

    Kent

  3. #3
    Gary, check to ensure your EFIS's have a chassis ground to your aircraft and electrical grounding bus. Also ensure the center conductor and shield of the antenna coax are not shorted. It is an interference issue that can be difficult to diagnose.
    ---
    Trevor Conroy
    Technical Support
    Advanced Flight Systems
    Support@Advanced-Flight-Systems.com

  4. #4
    I have the same issue in my RV-8. Have two Comant belly antennas, and the coax has been verified good. The EFIS' are grounded to the airframe as shown in the installation manual. I am out of ideas on how to fix this. Everything else with the AFS installation works properly.
    Jim Shannon
    RV-8 N52VV
    Charlottesville, VA

  5. #5
    I have a chassis ground and good coax, any other ideas? Could the RF from the antenna be causing a "queertron" to act up?

  6. #6
    Quote Originally Posted by garymail View Post
    I have a chassis ground and good coax, any other ideas? Could the RF from the antenna be causing a "queertron" to act up?
    Gary
    These Gremlins can be fun to chase. Make sure none of your coax is ran in or near any of the wire bundles leading to the EFIS. Usually a couple of inches seperation makes a difference.
    do you have 2 radios? does it happen with both ?
    When i finished my Glastar the garmin 300xl was ok but the SL30 was terrible. most of my problem was a defective antenna and i got rid of the rest by unbundling the cable.
    Rex

  7. #7

    erratic readings while transmitting

    I will try disconnecting the black wire to the OAT and see if that works.

    Gary

  8. #8
    I disconnected the black wire on the OAT probe, everything works normally now! Thanks Rob!

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