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Hi Guys
I wonder if you guys have come across this fault or can help with my search for the culprit.
Having made some alterations to our Dynon Skyview EFIS we went to fly only to have a problem and so aborted the flight.
Previously the engine has been rock solid with none of the new symptoms.
I have an Electronics/Communication systems background.
The problem/symptoms:
1. During taxiing we noticed that every time we keyed the mic of the Garmin GTR225 we experienced significant mixture variations and stumbling of the Engine (Renesis 4 Port - EC2)
2. We then sought to clearly establish the symptoms and discovered that along with the very repeatable interference to the Engine/EC2, the Skyview EFIS was also effected by tx. The vertical speed would go +250ft/min then -100ft/min on keying the mic.
The changes we had made:
1. Changed the Pitch Autopilot Servo to a heavier duty unit (no wiring change)
2. Installed the Dynon Auto Pilot & Knob Panels - this meant a new connection to the the Skyview bus and shifting the trim control (inputs from sticks, Power and output to Electric Trim motor) from a relay deck to the Dynon AP Panel (Build in trim controller).
My thoughts are two fold:
1. RF getting into somewhere it shouldn’t. No changes have been made to the antenna or feed. However, I may have shifted some cables in close proximity to the antenna coax. I had just washed and left wet the Glasair's (fibreglass) vertical fin which has the 1/4 wave dipole antenna inside of it.
2. Earthing issues. There were no changes to the Earth system.
Path forward:
1. Replace antenna feed with dummy load to isolate RF while still drawing current from the GTR225. (Where to borrow a dummy load around here?)
2. Check wiring to see if it is apparent that some have shifted in relationship to the antenna coax.
3. Check Earth buss for good connections.
I do recall hearing someone with a similar fault on an EC2/3 years ago.
Would really appreciate your feedback. I have little experience with RF interference and its rectification(no pun intended). Sincerely
Steve Izett
Perth Western Australia - Glasair Super IIRG - Renesis 4 Port EC2 EM3 RD1C
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