flyrotary@lancaironline.net Mailing List Archive

Joe, while i was hunting down the noises of my system with osciloscope, I discovered that one of my rudder cables was grounded, and the other was not. The one that was not grounded was radiating radio noise. The moment i grounded it it went flat line on the scope. I also grounded all my control cable torque tubes, since some were, and some were not grounded.

I know that the injector wires are transmitting some electromagnetic field constantly, since my vertical compass was dancing like mad. I had to find a different place for it. It is a "black art" for people like us, but you'll stumble eventualy on the cause. It took me a month with the help of electronics engineers, people on the list and oscilloscope.

Buly

On Apr 9, 2006, at 1:02 AM, Joe Hull wrote:

Today I spent most of the day with my EAA flight advisor – much of it was up in his Long-EZ doing drills for my first flight – which I was hoping to be this next week. However, after that I spent a couple of hours in the hanger puzzling over the radio static that only appears when the engine is running AND the mic is keyed (note – no / little noise on incoming broadcasts whether the engine is running or not).

It was windy and rainy this afternoon and I wasn’t able to get the plane out of the hanger for an engine run so I thought I’d double check grounds and shielding etc. At some point I had the bright or not so bright idea to use my handheld ICOM to see if there was any radiated signal from the coils or anything else when the engine was not running that might intensify when the engine is running. A very interesting phenomena soon appeared related directly to the EM-2. When the EM-2 is powered on anything attached to grounded metal (remember I have a plastic airplane and thus well defined ground paths) radiates a static noise on the handheld. For example within about 18” of the engine I’ll get static; or if I go halfway down the wing and sweep it over the wing I will get static when it passes over the part that contains the rudder cable. If I pull the fuse on the EM-2 I get no static anywhere – not even when I key the mic. I unplugged P1 and P2 plugs (sensor inputs) from the EM-2 and still had static – only get static when there is power to the EM-2.
HOWEVER, again, I wasn’t able to run the engine so I don’t know if the static is gone with the engine running and the EM-2 is disconnected.

Joe Hull
Cozy Mk-IV #991 (Done Building! In Phase1 Flight Test - 0 hrs flown)
Redmond (Seattle), Washington