It’s possible that the slightly different air pressure on
the belly skin, causing metal flexing is affecting the antenna ground plane.
You may need a stiffener plate.
Check the connection of your antenna ground to airframe ground.
Jeff
From: Rotary motors in
aircraft [mailto:flyrotary@lancaironline.net] On Behalf Of Bobby J.
Hughes
Sent: Tuesday, October 06, 2009 6:54 PM
To: Rotary motors in aircraft
Subject: [FlyRotary] Mystery Radio Noise
Got
the plane back together late Sunday just in time for a few laps around the
airport. Oil temps showed major improvements with the larger inlets.
Climbing at 100 mph to 3000 ft, 7200 rpm on take off, reduced to 6500 rpm
at 500 ft agl.
Maintained
6500 rpm at 37" MP for several circuits. Oil temps went to 220F but
started to come down when I leveled off. Water stay at 190F or below. OAT was
88F . My new "test" ducts do not seal as well as the first
set so hopefully I still have room for improvement.
While
level at 3000 ft \ ground speed showing 145 knots I pitched the nose
down and heard a startling noise in my headset. Almost like wires
shorting. Leveled off and noise stopped. Pitched up no change. Pitch down the
noise returned. I decided it could not be wiring and repeated this several
times. It also happened at slower speeds but I don't remember at what speed it
stopped. It doesn't happen on the ground at full power run up. My guess is my
new exhaust is somehow affecting the comm antenna when in a nose down attitude.
The exhaust ends about 1 ft in front and 1 ft to the side of the antenna. Any
ideas?
RV-10
SC Renesis