It’s hard to imagine
that it has anything to due with the exhaust since the spatial relationship
between the exhaust and antenna does not change with aircraft
pitch.
You might try
adjusting the squelch. I had a similar problem with noise when I went
fast, or sometimes on climbout. Finally realized the sound level in the cabin
was going higher and overcoming the squelch setting so I was hearing cabin noise
on the sidetone from the mic. A small tweak on the squelch knob made it go
away.
Al
G
-----Original
Message-----
From: Rotary
motors in aircraft [mailto:flyrotary@lancaironline.net] On Behalf Of Bobby J. Hughes
Sent: Tuesday, October 06, 2009 2:54
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