Garmin SL-40/DRE intercom motorboating

[jimbower]

Whenever I transmit on the radio, I get a motorboating sound in the headsets. This sound does NOT seem to be transmitted (I can't hear it on my handheld), but it is quite obvious in the intercom. Everything is connected per the radio/intercom wiring diagrams, but I'm willing to double-check anything.

I have tried numerous ferrite cores on the antenna wire as well as the intercom audio cables (all shielded). It doesn't seem to help.

I am totally open to any and all troubleshooting ideas. Thanks.

Jim Bower
RV-6A Extremely slow build
St. Louis, MO

 

[PCHunt]

What type of headset? ANR?

 

[lrfrey]

Jim I don't have that problem, but had motorboating in the headset when I turned my Dynon on..... Turned out to be a low battery voltage. Don't ask me why that did that. Just a thought.

Larry

 

[jimbower]

Guys,

I apologize for not getting back to you sooner, and thanks for your help. I keep forgetting to check replies to my posts. I am using a Lightspeed ANR headset, but the motorboating occurs whether the ANR is turned on or off. Larry, you nailed it. I turned off my Dynon D-100 and lo and behold, the motorboating stopped! That seems strange because the battery shows above 12 volts, but maybe keying the mic makes it drop (duh!). I wonder if I can use a better source of battery power (jump it from my car?) to compensate, since the little Odyssey battery doesn't look strong enough to run a transistor radio.