I fired up my 12 today for a flight and when I powered up the avionics, I noticed a whine in the radio audio. It appears to be alternator noise as it accelerates with rpm increase. I also hear the strobes flashing. I know we have filters on the fuel pump and a/p servos, but don't recall any in the charging circuit. Anyone else experience this? Mr. Gores, any advice?
Thanks in advance.
Hello Dave,
We can probably help you better via email, but regardless, it will be important to gain a better understand of the meaning of "whine in the radio audio".
As you know, your GTR 200 provides intercom audio, COM radio audio (receive and sidetone), optional alert audio via the AUX 1 and/or AUX 2 mono audio inputs and optionally music audio via the stereo music input.
It will be important to understand which audio path(s) are picking up the noise.
For example, "radio audio" seems to imply that you are hearing alternator whine when receiving on the COM radio, but since this isn't mentioned specifically, perhaps you are referring to intercom, alert, or music audio.
Even if you can hear the alternator whine in the intercom audio, we wouldn't know if it is really just present in the intercom audio without removing the alert AUX 1/2 audio and music audio contributions.
To shut down the AUX 1/2 audio input path (probably only AUX 1 used on your RV-12), go into configuration mode and set the AUX 1 and AUX 2 volumes to 0%. Write down the old setting so you can restore it after making this test. If the alternator whine is now gone, we know that it is being coupled in on one of the AUX audio inputs.
Shutting down the music input is simple. Either turn the music input off (most of us have one of the two softkeys set to music on/off) or set the music volume to 0%.
As part of your noise input isolation testing, you might also unplug each of the headsets one at a time and see if that makes a difference.
Once you can provide some additional information on which audio stream the alternator whine is present, we might be able to suggest some mitigation.
Thanks,
Steve