XM radio noise feedback

Is there a way to reduce or avoid the high pitched feedback apparantly produced by the power supply from my Whelen strobes? There is also a high pitched feedback without the strobes, but they make it worse. Using a 396 with audio jack. Thanks...

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    I am not knowledgeable with the capabilities of the 396 beyond its function as a GPS. I understand you may be using the XM signal to add weather to the display, and music?

    Is this a new problem, that is, one that has just recently started? If so, what changed?

    Most high pitched whine is sourced at the alternator and is usually filtered by the battery. An alternator whine varies with engine RPM. Since you note that you're experiencing a whine even with the strobes OFF, you have eliminated the strobe power supply as the primary source. But, it could still be a weak battery. If possible, swap in a known good battery and try to repeat the problem.

    In flight, I would try switching OFF various electronics, one-by-one, until you determine what is causing the problem. Or, on the ground, start with the MASTER turned ON, power up the XM components, while isolating them from the 396. Then, power the 396, then your audio panel, or whatever your using to monitor the audio. Do not discount your headset as a source of the problem. I had a Lightspeed headset create such extreme feedback that my COM radio was unusable. A new headset solved the problem. It's pretty much a matter of troubleshooting. Try the easy things first, keeping notes of the effects.

    Occasionally, a "ground loop" can cause this kind of problem. A "ground loop" is caused by having several electronic devices connected to several different grounds. Ground loops can only be avoided by connecting all electronics to one common ground. As we add new "goodies" to our planes, we often use the nearest airframe ground, rather than a common ground. That starts the problems.

    Corrosion is a constant source of problems as our planes age. Ground connections that become corroded also become sources for ground loops.

    So, I don't have a direct answer for you. But, as you research the problem, post your findings and I'm sure more knowledgeable people will be able to help.

    VFRs, without TFRs,
    Dennis-ARR
  • Have a similar issue with a 496, GMA 340 audio panel, & Whelen strobes. The noise is diminished by disconnecting the audio jack from the 496 but it does no go completely away. I don't listen to the XM radio inflight and get traffic & terrain advisories from a 530W. The advice above to selectively disable avionics and note the effects is sound.
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