Sirius Radio- Significant Background Noise (Hiss, Humm, Etc.)

Hey Truckers!

I use the aux-in jack to the 2012 Freightliner Cascadia's stock radio for my Sirius XM receiver. I KNOW that the background noise is coming from the DC plug-in power source because I get the same problem when my iPhone is used to play music the same way. However, if the iPhone is NOT plugged into the power source (running on battery), then the sound is completely clear and perfect with no background noise at all.

I've read other posts regarding this problem with CB radios. Specifically, what exactly IS an "in-line noise suppressor"... how does it work, is it easy to install, where does it go and, most importantly, DO THEY WORK for you? Do they affect the quality of the signal from the Sirius receiver to the radio? How much should I expect to pay, and is one brand any better than another? Any specific "specifications" I should be looking for?

As always... any help is appreciated and welcomed!

 

Good idea... of course, I'm already WEARING the tin-foil HAT!! I'll wear it then snap a pic for my profile shot, right?

 

The operative phrase in your reply is "competent shop"... I am a Company driver, and I think this particular problem would be about at the bottom of their reasons to troubleshoot an electrical system.

Since you seem to know about diodes, alternators, etc... tell me if you think this idea might work. I have a 1500w inverter... so, would converting that A/C current BACK to D/C current for the Sirius receiver likely resolve the "noise" problem? Whaddaya think?

PS Regarding noise when truck shut off, I'm not certain because the DC source is a switched circuit... but I'll try using one that is constant on.