When i put a usb plug adaptor in to my cigarette lighter and i have my sat nav or my phone chager wire plug in it interferes with the frequency of the radio
My car has 171000 miles.
My car has a manual transmission.
Hi There, I believe you have what is called conducted or radiated interference. From what you describe, it sounds like this is conducted interference. If it changes with RPM change, this suggests it may be noise from the alternator or the rectifiers that turn its output into DC (direct current) which interferes with your USB.
You may have to make some compromises to fix it. I would experiment with other chargers. The USB charger should not be a high current device. MP3 players usually have modest current requirements. Designs tend to vary, and if you can find one that has the parts you need in it, it’s easier than explaining how to add them to your circuit to eliminate the noise.
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