Radio interference

[Braincrank]

I just bought a double USB charger that plugs into the cigarette lighter but when I use it I have interference when listening to the radio ? Not a big problem for me because I listen to cd/mp3 but the missus is not happy about it.
Any ideas what might be the problem?

 

[Tebs]

I have a similar problem on my w204 only with the dab radio. DAB Signal cuts out with a phone connected or my pogo alert charging. In fact with anything charging. Ive tried various usb chargers including Belkin and griffin but no joy.

 

[Stratman]

USB is 5 volts, your car produces (nominally) 12volts. The circuitry to do the conversion operates at a high frequency and is highly likely to be the culprit.

 

[Tebs]

USB is 5 volts, your car produces (nominally) 12volts. The circuitry to do the conversion operates at a high frequency and is highly likely to be the culprit.

You`re probably right but I think it goes further and there`s some issue with MB components having some sensitivity to this circuitry as Ive had no problems with the same chargers in a mini and focus.