Radio interference playing CD/Aux Sony 6 CD HU in Focus ST

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Believe this stereo is fitted to a lot of Fords. Ever since having the car I've noticed whereever I play a CD I get interference from the radio that I can hear it in the back ground.

Any idea if it will be the arial connection lose on the back of the HU, or will this be a HU issue?

Thank you

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Disconnecting the battery seems to have helped. Defo not as bad