The radio is receiving a weak signal and the tuner is struggling accordingly. You have shown that the tuner is OK by using a giant aerial to capture a stronger signal - my guess - and it's only a guess - is that there's a problem with the aerial cable that goes between the aerial and the radio itself. I suspect that the shield braid is no longer connected at one end or the other.
When you applied the copper pipe you too were forming part of the aerial circuit - I doubt you will find a long aerial that will easily attach - I doubt that the radio has an internal fault - but you never know.
Amazon will sell you a car aerial for £5.35 post free but it will need to have a hole cut in the bodywork to fit it - RMA305
Good Luck...
November 2016
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