"amdx" wrote in message
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You may have the clue in your response, "excess was coiled up"
A coil of wire makes an inductor. An inductor is an impedance to high
frequencies.

Would that apply so much to a two-core cable, where at any instant, a
current is flowing one way in one conductor (eg on the way to the appliance)
and the opposite way (on the return) in the other? Would the fact that there
are two conductors tend to reinforce or cancel the effect?

If you have a cable that is too long and don't want to cut it to shorten it,
what is the best way of arranging it so as to avoid/minimise inductance? Is
it better to arrange it in a zig-zag rather than loops?