Inteference from phone with Amplified Speaker Mount

[LostAtSea]

Having finally got around to installing my car kit, I now find that the amplified speaker mount I bought for my PDA is picking up the phone's signal and giving me a lovely crackling buzzing noise.

I've moved the phone as far away as possible, but still get the inteference. It seems to be directly "activating" the speaker, as even when I remove all the leads from the mount and leave it turned off, it still buzzes away.

Short of cladding it in lead, any ideas on how to reduce the interference?

TIA

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