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Hello dietnews. In addition to the remedies suggested by The Crow, here are my experiences which might explain what is happening.
What frequency are you on? Find out the frequency of the interfering station. If it is a nearby frequency, chances are your transmitting antenna, which is tuned to your precise frequency (the antenna Q), may be acting as a receiving antenna and picking up the other station and re-modulating it in your carrier.
The other possibility is that a nearby full power station of sufficient power is getting into your wiring and being re-transmitted by you.
I had a 5 kW station 1-mile away get into my phone line. You could listen to it during phone conversations and it wrecked my DSL internet signal.
RFBurns has given a cure in the form of an inductor which filters out the unwanted station. A filter might help you if you find where it’s getting into your wires.