Ignition interference problem

[6banger]

I put a used power antenna on my `87 and now I have interference on the stock radio when the car is running. I`m not sure if I had this problem this bad last year, (I just took the car out of storage).
But, now this is what really has me lost, I had my handheld VHF Marine radio (battery operated) with me to get the latest weather conditions for fishing, and it too is affected! I shut the engine off and the reception is fine on both radios.
Last year we replaced the wires, plugs,and module with GM parts.
Any info would be appreciated.

Thanks,
Jim

Lucky Dog Charters , Lake Michigan Sport Fishing

 

[GNandTTA]

Make sure all grounds are good (battery to engine, ign module to engine, and fender to firewall, engine to firewall) Usually interfance as you describe is caused by a bad ground.