Yes, your noise is antenna ground related. That is the factory antenna so it will have a connection inside the passenger kick panel that often oxidizes. Find it and twist the bejesus out of it to clean the connection. That will help. The connector is not made to be taken apart once connected, so dont try or you will end up buying a whole new antenna. Spray it with electrical contact cleaner if you have some. Next, make sure the antenna head is mounted tight. There were two different types in that era, one simply clamped the top and bottom escutcheon against the fender with a nut on top to tighten it all together with a pretty chrome washer on top and done. The other was for the narrow fender cars and had two 7mm (9/32) screws that held the base to the inside lip of the fender as well as the nut to tighten the pretty chrome washer on top. Make sure the antenna base has a good solid ground to get rid of antenna static.