I have a 2meter 5/8 wave mag and a 10meter mag both on the roof of a 1990 Sedan DeVille. The problem is that going down the highway these things sing at a most annoying frequency and level. Operating is not affected but the operator is. A friend of mine suggested wrapping a piece of tape in around the whip so it forms a flag. The tape is plaved between 1/2 and 2/3 up the antenna. I tried it and it didn't work. I have applied a longer flag to each whip with hopes that will work.
Anyone have any other ideas?