Horizontal radiations are bad received by the FM antennas, since the antennas are vertically aligned.
When you are often in areas where you receive horizontal signals, you will need a horizontal receiver on your UKW antenna. This begins by 3 horizontally mounted rods and receive horizontal field lines. It is simply put over your existing VHF antenna. However, it only works with Steel rods VHF antennas and not with plastic hard antennas.