The reflected wave  

Electromagnetic waves reflect from earth’s surface and from conducting objects like wires and steel beams. The reflected wave travels farther than direct wave. The 2 waves are usually not in phase at receiving antenna. If they are equally strong but 180 °out of phase, a dead spot occurs. This is most usual at the highest frequencies.

                                                          Figure--The reflected wave travels farther than direct wave.


At VHF and UHF, an improvement in reception can result from moving transmitting or receiving antenna a few inches. In mobile VHF/UHF operation,  when transmitter or receiver are moving, dead spots generate holes or picket fencing in received signal.