What happens when antennas at opposite ends of a VHF or UHF line of sight radio link are not using the same polarization?

When antennas at opposite ends of a VHF or UHF line of sight radio link do not utilize the same polarization, the received signal strength is indeed reduced. This occurs because polarization mismatch leads to less efficient coupling of the radio waves between the transmitting and receiving antennas.

In practical terms, antennas are designed to transmit and receive signals in specific polarizations, which can be vertical, horizontal, or circular. When both antennas are not aligned in the same polarization, a significant portion of the signal energy is lost. For example, if one antenna is vertically polarized and the other is horizontally polarized, only a fraction of the signal will be effectively received due to this mismatch, resulting in a weaker signal at the receiver.

This understanding is crucial for optimizing radio communications, particularly in line of sight scenarios where alignment of antennas can play a significant role in the overall efficiency of the communication link. Recognizing the importance of matching polarization can help in ensuring better performance and reliability in VHF and UHF communications.