T3A04 - What happens when antennas at opposite ends of a VHF or UHF line of sight radio link are not using the same polarization?

Question

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

Answer Options

  • A) The modulation sidebands might become inverted
  • B) Received signal strength is reduced
  • C) Signals have an echo effect
  • D) Nothing significant will happen

Correct Answer: B


Explanation

If a transmitting antenna is vertically polarized but the receiving antenna is horizontally polarized (or vice-versa), the polarization mismatch prevents the receiving antenna from efficiently coupling with the incoming wave’s electric field. The receiving antenna only picks up a small fraction of the available signal.

This mismatch causes a severe loss in signal strength, meaning the received signal strength is greatly reduced. In theory, the loss can be total, but in real-world environments, reflections usually scatter the signal enough that a small amount is still received, though often not enough for a solid contact.


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