11 / 20

Atmospheric attenuation of VHF radio transmissions is affected by the characteristics of the transmission and of the air through which it travels. Given a stable, non-changing air pressure, attenuation increases as…

  • A
    frequency increases and air temperature decreases.
  • B
    frequency and air temperature both increase.
  • C
    air temperature increases and frequency decreases.
  • D
    air temperature and frequency both decrease.

Attenuation is the term given to the loss of signal strength in a radio wave as it travels outward from the transmitter. It limits the range of radio signals.

We can say that attenuation is affected by a number of factors including:

  • The materials a signal travels through => the higher the density of the material – the higher the attenuation.
  • Frequency and wavelength => higher frequencies and lower wavelengths suffer from higher attenuation – because they have a higher number of peaks which causes a higher number of energy fluctuations and energy loss over distance, being more prone to attenuation.
SUMMARY:
Attenuation increases as:
  • air density increases
  • wavelength decreases
  • frequency increases
  • air temperature decreases
Note: with regards to the air, provided that pressure remains constant – the lower the temperature, the higher the density => attenuation increases with temperature decrease.

Your Notes (not visible to others)



This question has appeared on the real examination, you can find the related countries below.